San Antonio TransGuide Travel Time Program Roger L. Strain Research Analyst Southwest Research Institute San Antonio, TX [email protected].

San Antonio TransGuideSan Antonio TransGuideTravel Time ProgramTravel Time Program

Roger L. StrainRoger L. StrainResearch AnalystResearch AnalystSouthwest Research InstituteSouthwest Research InstituteSan Antonio, TXSan Antonio, [email protected]@swri.org

Model Deployment Initiative (97-99)Model Deployment Initiative (97-99)

Created area-wide database of travel speeds

– Real time data from instrumented segments of the freeway system

– Arterial street information (incidents, lane closures, segment speeds)

In-Vehicle Navigation (IVN) project

– Transmission of real time link travel speeds and incident data from TransGuide to IVN units using FM subcarrier channel

– IVN units provided point to point travel time estimate as part of route calculation

• Shortest time was one of three options for route selection

– Alpine and Zexel manufactured IVN units• Companies did not market units beyond MDI purchase

Travel Times Public LaunchTravel Times Public Launch

TransGuide automated display of travel times on Dynamic Message Signs (DMS) launched in November of 1999 – Data provided by Data Server process from MDI

No formal outreach program Press Release sent out the Friday before system

was activated– Resulted in stories on each local television news

program

– Front page article in San Antonio Express News

Largely positive reaction as system went live

Travel Times in San AntonioTravel Times in San Antonio

Travel times calculated and displayed from DMS locations to major intersections and/or interchanges

Point travel speeds used to calculate time from detector to detector based on distance between detectors

– Loop Detectors

– Video Detectors

Travel time messages displayed on main lane DMS

– 6:00 AM to 10:00 PM

– Seven days a week

Travel time messages on TransGuide website use the same algorithm

Segment Segment Speed Travel Time

(MPH) (Minutes)1 55 0.552 47 0.643 47 0.644 45 0.675 30 1.006 30 1.007 30 1.008 25 1.209 20 1.5010 15 2.0011 15 2.00

TOTAL 12.19

Travel Time Calculation-

- Segment travel speed is chosen as lower of upstream and downstream sensor speed

- Point to point travel speed is summation of segment travel times

- In this example the DMS is 5.5 miles from the IH 10 interchange, with 11 travel segments defined by 12 sensor locations. For this example, all segments are exactly ½ mile in length, although in the real world the segment lengths vary.

Travel Time AlgorithmTravel Time Algorithm

Display of Travel Time MessagesDisplay of Travel Time Messages

Non Peak Usage– Travel Time messages appear alone

Peak Usage– Travel Time messages can be combined with congestion

warnings– Largely negative public reaction to messages reading only

“CONGESTION AHEAD”– Adding limits and travel times results in more positive reaction

Incident Interaction– Travel Times messages automatically overridden– Can be made second phase of any message with one click

Public Reaction and UsePublic Reaction and Use

Display of travel times on DMS very well received by public

Television and radio stations– Traffic reports use TransGuide web site travel times

regularly

– Station web sites link directly to or incorporate TransGuide web site for travel times and other traffic information

Travel Times messages alleviate public concerns that signs are never used– Still in line with TxDOT policy of displaying only traffic

related messages on DMS

Travel Time AccuracyTravel Time Accuracy

Predictive Algorithms– Experimented with predictive algorithms during development

– Attempted to compensate for speeds increasing or decreasing

– Did not pursue because of low benefit for additional cost

Accuracy– Test runs show approximately 85% of drivers arrive within

predicted travel time range

– Remainder almost evenly split between early and late arrival

Public Confidence– Online surveys indicate greater than 85% confidence

– Public reports quickly when travel times seem wrong

Investment in Travel Time ProgramInvestment in Travel Time Program

Capital investment in TransGuide

– $140,000,000: CCTV, DMS, telecommunications, speed sensors, etc.

Investment in travel time program development

– $60,000: initial development and integration

– $10,000: upgrades and modifications (estimated)

Necessary pieces already in place: Traffic Sensor subsystem, DMS subsystem, Scenario processes

Only Travel Time specific development required

– Relatively short development time

– Relatively small development cost

Travel Time SignificanceTravel Time Significance

Initially Travel Times seemed useful, but not critical Operator Impact

– System automatically recalculates and updates messages once per minute

– After starting system, operators do not have to continually monitor messages

After more than 5 years of operation– Complaints from media when travel times are unavailable– Complaints from the public when travel times are incorrect– Complaints that travel times are not available through

construction zones

Public and media now EXPECT Travel Times, and they expect them to be ACCURATE

Predictive Travel Times- Predictive Travel Times- Government Agency ConcernsGovernment Agency Concerns Policy of providing data to private sector at no cost has

resulted in multiple private sector information sharing agreements, but no real successful examples of private sector data marketing in this area

While predicting congestion and weather related delays in travel time can be done using archived data, predicting incident related delays in travel times will be very difficult

Current investment in travel time program is relatively small, making the case for major investment on government sector side in predictive travel times will be difficult

Travel Times Through Construction ZonesTravel Times Through Construction Zones

San Antonio has begun installing Microwave Radar Detectors in construction zones so that travel times can be determined

Side fire radar units are pole mounted at Right of Way line, have up to 200 ft. range

Wireless radios transmit signal outside of construction zone

Future Travel Time NeedsFuture Travel Time Needs

Intercity travel times– Toll Roads/Managed Lane projects being developed in

many regions statewide, using electronic toll collection is increasing market penetration of AVI tags in Texas

– Installation of AVI readers on rural highways could be used to determine intercity travel times

Alternate route travel times – Encourage trucking industry to take IH 35 bypass, to

avoid San Antonio/Austin traffic between Seguin, Tx and Georgetown, Tx

– San Antonio is in the early stages of toll road implementation, toll lanes will have free alternates, will help to disseminate time savings for those using toll lanes

Contact:

Brian G. Fariello, P.E.Brian G. Fariello, P.E. Roger L. StrainRoger L. StrainTraffic Management Engineer- Traffic Management Engineer- Research AnalystResearch AnalystTransGuideTransGuide Southwest Research InstituteSouthwest Research InstituteSan Antonio District- TxDOTSan Antonio District- TxDOT San Antonio, TXSan Antonio, [email protected] [email protected]@swri.org(210) 731-5247(210) 731-5247