TRANSYT 14 User Guide.pdf

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TRL

APPLICATION GUIDE 65 (Issue J)

TRANSYT 14 USER GUIDE

By James C Binning, Mark Crabtree, Graham Burtenshaw.

Copyright TRL Limited 2010, 2011. All rights reserved.

Certificate No FS 567469

Software manufactured under an ISO 9001registered quality management system

TRL SoftwareCrowthorne House

Nine Mile RideWokingham Berkshire

RG40 3GA United Kingdom

Tel: +44 (0)1344 770758

Fax: +44 (0)1344 770356E-mail:[email protected]

www.trlsoftware.co.uk
mailto:[email protected]:[email protected]:[email protected]://www.trlsoftware.co.uk/http://www.trlsoftware.co.uk/http://www.trlsoftware.co.uk/mailto:[email protected]


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TRANSYT 14 User Guide (Issue J)

The information contained herein is the property of TRL. Whilst every effort has beenmade to ensure that the matter presented in this document is relevant, accurate and up-to-date at the time of publication, TRL cannot accept any liability for any error oromission.

The copyright in this material is held by TRL Limited and cannot be used for commercial gain orreproduced unless authorised/licensed by TRL Limited.

First Published 2010

ISSN 1365-6929

SCOOT is co-owned by Peek Traffic Ltd, TRL and Siemens Traffic Controls Ltd.

SCATSis a registered trade mark of the Roads and Traffic Authority of New South Wales inAustralia and other countries

Aimsun is a trademark of TSS-Transport Simulation Systems, S.L.

Aimsun is a product of TSS-Transport Simulation Systems, S.L.

VISSIM is a product of PTV AG

TRANSYT-7F (an adaptation of TRLs original TRANSYT 7 software product) is developed andmaintained by McTrans (University of Florida).

Windows, Windows XP, Windows Vista, Windows 7 and Outlook are registered trademarksof Microsoft Corporation.

WinZip is a registered trademark of WinZip International LLC.

Other products and company names mentioned herein may be the trademarks of their respectiveowners.


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ABSTRACT OF APPLICATION GUIDE 65 2010

TRANSYT is a macroscopic off-line computer program for studying everything from

isolated road junctions to large signal-coordinated networks. TraditionallyTRANSYTs primary role has been the study and determination of optimum fixedtime, co-ordinated, traffic signal timings in any network of roads for which theaverage traffic flows are known. However, TRANSYT 14 is also designed specificallyto be used for the assessment of isolated signal controlled junctions, signalisedroundabouts, partially signalised roundabouts and for any network of non-signalledand signal controlled junctions which influence the behaviour of each others traffic.

A traffic model of the network calculates a Performance Index (P.I.) in monetaryterms, which, in its simplest form, is a weighted sum of all vehicle delay and stops.A number of available optimising routines systematically alter signal offsets and/orallocation of green times to search for the timings which reduce the P.I. to a

minimum value. TRANSYT is the most widely used program of its type throughoutthe world.

This Application Guide provides a comprehensive users guide to the latest versionof TRANSYT software (TRANSYT 14.1) issued by TRL. It has been updated to

include details of the changes made since TRANSYT 13; in particular the addition ofseveral alternative optimisation routines; the use of lanes and traffic streams (TS)as an alternative to the traditional link structure; an enhanced conflict modelallowing conflicts associated with lanes, links, movements or traffic streams; mixingcell transmission models (CTM) and platoon dispersion models (PDM) within thesame network; ARCADY/PICADY based models, and other extensive enhancementsto both the traffic model and the fully-interactive graphical interface.


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TRANSYT 14 user guide

July 2012, Issue J (to accompany TRANSYT 14.1.2)

For program advice, sales and distribution information pleasecontact either TRL Software Sales or your local distributor.

TRL Software Sales:

TRL Software SalesTRLCrowthorne HouseNine Mile Ride

WOKINGHAMBerkshireRG40 3GAUnited Kingdom

--------------------------------------------------------------------

Telephone lines: +44 (0)1344 770758+44 (0)1344 770558

Fax: +44 (0)1344 770356

E-mail: [email protected]

Web site: www.trlsoftware.co.uk

Knowledge base: www.trlsoftware.co.uk/knowledgebase

Latest downloads: www.trlsoftware.co.uk/downloads

--------------------------------------------------------------------

Training courses: www.trlsoftware.co.uk/training

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For traffic modelling, traffic auditing and traffic consultancy servicesplease contact our consultancy team:

Telephone +44 (0)1344 770758

E-mail: [email protected]
mailto:[email protected]:[email protected]://www.trlsoftware.co.uk/http://www.trlsoftware.co.uk/http://www.trlsoftware.co.uk/knowledgebasehttp://www.trlsoftware.co.uk/knowledgebasehttp://www.trlsoftware.co.uk/downloadshttp://www.trlsoftware.co.uk/downloadshttp://www.trlsoftware.co.uk/traininghttp://www.trlsoftware.co.uk/trainingmailto:[email protected]:[email protected]:[email protected]://www.trlsoftware.co.uk/traininghttp://www.trlsoftware.co.uk/downloadshttp://www.trlsoftware.co.uk/knowledgebasehttp://www.trlsoftware.co.uk/mailto:[email protected]


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CHAPTER HEADINGS

1 Introduction........................................................................................ 17

2

Installing the Software......................................................................... 27

3 Modelling Basics.................................................................................. 30

4 Optimisation Basics.............................................................................. 49

5 How to use TRANSYT 14....................................................................... 51

6 General Graphical User Interface (GUI) operation.................................... 69

7 TRANSYT 14 Input Data....................................................................... 95

8 Other Data Entry Screens................................................................... 105

9 Network Construction Editor (NetCon).................................................. 133

10 Working with Analysis Sets, Demand Sets and Time Segments........... 163

11 Working with Traffic Flows.............................................................. 169

12 Working with Traffic Signals........................................................... 195

13 Working with Priority Junctions....................................................... 229

14 Working with Traffic Models............................................................ 273

15 Working with Results..................................................................... 277

16 Generating Reports ....................................................................... 295

17 TRANSYT 14 Outputs..................................................................... 303

18 X-Y Graph Analyser....................................................................... 323

19 Additional Tools and Features......................................................... 331

20 Traffic Behaviour Models (PDM/CTM/CPDM)...................................... 337

21 Traffic Model Features in Detail....................................................... 351

22 Optimisation in detail..................................................................... 383

23 Modelling Examples....................................................................... 401

24 Modelling Signalised Roundabouts................................................... 411

25 Definitions / Glossary..................................................................... 439

26 References................................................................................... 457


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CONTENTS

1 Introduction........................................................................................ 17

1.1 About TRANSYT........................................................................... 17

1.2 Summary of TRANSYT 14 improvements......................................... 19

1.3 About this manual........................................................................ 20

1.4 Training...................................................................................... 21

1.5 Student Edition............................................................................ 21

1.6 Related Software......................................................................... 22

1.7 Product Background and Versions.................................................. 22

1.8 News-feeder, Updates and Download system.................................. 24

1.9 Acknowledgements...................................................................... 24

2 Installing the Software......................................................................... 27

2.1 Hardware/software requirements................................................... 27

2.2 Installing/uninstalling the software................................................. 27

2.3 Copy-protection and software registration....................................... 27

3

Modelling Basics.................................................................................. 30

3.1 Traffic Model Basic Assumptions.................................................. 30

3.2 Network representation................................................................ 30

3.3 Relationship between lanes and TRANSYT links................................ 31

3.4 Relationship between lanes and traffic streams................................ 33

3.5 Flow, speed and link/stream/lane data........................................... 35

3.6

Signal settings............................................................................. 37

