Developments in high resolution traffic sensors over the past decades are providing a wealth of empirical speed-flow data. Travel demand models use speed-flow relationships to assign traffic flows to network links. However, speed-flow relationships have not been revalidated against new detailed traffic sensor data. Therefore, it is necessary to revisit speed-flow relationships based on actual measured conditions on network links rather than assuming constant speed-flow relationships over entire highway network systems.
Speed-flow relationships have been particularly difficult to calibrate and estimate when traffic volumes approach capacity, i.e. when the v/c ratio approaches one. This thesis empirically evaluates the speed-flow relationships for v/c < 1 using field data. For congested conditions (v/c > 1) a theoretical approach is taken. A new methodology to determine the distribution of the activation of bottlenecks, bottleneck duration, and bottleneck deactivation is proposed. This thesis is a new contribution to understand the stochastic nature of freeway capacity as well as bottleneck duration, activation, and deactivation. Unlike previous research efforts, this thesis studies speed-flow relationships at the lane level and later presents a method to estimate speed-flow relationships at the link level.
|Advisor:||Figliozzi, Miguel A.|
|Commitee:||Gliebe, John, Monsere, Christopher M.|
|School:||Portland State University|
|Department:||Civil and Environmental Engineering|
|School Location:||United States -- Oregon|
|Source:||MAI 49/02M, Masters Abstracts International|
|Subjects:||Civil engineering, Transportation planning, Urban planning|
|Keywords:||Flow, Freeway, Planning, Probabilistic, Speed, Travel time|
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