Lesson
Deploy ITS systems strategically to achieve benefits.
San Antonio’s experience with integration of freeway and arterial management systems.
6/1/2001
San Antonio,Texas,United States
Background (Show)
Lesson Learned
- Under periods of significant diversion, San Antonio’s incident response signal timing system offers substantial benefits. However, when diversion is low, implementation simply leads to unnecessary cross-street delays. The application of the incident management plans to minor and moderate incidents can lead to significant reductions in efficiency. This scenario may actually increase delay, even with other elements of the system operating.
- Monitor arterial operations carefully to avoid this situation. First, use of the incident response signal plans was restricted to more severe incidents, such as those involving the blockage of multiple freeway lanes for periods of 45 minutes or more. Second, video surveillance was used by the arterial operations personnel to monitor the impacts of the signal timing changes in real time and to turn these plans off and on when appropriate. Finally, San Antonio undertook a commitment to continually update and broaden the breadth of the incident signal plans.
Use the system's variable message signs appropriately:
- Rerouting around minor incidents is often unnecessary and may even lead to increased delay; however, the posting of the situation to a variable message sign may cause some travelers to proceed with just such a suboptimal solution. For example, modeling of the Medical Center Corridor predicts a 2.5 percent reduction in delay for incident management alone. Under the same scenario, the delay reduction drops to just 1.9 percent when messages are displayed to accompany incident management. This scenario supports the hypothesis that the system may not be needed in every case.
- Mitigate the potentially negative impacts of variable message sign usage by either restricting use to incidents severe enough to justify diversion or by carefully selecting message sets for the signs that minimize erroneous routing decisions.
Lesson Categories
Management & Operations > Operations
Technical Integration > Functional
Application Areas
Intelligent Transportation Systems > Freeway Management > Information Dissemination > Dynamic Message Signs
Intelligent Transportation Systems > Traffic Incident Management > Information Dissemination > Dynamic Message Signs
Intelligent Transportation Systems > Arterial Management > Information Dissemination > Dynamic Message Signs
Intelligent Transportation Systems > Traffic Incident Management > Surveillance & Detection > Imaging/Video
Intelligent Transportation Systems > Traffic Incident Management > Surveillance & Detection > Detectors
States
Countries
Systems Engineering
Focus Areas
Major Initiatives > Integrated Corridor Management Systems
Major Initiatives > Nationwide Surface Transportation Weather Observing and Forecasting System - Clarus
Major Initiatives > Emergency Transportation Operations
Other Program Activities > Amber Alert
Other Program Activities > Public Safety
Other Program Activities > Rural ITS Deployment
Goal Areas
Keywords
DMS, CMS, VMS, Changeable Message Signs, Variable Message Signs, CCTV, closed circuit television cameras, road monitoring, camera imaging, sensors, incident detection, vehicle detector, traffic detection, traffic monitoring, congestion monitoring
Lesson Comments
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