3.7 Traffic behaviour within a link or traffic stream................................ 43

3.8 Delays, Queues and Stops............................................................ 43

3.9 Maximum queues......................................................................... 44

3.10

Give-way situations...................................................................... 46

3.11 Shared stop lines......................................................................... 46

3.12

Flared Approaches (and CPDM)...................................................... 47


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3.13 Flared Approaches (and Quick PDM)............................................... 47

4 Optimisation Basics.............................................................................. 49

4.1 Network timings optimisation........................................................ 49

4.2 Cycle Time optimisation................................................................ 49

5 How to use TRANSYT 14....................................................................... 51

5.1 Essential GUI terms you need to know............................................ 51

5.2 Quick start for TRANSYT users....................................................... 51

6 General Graphical User Interface (GUI) operation.................................... 69

6.1 General...................................................................................... 69

6.2 Getting help................................................................................ 69

6.3 Accessibility................................................................................ 70

6.4 Demo (and Viewer) mode............................................................. 70

6.5 Advanced Mode........................................................................... 71

6.6 Speed of operation and large files.................................................. 71

6.7

Main toolbars.............................................................................. 72

6.8

Changing the Active Data Item...................................................... 75

6.9 Padlock system............................................................................ 76

6.10 The 'Edit in Window' System......................................................... 78

6.11 Types of Data.............................................................................. 79

6.12 Running Files and using Auto-Run.................................................. 84

6.13 Managing files............................................................................. 85

6.14

Undo/Redo.................................................................................. 87

6.15 Copying data to the clipboard........................................................ 88

6.16 Printing...................................................................................... 88

6.17 Managing Windows...................................................................... 88

6.18 Preferences Screen...................................................................... 91

7 TRANSYT 14 Input Data....................................................................... 95

7.1

Data Files................................................................................... 95


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7.2 Library Files................................................................................ 95

7.3 Data Outline................................................................................ 96

7.4 Data Outline Screen..................................................................... 99

7.5 Data Editor Screen..................................................................... 100

7.6 Data Grids ................................................................................ 101

7.7 Network Construction Editor (NetCon).......................................... 101

7.8 Task List................................................................................... 101

7.9 Data Field Finder ....................................................................... 102

8 Other Data Entry Screens................................................................... 105

8.1 Data Grids ................................................................................ 105

8.2 Query Builder............................................................................ 115

8.3 Main (Common) Data Screen....................................................... 118

8.4 Signals Data Screen................................................................... 120

8.5 Links Data Screen...................................................................... 127

8.6

(Traffic) Streams Data Screen..................................................... 131

9

Network Construction Editor (NetCon).................................................. 133

9.1 Speed of operation..................................................................... 134

9.2 Moving around the network......................................................... 134

9.3 Saving, using and managing Views............................................ 135

9.4 Printing, copying and exporting................................................... 135

9.5 Representation of Links, Lanes and Stop Lines............................... 136

9.6

Manipulating items..................................................................... 138

9.7 Viewing and visualising data in NetCon......................................... 142

9.8 Other toolbar buttons................................................................. 156

9.9 NetCon Options screen............................................................... 157

9.10 Other NetCon Features............................................................... 161

10 Working with Analysis Sets, Demand Sets and Time Segments........... 163


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11 Working with Traffic Flows.............................................................. 169

11.2 Flow Consistency Diagram.......................................................... 171

11.3 Flow Allocation Tool.................................................................... 174

12 Working with Traffic Signals........................................................... 195

12.1 Introduction to traffic signals in TRANSYT 14................................. 195

12.2 Overview of Signal Timings......................................................... 201

12.3 Timings Diagram....................................................................... 210

12.4 Intergreen Matrix Screen............................................................ 220

12.5 Stage Sequence Screen.............................................................. 225

12.6 Phase Delays............................................................................. 227

12.7 Start/end displacements............................................................. 228

13 Working with Priority Junctions....................................................... 229

13.1 What is a Priority Object?............................................................ 230

13.2 Using a Priority Object library file................................................. 231

13.3

Applying a T-Junction Priority Object to an existing network............ 232

13.4

Using an Arm, Traffic Stream and Lane Structure........................... 237

13.5 Steps required using arms, traffic streams and lanes...................... 237

13.6 Movements and Conflicts............................................................ 240

13.7 Visibility Adjustment .................................................................. 244

13.8 Using Links to define your priority junction.................................... 244

13.9 Modelling roundabouts................................................................ 247

13.10

Using Links to define your roundabout...................................... 251

13.11 Mutual opposition................................................................... 253

13.12 Modelling variations of give-way............................................... 253

13.13 Give-ways within signalled junctions......................................... 259

13.14 Give-way simplifications you can make...................................... 269

13.15 Indirect traffic control and give-way bottlenecks......................... 270

14

Working with Traffic Models............................................................ 273


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14.1 Traffic Model selection................................................................ 273

14.2 Vehicle-In-Service and the Random Parameter.............................. 274

14.3 Setting Cell Saturation flows....................................................... 276

15 Working with Results..................................................................... 277

15.1 Summary Results Screen............................................................ 277

15.2 Detailed results ......................................................................... 278

15.3 Animation controls..................................................................... 280

15.4 Graphs..................................................................................... 281

15.5 Time Distance Diagram............................................................... 287

16 Generating Reports ....................................................................... 295

16.1 About Report Files...................................................................... 295

16.2 Report Viewer ........................................................................... 296

16.3 Reporting Options...................................................................... 298

16.4 Using custom grid layouts in reports............................................ 299

16.5

File Comparison Utility................................................................ 299

17

TRANSYT 14 Outputs..................................................................... 303

17.1 Traffic model predictions............................................................. 303

17.2 TRANSYT individual link or traffic stream predictions...................... 306

17.3 TRANSYT network-wide results.................................................... 318

18 X-Y Graph Analyser....................................................................... 323

19 Additional Tools and Features......................................................... 331

19.1

Find Shortest/Best Route............................................................ 331

19.2 Merging Networks...................................................................... 331

19.3 Saturation Flow Estimation.......................................................... 333

19.4 QUEPROB - Effective Flare length calculator.................................. 335

19.5 Drive-on-the-left/Drive-on-the-right............................................. 336

20 Traffic Behaviour Models (PDM/CTM/CPDM)...................................... 337


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22.5 Queue-length reductions ............................................................ 391

22.6 Degree of Saturation limits......................................................... 393

22.7 Controller Stream groups (Node Groups)...................................... 393

22.8 Cycle time selection................................................................... 394

22.9 Cycle Time Optimiser................................................................. 395

22.10 Multiple cycling and repeated greens......................................... 397

22.11 Considering the effect of small changes..................................... 399

23 Modelling Examples....................................................................... 401

23.1 Supplied Data Files .................................................................... 401

23.2 A small network (Example 1)....................................................... 402

24 Modelling Signalised Roundabouts................................................... 411

24.1 About this chapter ..................................................................... 411

24.2 Introduction.............................................................................. 411

24.3 The TRANSYT program............................................................... 412

24.4

Modelling a roundabout (Example 2)............................................ 412

24.5

Checking co-ordination............................................................... 424

24.6 Example 3 a signalised motorway roundabout............................ 425

24.7 Example 4 an urban signalised roundabout................................. 434

24.8 Recommendations ..................................................................... 438

25 Definitions / Glossary..................................................................... 439

25.1 TRANSYT 14 GUI Terms.............................................................. 439

25.2

Modelling and Traffic Engineering Terms....................................... 440

26 References................................................................................... 457

27 Appendix A Import TRANSYT 13 files............................................ 460

28 Appendix B Export to TRANSYT 13................................................ 461

29 Appendix C - Importing from TRANSYT 10/11/12.............................. 462

30 Appendix D Importing from TRANSYT-7F....................................... 464


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31 Appendix E Importing SCOOT data............................................... 468

32 Appendix F Importing SCATS data................................................ 471

32.1 Creating data files from SCATS data............................................. 473


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Installing the Software Page 17


Introduction1

The timings of signals at road junctions have an important effect on the levels of traffic congestion

not only at the junction itself but at surrounding junctions which may or may not have signalsthemselves. Often the junctions in urban areas form part of a network of co-ordinated signalisedjunctions. By co-ordinating groups of signals within a network, substantial reductions can bemade to queues and delays. Each group of signals are operated on a common cycle time. Theirrelative green times are set so that known average volumes of traffic can travel through the urbanarea with as little delay and as few stops as possible.

