טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentRavit Fux
SubjectIntegration of Road Network Reliability into the Traffic
Assignment Problem
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Full Professor Bekhor Shlomo
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

The traffic assignment problem is a process of distribution of traffic demand onto a transportation network. The solution of the assignment problem is a set of traffic volumes on the network' links. The traffic assignment model is used in many planning aspects such as traffic engineering, urban planning, economic evaluations and more. Therefore, reliable results of traffic assignments are essential.


The assignment solution is based on behavioral assumptions about the drivers. The common basic assumption is that each driver selects the route with the lowest journey costs. In the stochastic user equilibrium model, drivers do not have perfect knowledge of travel costs, and route choice is based on their perceived shortest travel time.


Reliability is a very wide concept, which can be found in many scientific disciplines.

Generally, reliability is defined as the stability level of the service, which is normally offered by a system or a product, under different conditions. Many factors can compromise the reliability of the results of the traffic assignment. In this thesis, the reliability of network links is considered, in an attempt to model the condition of the road and its close environment.


The thesis reviews several methods related to reliability and traffic assignment models. The main body of research deals with integration of road network reliability into the traffic assignment. This is accomplished through a modification of the Method of Successive Averages algorithm. The reliability factor in the program is expressed in terms of road reliability.


The model is tested using several transportation networks: one imaginary small network, and two other well-known networks in the literature. Results show that when reliability values of the links are set to be high, the resulting traffic pattern is similar to deterministic assignment, which is expected from the theory.


The model developed in this thesis allows the planner or the user to obtain more realistic results related to travel time reliability. In the ideal situation of the perfect information, the model assigns a high value for the link reliability parameter, and the corresponding results are close to the deterministic user equilibrium.


This thesis presents a simple tool that allows the possibility of observing the influence of reducing the links' reliability on the overall traffic pattern. This is a tool that can be used for finding a traffic assignment solution that might be more realistic, and since the assignment products serve in many planning aspects, that might be very useful.