University Bus Systems: Network Flow Demand Analysis
By Craig YannesUniversity of ConnecticutOctober 21, 2008
Introduction
University bus systems are an important form of transportation around university campuses
Research has shown that these systems generate more ridership than their counterparts (Daggett and Gutkowski, 2005)
University enrollment has also been expanding
Problem
The sharp increase in demand has put a strain on university resources to provide an effective bus system
Many routing design decisions have been made subjectively
This results in an inefficient system, which leaves demand centers unidentified, underserved or unserved
Solution
Network flow theory, in conjunction with spatial analysis (GIS), can help remove the subjectivity from university bus system design
Focus of this project is the selection of optimal stopping locations considering operational cost while serving the maximum passengers (demand)
Goals
Create a simple and efficient model framework to analyze the coverage of a university bus system
Analyze the effects of stopping service areas (walk distance to stop) on the selection of optimal stopping locations
Objectives
Collect and generate transportation link and transit demand data
Generate and analyze demand data to create centers which will serve as potential bus stops
Create a network flow model representation and use an appropriate solution technique, yielding the optimal demand centers to be served by the bus system at differing service areas
Background
The following have utilized network flow algorithms and theory to solve transit design (routing, scheduling, frequency, etc.) problems: Ceder and Wilson (1986) Chu and Hobeika (1979) Ranjithan, Singh and Van Oudheusden (1987) LeBlanc (1988) Kocur and Hendrickson (1982) Kuah and Perl (1985)
Background
Overall transit design involves two interest groups (passenger and operator)
Depending on the component being designed, the focus shifts between these groups
This proposed research will focus solely on operator costs while attempting to serve the maximum amount of passengers
Background
Furth, Mekuria and SanClemente (2007) created and used GIS applications to analyze the spacing of transit stops based on the street network and parcel data
The study evaluated walking, riding and operating costs when stops were reconfigured from the existing placement
Similar to this research except that no network flow theory was used
Network Representation
The following design was used to create a network representation of the bus system:
Arcs leading to accessible nodes based on current location
Cost on Links is a function of distance and demand
Nodes representing potential stopping locations
Supply Node(Bus Depot)Supply = Number of demand nodes
Destination nodes which are spread throughout the exterior of the network to pull flow in all directions
Demand = 1 for each node
Data
Connecticut Department of Environmental Protection: Connecticut Street Network Shapefile (1:100,000)
2006 UConn personal geodatabase which included street, building and parking lot feature classes
Transportation Network
0 0.50.25Miles
Demand
Calculated using ITE Trip Generation Manual
Produces auto trips based on the building/area purpose and attributes such as area, number of seats and number of units
Although this research focuses on transit trips, the auto trips can be used to determined relative demand between locations
Building and Parking Lot Demand
0 0.50.25Miles
Potential Stopping Locations
32 Locations were selected at points along the roadway near key intersections and large generators
The demand at each one of these stops is equal to the sum of demand of the buildings and parking lots within a particular distance (1/8, 1/4, 1/2 mile) of the stopping location
5 destination locations were also selected such that the flow would be spread around the network evenly
Potential Stopping Locations
0 0.50.25Miles
Link Generation between Stops
Links represent the transportation path between two stops though it does not follow street layout directly
The following rules were used to create the links between the stops: Links must proceed in a forward progression
(must be getting closer to a destination) Links cannot pass through stops Stops on the exterior must connect with sink
locations
Link Generation
Link Cost
Combination of two factors Distance between stops Demand at the ending stop
Because higher demand should incur less cost the inverse demand was used
This requires a scaling factor so that demand values are comparable in magnitude to distance
1000*Demand
1 Distance CostLink
jijij
Network Representation
Solution Technique
A geometric network was created in GIS weighted with the calculated link cost
The Network analyst toolset in ArcGIS was used to find the shortest path between the source node and each of the 5 sink nodes
The nodes that lie on these shortest paths are the optimal stopping locations
1/8 Mile Service Area
1/4 Mile Service Area
1/2 Mile Service Area
Results
Path
1/8 mile 1/4 mile 1/2 mile
StopsDistance(miles) Stops
Distance(miles) Stops
Distance(miles)
1 3-5 2.54 3-5 2.54 3-5 2.54
2 13-12-11-8 1.14 13-12-11-22 0.99 13-29-10 0.79
3 13-12-11-22 0.99 13-12-11-22 0.99 13-12-11-22 0.99
4 30-23-32-20 1.32 30-23-32-20 1.32 30-23-32-20 1.32
5 30-23-28 0.99 30-23-28 0.99 30-23-28 0.99
Total17 stops
(12 unique)6.98
17 stops(11 unique)
6.8316 stops
(13 unique)6.63
Conclusions
A model framework has been created which analyzes a bus network yielding optimal stopping locations
Increasing the service area, reduces the distance traveled and increases that amount of unique stops served by the system
Planners must be cautious when trying to balance ridership and efficiency
Analyzing the system for different service areas can help quantify this relationship and create a more efficient system
Future Research
Expand the analysis area to include other locations surrounding the campus
Acquire or generate more accurate demand data
Comparison / application to the existing bus system
Incorporate the effect of larger service areas on demand
Create similar network frameworks that focus on the other aspects of bus system design
Comments / Questions?
References Daggett J. and Gutkowski R. (2003). University Transportation Survey: Transportation
in University Communities. Colorado State University. Sutton J. C. GIS Applications in Transit Planning and Operations: A Review of Current
Practice, Effective Applications and Challeneges in the USA. Transportation Planning and Technology, Vol. 28, 2005, pp. 237-250.
Furth P. G., Mekuria M. and SanClemente J. Stop-spacing Analysis Using GIS Tools with Parcel and Street Network Data. Presented at 86th Annual Meeting of the Transportation Research Board, Washington, D.C., 2007.
Ceder A. and Wilson N. H. M.. Bus Network Design. Transportation Research Part B, Vol. 20B, 1986, pp. 331-344.
Chu C. and A. G. Hobeika. In Transportation Research Record: Journal of the Transportation Research Board, No.730, Transportation Research Board of the National Academies, Washington, D.C., 1979, pp. 7-13.
Institute of Transportation Engineers (ITE). Trip Generation, 6th ed., Washington, D.C., 2003. Kocur G. and Hendrickson C. Design of Local Bus Service with Demand Equilibrium.
Transportation Science, Vol. 16, 1982, pp. 149-170. Kuah G. K. and Perl J. A methodology for feeder bus network design. In Transportation
Research Record: Journal of the Transportation Research Board, No.1120, Transportation Research Board of the National Academies, Washington, D.C., 1985, pp. 40–51.
LeBlanc L. J. (1988). Transit system network design. Transportation Research Part B, Vol. 22B, 1988, pp. 383-390.
Ranjithan S., Singh K. N., and Van Oudheusden D. L. The Design of Bus Route Systems – An Interactive Location-Allocation Approach. Transportation, Vol. 14, 1987, pp. 253-270.
References
GIS Data Connecticut Department of Environmental Protection
http://www.ct.gov/dep/cwp/view.asp?a=2698&q=322898
Richard Mrozinski, University of Connecticut Department of Geography
Images Title: http://www.park.uconn.edu/ Problem:
http://www.news.com.au/dailytelegraph/story/0,22049,2 1265300-5011906,00.html
Background: www.caliper.com/UK/transcad.htm Questions:
http://www.pritchettcartoons.com/newcar2.htm http://home.fuse.net/ard/jandress/transfuture3.jpg