About TRANSYT1.1

TRANSYT is a macroscopic off-line computer program for studying everything from isolated roadjunctions to large signal-coordinated networks. Traditionally TRANSYTs primary role has been thestudy and determination of optimum fixed time, co-ordinated, traffic signal timings in any network

of roads for which the average traffic flows are known, for which it is recognised internationally.However, TRANSYT 14 is also designed specifically to be used for the assessment of isolated signalcontrolled junctions, signalised roundabouts, partially signalised roundabouts and for any networkof non-signalled and signal controlled junctions which influence the behaviour of each others traffic.

The main TRANSYT method has, as shown inFigure 1-1,two main elements; the traffic model andthe signal optimiser.

The model represents traffic behaviour in a network of streets in which one or more junctions arecontrolled by traffic light signals. The model predicts the value of a Performance Index for the

network, for any fixed-time plan and set of average flows that is of interest. The PerformanceIndex is a measure of the overall cost of traffic congestion and is usually a weighted combination

of the total amount of delay and the number of stops experienced by traffic.

The optimisation process adjusts the signal timings and checks, using the model, whether theadjustments reduce the Performance Index or not. By adopting only those adjustments whichreduce the Performance Index, subject to a number of constraints, such as minimum green,signal timings are successively improved. The model also provides for give-way priority control

possibilities, including the modelling of opposed offside-turn traffic within signalled junctions andfully unsignalised junctions which are influenced by nearby signals.

Signalised and partially-signalised roundabouts can be modelled and their delay minimised by

calculating timings which reduce blocking-back by keeping the circulating carriageway freeflowing.

TRANSYT, at the time of writing, can model up to 200 nodes and 1000 links within a network.TRANSYT is suitable for both drive-on-the-left and drive-on-the-right operation.


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Figure 1-1 The basic structure of the TRANSYT program

Many of the principles behind TRANSYT 14 are essentially the same as those at the heart ofprevious versions of the program. However, TRANSYT 14 brings with it a number of significantmodelling changes as well. All of these changes are described in detail in other chapters.

Although existing users of previous versions will identify many modelling changes, concessionshave also been made to those familiar with previous versions of TRANSYT, where we thought it isuseful to do so.


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Summary of TRANSYT 14 improvements1.2

This section allows existing users of TRANSYT 13 to quickly familiarise themselves with what has

changed and what new facilities have been added to TRANSYT 14 by summarising the changesand improvements. Full descriptions of the changes are to be found in other chapters.

Modelling:

Traffic Stream and Lane networkrepresentation

Blocking back and platoon dispersionmodelled in the same network

Link-by-link selection of traffic models

Mutual opposition modelling

Enhanced opposed offside-turn model

Complex flare/blocking model

Improved modelling of oversaturatedconditions

Links controlled by up to two phases

Signal controller phases

Separate controller streams

Zero flows allowed

Conflicts defined by movement, link ortraffic stream

amber times definable per phase

Major & minor links with different conflicts

RR67 saturation flow estimation per lane

Constant red or constant green signals

Updated (WebTag-based) fuel consumptioncalculation

other minor modelling enhancements

adjustable PCU length

Local OD Matrix traffic allocation using new

Lane Balancing option

New Wide-Area OD Matrix traffic allocationusing Journey Time Equilibrium

Enhanced Priority Object model

Calculation of Dutch TxC values

Graphical User Interface:

File comparison tool

PDF and Word format reports

Enhanced CFP graph

Enhanced X-Y Analyser graph

Easier manipulation of stage sequences

Choice of stage or phase basedmanipulation of signal timings

NetCon PDM flow animation

Various NetCon improvements

Signal Terminology choice (UK/Aus)

Data File Library (template) system withgraphical preview screen.

Collection of library files covering the mostcommon junction layouts

User-defined relative offsets

Improved data-entry screensEnhanced Time Distance Diagram

Locking of analysis sets and demand sets

Various other graphical interfaceimprovements

Instant mirroring of data files

Third-party product flow data import

Export to TRANSYT 13

Basic and Advanced modes of operation

Student Edition

Shaped source connectors

Enhanced Flow Consistency Tool

New Window Manager

Window Docking system

Enhanced Summary Results window

Multiple saveable network Views for bothNetCon and the TRANSYT Report


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Optimisation:

Phase and stage minimums and maximums

Sophisticated stage and phase optimisationAlternative optimisers (Shotgun Hillclimband Simulated Annealing) for improvingtimings

Too high and too low link DoS penalties

Green splits locking

*needs ARCADY 7 or later and/or PICADY 5 or

later

Priority Junctions:

Priority junction objects calculate give-waycoefficients (slope & intercept)*

Assigning of calculated slope and

intercepts to links or traffic streams*

Fully unsignalised junction modelling*

Models one-way situations

Unlimited conflicts on give-ways

Modelling of indirect traffic control effectsat give-ways

Give-ways controlled by mix of signal

controlled and unsignalled traffic

For those wishing to evaluate the differences between TRANSYT 14 and earlier versions, such asTRANSYT 12, we recommend you contact TRL who will be more than happy to explain whateverfeatures you are most interested in.

Many other features

Please browse through this User Guide for information about the

many new features in TRANSYT 14, looking for the followingsymbol:

About this manual1.3

The coverage of this user guide is comprehensive and is intended for anyone who is likely to beinvolved with the use of TRANSYT 14. It is hoped that new users will quickly understand theprogram by reading, and by reference to this manual.

To achieve these aims, this user guide describes, in separate chapters, how to get startedquickly with TRANSYT 14 (particularly if you are already familiar with previous versions), data-entry including full details of all the features of the graphical interface, the theory and researchincorporated in TRANSYT and how a TRANSYT model should be specified (including guidance on

how to measure data). Also described is the output and how it should be interpreted. A numberof examples have been included to aid in the understanding of individual junctions and themodelling problems they pose.

Whilst it is desirable to read as much of each chapter as possible, it is accepted that sufficienttime will not always be available. Hence the earlier chapters concentrate on all the essentialsneeded to get started with TRANSYT, with reference within these earlier chapters to othersections of the guide where necessary.


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The following icons are used throughout to highlight relevant points about the topics beingcovered.

is used to emphasise important points;

is used to warn of the consequences of doing something wrong;

is used to highlight features in TRANSYT 14 that are new to TRANSYT

In many places it is inevitable that jargon will have been used, which include general trafficengineering terms, specific TRANSYT terms and terms relating to features of the graphical

interface. To help avoid repeated explanation of such words and phrases a glossary of terms isincluded (see Chapter25).

The graphics within this document assume drive-on-the-left situations. However, the termsnearside and offside have been used throughout, instead of left or right to allow

understanding for both drive-on-the-leftand drive-on-the-rightsituations.

Training1.4TRANSYT, by its very nature, is a complex software product. Although we try to make ourproduct as easy to use as possible, and also provide this comprehensive user guide, weacknowledge the demand that will exist for training courses and the benefits that training can

provide to both those totally new to TRANSYT and also existing users.

TRL run training courses for many of the software products it sells, including hands-on courseson TRANSYT. We use the most recent releases of our products and we use only experience

trainers usually TRL members of staff who have many years of experience. As the developersof TRANSYT we can offer unrivalled training in its use.

