Critical assessment of the features of two ramp metering optimization models /
| Main Author: | |
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1993.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | In this dissertation, two ramp control models used for freeway traffic management, FREQ and S971, are critically reviewed. FREQ was developed at the University of California, Berkeley and S971 is being developed at the Texas Transportation Institute, Texas A&M University. Assessments were conducted using a macroscopic simulation program, FREFLO, which is supported by the Federal Highway Administration. Other tools, including LINDO and SAS, were used to assess the models. Based on the assessment results, new features for S971 were developed to adapt the model to the constrained operational conditions that may exist in a freeway corridor during congested traffic conditions. The study results showed that S971 is preferable for Texas freeways to the FREQ model in view of its theoretical basis of modeling and its simulated traffic performance. A user-friendly software version and program manual, as available with the FREQ model, are needed to encourage wide acceptance of the S971 model. In developing the procedure for selecting the pm (i.e., the fraction of traffic in the merge lane) factor used in the S971 model, a new concept for freeway lane equilibrium in the merging area was introduced into freeway ramp control for corridors in constrained operational conditions. This concept states that the system tends to equilibrate and adjust itself toward system optimum. An equation derived for estimating the equilibrium p[m] was recommended as the best selection and an algorithm for the S971 model was designed as a part of a real-time freeway control system. To provide the S971 model with adaptability to non-steady state freeway conditions, a self-calibration algorithm for the S971 model was developed for queueing conditions that may exist in a freeway corridor. By taking advantage of information available on freeway link volumes, the proportion of vehicles in each freeway section entering from the on-ramps is adjusted for queueing conditions from which freeway link volumes can be better estimated. The capability of the algorithm was illustrated and tested within a limited scope of study. |
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| Item Description: | Vita. "Major subject: Civil Engineering." |
| Physical Description: | xiv, 249 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references. |