Details of available courses are advertised on our website:www.trlsoftware.co.uk/training

Student Edition1.5

A student version of TRANSYT is available in addition to the full version. This version has thesame functionality of the standard version, apart from one specific limitation Data files saved

from within the student version cannot be loaded into the full version.

Several screens, including NetCon, are watermarked so as to easily identify it as a studentedition. The TRANSYT reports are also watermarked and the header information also indicates

the report has been produced with a student edition.
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Details on availability and pricing can be obtained from TRL Software Sales or your localdistributor.

Related Software1.6

TRANSYT is only one of a number of thoroughly researched and developed traffic-relatedsoftware products that TRL produce and market commercially. TRL software products are

validated against a wealth of real life data and used world-wide. Those products which arerelated to TRANSYT or most relevant to those using TRANSYT are listed below:

TRANSYT-VISSIM LINK is an award-winning* software tool that imports a VISSIMnetwork into TRANSYT and then uses the TRANSYT signal optimiser in conjunction with theVISSIM model to produce an optimum set of signal timings. Furthermore, it can be used tovisualise, validate and edit signal plans for a VISSIM network. *ITS (UK) 2009 ForwardThinking award for innovation. Versions are available for TRANSYT 13 and TRANSYT 14.

TRANSYT-Aimsun LINKis a software tool that imports an AIMSUN network into TRANSYTand then uses the TRANSYT signal optimiser in conjunction with the AIMSUN model to producean optimum set of signal timings. Furthermore, it can be used to visualise, validate and editsignal plans for an AIMSUN network. Versions are available for TRANSYT 13 and TRANSYT 14.

PICADYis for predicting capacities, queue lengths and delays (both queueing and geometric)at unsignalised major/minor priority junctions. It is an aid in designing new junctions as well asassessing the effects of modifying existing designs. PICADY includes accident prediction.

ARCADYis for predicting capacities, queue lengths and delays (both queueing and geometric)at roundabouts. It is an aid in designing new junctions as well as assessing the effects of

modifying existing designs. ARCADY includes accident prediction.

OSCADY PROis designed to model isolated (uncoordinated) signalised junctions. It is usedto assess performance of junctions in terms of capacity, queue lengths and delays. One of itsmany key features is its phase-based optimisation of signal timings to minimise delay, ormaximise capacity by automatically selecting suitable stage orders and associated phasesequences. This allows very quick assessments of both simple and complex cases to be made.

Data import from, and export to TRANSYT is provided.

OSCADY CLASSIC is (like OSCADY PRO) designed to model isolated (uncoordinated)signalised junctions, but optimises using a stage-based approach. This product has beensuperseded by OSCADY PRO.

All these programs are concerned only with the optimisation and operational performance ofindividual junctions or networks. For the overall economic appraisal of wider based road

schemes, an economic appraisal tool will be required.

For further details of all these programs, and for latest news, current pricelists and purchasinginformation, please visitwww.trlsoftware.co.uk.

Product Background and Versions1.7

Investigations carried out in the UK into possible improvements in traffic control of urban

networks in the 1960s resulted in the development of TRANSYT/1 in 1967 by the Transport
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Research Laboratory (TRL). Two trials of TRANSYT were carried out one in Glasgow andanother smaller one in West London. The full-scale Glasgow trials were carried out with thecooperation of the City Council in Glasgow. TRANSYT signal timings went live in May 1967.

TRANSYT was shown to reduce the average journey times through the network of signals in

Glasgow by about 16 per cent. A similar reduction was recorded in the other smaller trial inLondon. Because of TRANSYTs international appropriateness, TRANSYT is now one of the mostwidely used signal timing programs in the world.

TRANSYT has continued to be developed by TRL ever since its first release. TRANSYT 14represents another significant advancement of the product in terms of its traffic models, itsfeatures, and its presentation.

TRANSYT 14.0 (released in October 2010) is the first release of TRANSYT 14.

TRANSYT 14.11.7.1

TRANSYT 14.1 was released in December 2011. Details of subsequent maintenance releases areavailable atwww.trlsoftware.co.uk.

Major changes introduced for TRANSYT 14.1 are indicated in the User Guide in the same way asthose changes made since version 13, using the New icon. For those who are only interestedin the changes since 14.0, a summary of the changes is given below:

New Wide-Area OD Matrix traffic allocation using Journey Time Equilibrium (section11.3.2)

Local OD Matrix traffic allocation using new Lane Balancing option (section11.3.3)

Priority Object now models one-way traffic at T-junctions (section13.3.1)

New results output for each combined CPDM flared area (section21.7.2)

Netcon: Shaped source connectors (section9.6.9)

Netcon: Traffic Model Type overlay (section9.7.4)

Multiple saveable network Views for NetCon and HTML Report (section9.3)

Basic and Advanced modes of operation (section6.5)

Student edition (see section1.5)

New Window Manager plus user-defined default layout of windows (section6.17.1)

New window docking system (section6.17.2)

Improved Main Data, Link Data and Traffic Stream data-entry windows

Easier configuration of Lanes within Traffic Streams (section9.6.9)

TRL Default Custom Grids (section6.7.4)

Report results grouped by controller stream (section16.3.1.4)

Flow Consistency Tool for Traffic Streams (section11.2)
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Position within HTML Report now retained

Enhanced Summary Results window (section15.1)

Amber times definable per phase

Calculation of Dutch TxC values

Network and stand-alone copy-protection versions in same install package (section2.3)

Registration of ARCADY and PICADY products via TRANSYT (section2.3)

Automatic recognition of both network and standalone licensed versions of ARCADY and

PICADY

Improved selection of text data for display in NetCon (section9.9.2)

News-feeder, Updates and Download system1.8

It is useful to the user of any product to know whether or not the particular release they areusing is the most up-to-date available. In order to provide this information automatically, on

launching TRANSYT, it will try to connect to the TRL Update Information Server. If thisconnection is achieved and/or permitted by the user (permanently or as a once-off), the bottomhorizontal status bar will display news concerning TRANSYT such as NEW TRANSYT 13.1.0.63Version Available (as shown below) or No Update Information Available

The displayed text is simply the title of the full information available on our server. Clicking onthe link will bring up the full message.

Connecting to the update information server DOES NOT RESULT IN THEINSTALLATION ANY SOFTWARE, nor does it affect your installation or operation of

TRANSYT including cancelling the link and/or ignoring the messages. We wouldhowever recommend that messages that indicate a new release is available areread and acted upon, as new releases may contain new features and repairswhich users will benefit from.

If, as matter of course, you normally have to enter a username and/orpassword to gain access to, say, the internet on your PC, it will be THISpassword and user name you will need to enter to initially gain access to

our server. This information is securely encrypted within the users localprofile and is NOT tracked, recorded, or used by TRL, and its only purposeis to allow your own PC to easily access this one particular (TRL) server.

If having read about a new release you wish to download it, current maintenance holders can goto the TRL download system at http://www.trlsoftware.co.uk/downloads and follow theinstructions on the web page.

Acknowledgements1.9

The work described in this report was carried out in the Transportation Divisionof the Transport

Research Laboratory. The authors are grateful to all those who carried out the development,
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technical reviews, auditing and testing of this software product. The authors are also grateful forthe documentation associated with earlier versions of TRANSYT and to their authors.

The authors also thank the Department for Transport, Energy and Infrastructure, South Australia

for providing advice on creating the required data files from SCATS for subsequent import toTRANSYT.


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Installing the Software2

Hardware/software requirements2.1TRANSYT 14 will run on any modern PC under Windows 7, Windows Vista or Windows XP and assuch there are no specific hardware or software requirements other than those of a modern PCcapable of running standard Windows desktop applications.

As may be expected, the program will run more smoothly on a PC with a fast processor andplenty of RAM; this will be particularly noticeable if working with large networks and/or using theCTM traffic model.

Recommended hardware and software requirements are as follows:

A PC with a 2.0 GHz processor or faster Windows 7 / Vista / XP (32-bit or 64-bit) 3 GB RAM

250 MB available hard disk space. A monitor with a resolution of 1280x1024 or higher. N.B. A wide-screen or dual monitor

display can also be very useful. a modern graphics card with hardware accelerated OpenGL capability

TRANSYT 14 may run on versions of Windows other than Windows 7/Vista/XP but this is notguaranteed and is not formally supported.

Installing/uninstalling the software2.2

To install the software, browse the product CD for SETUP.EXE, and run this file. This will launch

the product installer. If you have been supplied with the product as a zip file, extract all thezipped files to a temporary folder, and then run SETUP.EXE from this temporary folder.

During installation, all necessary files are copied to the specified folder and an entry added tothe Windows Start menu.

To uninstall the software, please use the Windows Add/Remove Programs system, which isavailable from the Windows Control Panel.

Copy-protection and software registration2.3TRANSYT is a copy-protected software product. Having installed TRANSYT it will initially run in a

DEMO state and in order to use the full product you must register it withthe TRL SOFTWARE.

Moving the system date of your PC backwards is likely to un-register anyregistered versions of this product.


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There are currently three states of TRANSYTs copy protection system stand-alone copy-protection,networkcopy-protection (concurrent licence version) andDemo/Viewer. Usually,versions are licensed on a per-site basis. Licences may also be time-limited, i.e. a Leased or

Evaluation licence.

Both the stand-alone and network copy-protection states are contained within thesame installation package, and the selection of which type to register (Network orStand-alone) is part of the installation process. However, your selection mustmatch the licence type you have purchased.

Only the permanent Demo/Viewer version is supplied separately.

Some optional functionality of TRANSYT 14 requires either an add-in module suchas TRANSYT-VISSIM LINK and TRANSYT-Aimsun LINK, or another product to beregistered, such as ARCADY and PICADY. Details of the TRANSYT LINKS are

documented in the separate User Guide provided with TRANSYT. Details of whatadded functionality is accessible if you have either ARCADY or PICADY is describedin section13.1.

ARCADY and PICADY and the TRANSYT LINKS can be registered from withinTRANSYT using the main menu option Help > Licence Manager. Please note thatwhen checking or changing the status of network versions of any of the listed

products, TRANSYT may take a few extra seconds to respond as it awaitsconfirmation of the licence state.

Stand-alone registration2.3.1

Each installation of the stand-alone version of TRANSYT must be registered. Full setupinstructions are available in the file SOFTWARE REGISTRATION.PDF provided with thesoftware.

This document includes instructions on how to transfer your registered product from one PC toanother. Read these before you lose access to your old PC!

Depending on the situation, it is also possible to upgrade licences. This usually happens whenpurchasing the full version of a product after previously leasing it. In this situation the softwarelicence can be upgraded. Again, see the file SOFTWARE REGISTRATION.PDF for fullinstructions

Network copy-protected (concurrent licence) registration2.3.2

The concurrent licence version works only on PCs with access to a LAN network and allows up to

a fixed number of PCs to run the product at the same time. In order to use the full product youmust setup the software as a Network Client.

Full setup instructions are available in the file SOFTWARE REGISTRATION.PDF providedwith the software.


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Demo/Viewer version2.3.3

This version is described in section6.4.

It can be downloaded for free from here: www.trlsoftware.co.uk/downloads. No download isrequired simply enter your contact information and then select the TRANSYT Demo todownload.

This demonstration version cannot be registered. If you subsequently purchaseTRANSYT you will need to obtain a new version which you can then register.
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Modelling Basics3

This chapter gives an overview of the TRANSYT traffic model. Existing users of TRANSYT can

probably skip this chapter, other than those sections marked with the NEW symbol. Detailshave been kept to a minimum in order to keep the emphasis on getting to know how to useTRANSYT quickly, providing just enough background prior to using TRANSYT. However,TRANSYT is a complex program, so there are many references to the other chapters throughoutthis one. These chapters will still need to be read in order to be able to correctly model specificnetwork features, such as flares.

Note: It is assumed that the reader is familiar with traffic engineering terms such asphase,stage and stage sequence. For those new to the subject, or wishing to clarify, please seesection25.

Traffic Model Basic Assumptions3.1

TRANSYT makes the following assumptions about the traffic situation:

1. There is a cyclical nature to the traffic flows in the areas of the network wherethere are traffic signals. (Unsignalled junctions can be set to assume randomarrival patterns).

2. All the signals in the network have a common cycle time or a cycle time a half,third or quarter of this value; details of all signal stages and their minimumperiods are known.

3. For each distinct traffic stream flowing between junctions, or turning at

junctions, the flow rate, averaged over a specified period, is known and assumedto be constant1.

Network representation3.2

TRANSYT 14 offers the users a choice of how to represent the real network being modelled either using a series of nodes interconnected by links; nodes interconnected by traffic streams;

or a mixture of both.

When using both traffic stream representations and link representations withinthe same network, each differently-represented part of the network must be

connected with a simple one link into one stream or one stream intoone link. That is the only restriction. You can have as many discrete sectionsof the network build with the two structures as you like.

Additionally, each signalled intersection is represented by at least one controller stream. Eachdistinct one-way traffic stream leading to a node is represented either by a link or by a TRANSYT

traffic stream. A TRANSYT traffic stream is made up of one or more TRANSYT lanes.TRANSYT lanes will in general have a one-to-one relationship with real lanes on-street.

1time varying traffic conditions can also be modelled in TRANSYT


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Modelling Basics Page 31


Relationship between lanes and TRANSYT links3.3

The relationship between real traffic lanes and TRANSYT links depends on how traffic uses the lanes

on the road. A single link may be used to represent one or more traffic lanes. Traffic on one

approach may be represented by one or more links.

In general, one link is required to represent each distinct queueing situation that occurs. Thus,trivial queues may not warrant representation by a separate link. However, a separately-signalledoffside turn traffic stream, with a significant flow, should be represented by a link which is separatefrom the link representing straight ahead traffic. One link may represent two or more lanes,provided that traffic is equally likely to join the queue in any of the lanes and that identical signalindications are shown to these lanes.

This link representation suggests that a detailed knowledge of traffic routing through a network isnecessary to prepare the link diagram. In practice, it is usually sufficient for the traffic engineer to

use his judgement to decide whether traffic entering a section of road during a particular stage

green chooses preferentially a particular direction on passing through the next signal and, if so, theproportions of various turning flows to assign to each link.

The relationship between lanes on the road and the way they are modelled as links is illustrated in

Figure 3-1 and Figure 3-2. Figure 3-3 shows a simple triangular road network. Figure 3-2shows the corresponding diagram of nodes and links. Traffic on the southern approach to Node 1is represented by two separate links because nearside turning traffic (link 13) receives a differentgreen time (because of a filter signal) to the other traffic (link 12) on the approach. On the

northern approach to Node 3 traffic is also represented by two links (31 and 32). This gives amore realistic picture of traffic movements, since offside turning traffic from link 21 is unlikely toturn right again at Node 3 and will chose the nearside lane catering for traffic that is turning left or

going straight on.


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Relationship between lanes and traffic streams3.4

The relationship between real traffic lanes and TRANSYT lanes will be generally a direct one-to-one

relationship, so is inherently simple to define within the TRANSYT model. Each lane is automatically

part of a traffic stream which can be used to represent one or more traffic lanes. The definition oftraffic streams depends on how traffic uses the lanes on the road. Traffic on one approach may berepresented by one or more traffic streams.

In general, one traffic stream is required to represent each distinct queueing situation that occurs.Thus, trivial queues may not warrant representation by a separate traffic stream. However, aseparately-signalled offside turn traffic stream, with a significant flow, should be represented by aTRANSYT traffic stream which is separate from the traffic stream representing straight aheadtraffic. One traffic stream may represent two or more lanes, provided that traffic is equally likely to

join the queue in any of the lanes and that identical signal indications are shown to these lanes.

Just like the alternative TRANSYT link representation, the traffic stream representation suggests

that a detailed knowledge of traffic routing through a network is necessary to define the trafficstream within the model. Again, in practice, it is usually sufficient for the traffic engineer to use his

judgement to decide whether traffic entering a section of road during a particular stage green

chooses preferentially a particular direction on passing through the next signal and, if so, theproportions of various turning flows to assign to each traffic stream.

The relationship between lanes on the road and the way these lanes are grouped together to formTRANSYT traffic streams is illustrated inFigure 3-3andFigure 3-4. Figure 3-3shows a simple

triangular road network. Figure 3-4shows the corresponding diagram of nodes, traffic streamsand lanes. Traffic on the southern approach to Node 1 is represented by two separate trafficstreams because nearside turning traffic (traffic stream 13/1) receives a different green time

(because of a filter signal) to the other traffic (traffic stream 13/2) on the approach. On the

northern approach to Node 3 traffic is also represented by two separate traffic streams (32/1 and32/2). This gives a more realistic picture of traffic movements, since offside turning traffic fromlink 21 is unlikely to turn right again at Node 3. Finally the westbound traffic arriving from location

3 is represented by one two-lane traffic stream as the queueing situation is likely to be even sincethe straight ahead traffic (a major movement) can utilise both lanes.


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Figure 3-3Network lane structure with fl ows

Figure 3-4Model lane and traf fi c stream structure


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Flow, speed and link/stream/lane data3.5

The TRANSYT model requires each link or TS to be defined in terms of certain parameters. Those

key data values relating to the modelling of traffic behaviour are given here, and those concerned

with signal control are described in section3.6.

Link length(or Traffic Stream length)is the distance between the upstream and downstream stoplines. For links/streams which do not come from an upstream node, e.g. entry links/streams onthe perimeter of the network, it is normal to use a standard length such as 200m, but a zero valuemay be used.

Traffic flows3.5.1

Traffic flows are either specified directly using the method described below or are assigned bythe Flow Allocation Tool. A mixture of these options is allowed, so parts of the network will

typically have assigned flows and others flows entered directly. However any parts of a network

structure defined using lanes rather than links must use the Flow Allocation Tool and itsassociated OD-Matrices data to calculate the traffic flows.

Where a Flow Allocation Tool is used, the OD Matrix data (traffic flows; allocation mode andallocation type selections) is used to calculate and automatically assign values to the Total Flowsand Source Flows within that part of the network covered by that particular OD-Matrix.

The following section describes how flows are assigned directly to links.

Links3.5.1.1

Link flows are specified in theLinks Data screen (Outline: Links > Link n > Link Flows). Flows arenormally specified in vehicles or PCUs per hour. For each link the user must specify the average

total flowalong the link.

Each link may have associated with it auniform flow source. This is a flow source which entersthe link at a uniform rate throughout the cycle. Thus, there is no platooning. It can be used torepresent, for example, uncontrolled flow from a car park. Links feeding into the network from

outside also carry uniform flow but these flow levels are set using the Source Flow andassociated Total Flow for the link. The Uniform Flow Sourceis used only when there are otherupstream flow sources. The uniform flowsource contributes along with the upstream sources togive the total flow, but need not sum exactly (see compatibility of link flows, section3.5.3).

Links that have their flow allocated with traffic from an OD Matrix cannot also have a uniformflow an attempt to set one will result in the value being reset to zero. An extra OD Matrix

Location can be used instead.

Each link can have up to eight upstream links supplying it with vehicles. For each of theseupstream links the flow and the cruise time or cruise speed of vehicles along the link from theupstream source must be specified.

Cruise times and cruise speeds3.5.2

Cruise times and cruise speeds are the un-delayed times (or speeds) for traffic travelling fromeach upstream stop line (for each source (upstream link orTS))to the stop line on the currentlyselected link (or stream). The values used should be those which correspond to actual trafficbehaviour and not an ideal value intended to give good progression; they should represent the

time taken to travel from upstream to downstream stop line, under prevailing traffic conditions,


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when the signal aspects at both ends of the link (or stream) are green. It is possibly better tomeasure cruise time (as opposed to cruise speed) because it ignores any error in link lengthmeasurement, and by measuring over the whole link it automatically takes into account skin-

friction, curves, bottlenecks etc.

Compatibility of link entry and exit flows3.5.3

The sum of inflows to a link or TS need not equal the total flow. This facility is provided because

in practice the flow values will often be obtained from on-street measurements made at differenttimes. TRANSYT automatically increases or decreases by the same proportion all upstream flowvalues so that the total flow is maintained. If the proportional correction is large a message isprinted as a warning but the optimisation proceeds.

The calculation of the proportions of traffic leaving upstream links (or streams) and enteringdownstream links (or streams) are made before the traffic modelling and signal optimisationcalculations. If, in the traffic modelling process, a link (or stream) is oversaturated so that less

traffic leaves than enters, then the downstream volumes are reduced accordingly and the flowsspecified as the Total Flowwill not be maintained.

Saturation flow3.5.4

Saturation flowat a stop line is the maximum rate of discharge from a queue. It can be obtainedby measurement or calculation based on stop line width and other site factors, for further detailssee section19.3or RR67 (Kimber et al, 1986). The saturation flow must be in units consistentwith those used in specifying link (or stream) flows.

If the saturation flow is reduced due to blocking of turning traffic by opposing traffic, then this maybe approximated by increasing the relative start displacementfor the start of green on that link in

theLinks Data Screen (Outline: Links > Link n > Link Signal Data > Green Period n) (see section3.6), or may be modelled more accurately using the give-way facility (see section13.13).

Entry and exit links and traffic streams3.5.5

For entry links (or streams) on the perimeter of the network, having no upstream links (or

streams) but merely a total flow it is recommended, in order to maintain a reasonable estimateof time spent within the network, to input a cruise time (or speed) for travel over the Length oflink(or stream) specified in the Sources Datascreen (Outline: Links > Link n > Sourcesor TrafficStreams > Traffic Stream n > Sources. No source link or TS should be defined.

Exit links are not required by TRANSYT unless using the Flow Allocation Tool to

allocate flows to it, but can be useful if the direction of traffic exiting the network is to beshown graphically. If using traffic streams, exit traffic streams are compulsory. In order tomaintain a reasonable estimate of time spent within the network, a cruise time (or speed)associated with the travel time along the link is required. If you wish the exit link to have noinfluence on either the signal optimisation or on the queue and delay calculations the Link Datascreen option Exclude from Results Calculation can be set. This effectively ensures that the PI

for the link is always zero and that output results, such as the Network Totals, are not affectedby it.

If you do not want any queues to appear on exit links (or streams), both the Restricted Flow

andIs Signal Controlledoptions should also be de-selected. This ensures an infinite capacity(unless using CTM) and indicates to anyone looking at the network that the link (or stream) isbeing used in such a way that it does not act as any form of restriction to traffic flow, or youdont care about what is happening at the downstream end of it. If using CTM, the cell

saturation flow can still affect traffic flow, so should be set to an appropriate value.


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Restricted Flow (Bottleneck) links and traffic streams3.5.6

Bottleneck links or bottleneck TS are unsignalled links which do not give way to other traffic, butare restricted in some way. They are treated as if they are controlled by a 100 per cent green

signal at which a fixed saturation flow is defined. A bottleneck link (or TS) is treated in a similarway to other links (or TS) it is usually associated with a traffic node for display and reportingpurposes (either as a true bottleneck or as part of a priority junction), but no controller stream is

specified as it is not controlled by traffic signals.

Shared links which are bottlenecks are specified in the Links Data > Shared StopLines screen(Outline: Links > Link n), as for signalised links, but the main link still has only a traffic node andno associated controller stream.

Delays and stops are calculated for bottleneck links (or TS) exactly as for other links (or TS),except that the flow leaving the link (or TS) is controlled only by the saturation flow. Thus,uniform delay and stops will occur only if the flow during parts of the IN-profile exceed the

saturation flow. Random-plus-oversaturation delay and stops are calculated in the normal way(see section21.2).

Signal settings3.6

NB for details of the actual implementation in TRANSYT 14, please see sections12and13.13.

TRANSYT signal terminology3.6.1

TRANSYT models the operation of the signal control at each controller stream by reference to

stage change times. A stage change time is a time at which the green signal on one stage isterminated and the change to the next stage green period is initiated; the next stage greenusually commences a few seconds later, following an interstage period. The green time displayedto traffic on any one link may be initiated by any stage change and terminated by any other stagechange.

When considering co-ordination between signal controlled intersections it is necessary to have aconvention which relates the green periods of any one junction to those at the other junctions inthe network. In TRANSYT this is achieved by relating all stage change times to a common,although arbitrary, zero time as shown inFigure 3-5.

The offsetof an intersection is defined here as the stage change time when the change to greenfor stage number 1 is initiated. In this way the offset may be thought of as the start of the cyclefor the node concerned, where the cycle commences with the change to stage 1 and continues

through the other stages in sequence.


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Figure 3-5Illustration of terms offset and difference in offset

If the offset value at one node is subtracted from that at an adjacent node, the difference inoffsetdefines the start of the cycle at one node relative to that at the other and hence definesthe co-ordination along any links connecting the two nodes.

TRANSYT models the response of traffic to the actual signal changes by using effective green

timesas opposed to the actual stage greens as explained later (see section3.5).

The values which must be specified to define the signal timings at the nodes in the network fallinto three groups, as follows.

Signal values for whole network3.6.2

These values are specified in the Main (Common) Data Screen(Outline: Network Options).

The cycle timefor the whole network is specified in seconds.

The effective green displacements, to be applied to the whole network, are specified in seconds.

Both the start and end of effective green used in the model may be made to occur a few secondsafter the actual signal stage change by specifying displacements of fixed duration. Thesedisplacements apply to all links in the network. Figure 3-6illustrates this concept.

The intention is that the displacements specified in theMain (Common) Datarepresent the inertiaof drivers and vehicles in responding to signal indications, compared with TRANSYTsinstantaneous stop/starts. The start displacementcorrects for the time lost accelerating from rest

up to cruise speed. In the UK this value is typically 2 seconds, but a larger value would beappropriate where the red/amber-before-green period is omitted.

1 cycle for node 1

Distance

Time

Arbitary zero for time

Node 1

Node 2

Stage 1 green Stage 2 green

Change to

stage 2

Change to

stage 1

1 cycle for node 2

Stage 1 green Stage 2 green

Change to

stage 1

Change to

stage 2

Distance

in offset

between

node 1 and

node 2

offset for node 2

offset for

node 1


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Figure 3-6Effective versus actual signals

The global end displacement corrects for traffic continuing to flow during the amber-after-greenperiod as though the signal were effectively green. In the UK this value is typically 3 seconds(equal to the full duration of the amber period). TRANSYT models traffic behaviour using effective

green periods which are typically 1 second longer than, and displaced relative to, the actual greensignal.

Additional relativedisplacements may be specified for individual phases - See section3.6.3.5.

Signal values for each controller stream3.6.3

Each controller stream may contain data for up to 50 stages and 50 phases. These values arespecified in the Signals Screen (Outline: Controller Streams > Controller Stream n > Stages).

Phase data, phase delays, a library of stages, a collection of stage sequences and calculated stagesdata relating to each stage used by the traffic model, are all stored within each controller stream.

Each controller stream makes reference to a particular stage sequence (the Use Sequencevalue).The referenced stage sequence can be any sequence in the list of existing sequences for that

controller stream. Stage sequences can be created manually by firstly creating the requiredstages in the Stages library, and then defining the order of stages in a new Sequence. Forconvenience, all possible stages, plus a collection of the ten simplest valid stage sequences can begenerated automatically using a Generate Stages and Sequences routine.

From the above described data TRANSYT calculates internally information relating to each of thestages that is going to be used by the model, i.e. those referenced in the current sequence. Thisinformation is reported under the description calculated Stages.

The Stage change times, part of thecalculated stagesdata,are always shown in seconds.

Green

Amber

D1 D2

Effective green displacement

at start of green

D =

Effective green displacement

at end of green

D =

Red/Amber

Green

Red

Red

Red Actual signal timings

Effective signal timingsRed


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Traditionally TRANSYT stage change timeshave been defined as the times at which a change ofsignal aspect is initiated, as opposed to the genuine start of stage which starts only when thelast phase running in that stage, starts. TRANSYT now uses the later genuine definition;

however, it still reports some resultant timings using the older definition. These are always in

addition to the genuine times and are prefixed with the word TRANSYT, e.g. TRANSYT Stageminimum.

Stage Library, Stage Minimums and Interstages3.6.3.1

For each library stage a minimum green period can be defined. The minimum green period(User Stage minimum) is the time between the start of the last phase starting in that stage andthe earliest time that this stage could end. This would normally be the minimum for the phase

that started last, unless this phase is a turn indicative arrow in which case it could be theminimum of one of the other phases. This value is ignored if it is less that TRANSYTs owncalculated minimum stage length.

The calculated stage minimum, plus the phase minimums and phase maximums all act as

constraints used by the TRANSYT optimisation routines and by the re-distribution or EQUISATroutines, to prevent a stage or a phase having an unduly short or long green time. A combinedvalue in the range of 10 to 15 seconds is normal for vehicular traffic but pedestrian crossing needs

may dictate longer times.

For a pedestrian stage, the minimum green period is the time from the end of the interstageperiod to the end of the green man indication (or the end of the black-out, if used) on thepedestrian stage. Since no traffic flows during the pedestrian stage, the pedestrian stage length

used by TRANSYT, after optimisation, is the interstage timeplus the minimum green period.

Interstages need not be specified as these are derived from the phase intergreensand phase gaining and losing delays. The interstage is specified in seconds and is

defined as starting from the termination of the firstphase to lose green when astage change is made (it also signals the end of the stage) to the commencementof the green for the last phase to receive green in the next stage. TRANSYTproduces an interstage matrix that allows every possible interstage to be viewed,and also edited via the Timings Diagram, if required.

Phase Constraints3.6.3.2

Phase constraints (phase-to-phase Intergreens) are specified via the Intergreen matrixscreen.Additionally, banned stage-to-stage to transitions are also defined here. Other phase data isspecified in the Signals Traffic Stream Data screen (Outline:Arm n >Traffic Streams > TrafficStream n > Link Signal Data) and Links Data screen (Outline: Links > Link n > Link Signal

Data.

Minimum and maximum green times can also be specified on each individual phase in order toconstrain phase lengths to what is required.

Derived Phase Values and Green periods3.6.3.3

During one cycle a link (or TS) may have one or, optionally, two, three or four green periodsduring which outflow occurs. These green periods are determined by the green times associatedwith the controlling phases and need not be the same length, but will have the same value ofsaturation flow.

Links (or TS) may receive green for all or part of one or more stages. The time at which theactual green begins is determined purely by when the phases actually run, and these are

determined by the user by specifying which stages they run, and whether or not there are anyphase delays. Phase delays alter when a phase will start or end relative to the stage it is


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running in This could result in the phase starting early or ending late. N.B. a phase startinglater than any other phase, or finishing earlier than other phase defines the actualstart and end of the stage.

The effective green can be extended by use of a relative end displacement.

Internally, various parameters are derived from the user specified information andused by the TRANSYT model. Some of these parameters can be seen in theResultant StagesData produced by TRANSYT. They may be recognised by users

of earlier releases of TRANSYT, but generally are likely to be of limited interest tousers.

E.g. starting and Ending Stages are derived from the library stage data. Theinternal time at which the actual green begins is specified by a TRANSYT Starting

Stage numberand a start lagof a fixed number of seconds. Similarly, the time atwhich green ends is specified by a TRANSYT Ending Stage Number. The calculated

Start and End lags (used internally by the TRANSYT model) are derived from theuser-specified intergreens and phase delays.

The Starting Stage number defines which of the stage change times starts thechange to the green period on the link (or TS). The start lagthen gives the timein seconds from the stage change time to the start of green signal on the link (orTS). Usually the start lag corresponds to the interstage time, as shown inFigure3-7. TRANSYT adds the displacement of start of effective green (seeFigure 3-6)to this lag to give the time of start of traffic flow assumed in calculating delays etc.

for the link (or TS).

The Ending Stage number defines which stage change time ends the greenperiod. The green periods can run between any stage numbers, e.g. 2 to 3, 2to 6, 7 to 3, or 4 to 4 (in the latter case, the green period will for the complete

cycle).

Following the ending stage, there is the TRANSYT end lag defining the time inseconds from the stage change time to the end of green signal. The sameconsiderations apply as for the start green lag regarding any extra adjustments.

Often this value is zero.

Should the link (or TS) have a second green, the corresponding values detailed above for the firstgreen will also be derived by TRANSYT for the second one.


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Figure 3-7Lag between change demand and start of green signal

Phase Delays3.6.3.4

Phase actual green times are specified relative to the genuine stage start and end times usingabsolute phase gaining and phase losing delays. Relative phase gaining delays can also bespecified, which are relative to the relevant intergreens rather than the stage ends. These valuescan either be entered directly or manipulated graphically in the Timings Diagram. Stage change

times are always needed by TRANSYT, and initial ones can be provided by using the Signal OptionAuto Redistribute orEQUISAT routine from the Tools menu of in the Timings Diagram.

Phase Effective Greens3.6.3.5

As well as the global start and end displacements, additional relative displacements may bespecified for individual phases, if it is thought that the values for that phase differs from theoverall value.

The displacements in the Main (Common) Data and the relative displacements are addedtogether in the program to give the effective green times before the queue calculations arecarried out. For example, if the global network start displacement (see section12.7)is 2 seconds,

and it is known that for the phase being considered, the effective green displacement is one

second longer than the overall value, then the required relative start displacement is simply 1second.

However, all effective displacements are subtracted from the calculated green times beforethese are output in the results (see section 17.2) so that the traffic engineer can easilycompare TRANSYT values with observations of actual green times.

Furthermore, a negative relative start displacement (say -2 seconds) could be used to

justifiably remove or reduce the standard start displacement in situations where goodcoordination has resulted in the front of a platoon of traffic arriving during a green signal.

Amber

Red

Red/Amber

GreenGreen

RedGreenRed Red

Start

LagStart

Lag

Start green on

stage 2

Start green on

stage 1

Demandchange to

stage 2

Demand

change to

stage 1

Stage 1 actual signals

Stage 2 actual signals


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Traffic behaviour within a link or traffic stream3.7

TRANSYT makes use of one of three traffic models. These are the platoon dispersion model

(PDM), the Cell Transmission Model (CTM) and the congested platoon dispersion model (CPDM).

The three models each have their own advantages and disadvantages. The CTM is particularlyuseful for small networks with short links (or TS). Its main advantage is its ability to model theeffects of traffic blocking back from one junction to another reducing the upstream junctionscapacity. The PDM model is suited to all network types and has the advantage of being able tomodel the dispersion of platoons of traffic along links (or TS), but does not model the effects ofblocking back. The CPDM is an adaptation of the PDM model such that it can model specifically

short bays (flares). Full details on these models are given in chapter20and on cyclic flow profilesin Section15.4including advice on choosing the right model to use.

To model traffic behaviour within the network using these models, the common cycle time is

divided into a number of intervals called steps. For convenience, a step is typically set to be onesecond long. How these steps are used depends on the model used.

With the PDM model TRANSYTs calculations are made on the basis of the average values of trafficdemand and queues for each step of a typical cycle. The resultant histograms of traffic arrivals

per step are termed cyclic flow profiles.

The profile of traffic entering a link will be displaced in time and modified during the journey alongthe link due to the different speeds of the individual vehicles. Thus, platoons of vehicles will bepartly dispersed. The amount of dispersion can be modified for individual links.

By selecting the PDM model, TRANSYT automatically takes into account the importance of havinggood progression on short links.

The CTM model also uses steps but is it also discrete in space as well as in time. As a result theCTM cyclic flow profiles are different and are differently presented. The representation of traffic istherefore different to the PDM model.

The CPDM model has an additional blocking capability that allows it to be used to model situationsflared situations. It is used as a direct replacement for the Flare model that was in previous

versions of TRANSYT, but it is more capable. See section3.12

All the models use a simplification of real traffic behaviour, and do not model individual vehicles.Despite this, TRANSYT is able to predict good estimation of traffic delay.

Full details of the data required for these models are given in chapter 1.

Delays, Queues and Stops3.8

Total delay to traffic on a link (or stream) is the sum of the delays to all the individual vehiclesusing the link (or stream) during a period of time. Total delays are usually quoted in units ofPCU-hours/hour. For example, during a cycle of 100 seconds, 40 PCUs pass through a signal.On average they experience 20 seconds of delay each. Thus, the total delay rate is 800PCU-seconds per 100 second cycle (equivalent to 8 PCU-seconds/second or 8 PCU-hours/hour).This delay rate is equal to 8 PCU and can be visualised as the average number of PCUs queueingthroughout the cycle considered. This is strictly true only for the idealised vehicle behaviour that

is assumed in TRANSYT. Nevertheless, this interpretation is a reasonable approximation to whathappens in reality. Similarly, the total delay rate in a network of signals can be considered as


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Page 44


the sum of the average queues at all the stop lines. In TRANSYT, the total delay rate for trafficon a link is obtained partly from the cyclic flow profiles and partly using a simple formula.

When considering the growth and decay of queues, the fact that individual vehicles arrive at

random, and that average arrival rates may vary over the modelled period, means the accuratemodelling of queues is complicated. The problem was studied comprehensively by TRRL (Kimberand Hollis, 1979) and a time dependent method of predicting queues and delays was developed.The method considers the probability distribution of queue lengths as a function of time.

Queue lengths are derived from cyclic flow profiles during each step of the typical cycle. As well asthis uniform component of queue, additional elements associated with random and oversaturatedeffects are added to these. Full details of queue length derivation are described in Section21.2.1.

TRANSYT also calculates the total rate at which vehicles are forced to stop on a link. This too, is

made up of a uniform component and a random-plus-oversaturation component. As for delay,the uniform component is obtained from the cyclic flow profiles and the

random-plus-oversaturation component is calculated from simple equations.

Maximum queues3.9

As part of the calculation of traffic behaviour on a link (or stream), TRANSYT estimates themaximum queue length to be expected with the given signal settings. In reality, on some links(or streams), particularly short ones, the queue may reach back from one junction to another,thereby at least partially blocking the upstream junction. This complex effect is, however, notmodelled in TRANSYTsplatoon dispersion model (PDM) which assumes that all vehicles queue at

the sto

TRANSYT 14 User Guide.pdf

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