Evaluation of the Anaheim Advanced Traffic Control System Field Operational Test: Executive Summary

Problem

The city of Anaheim, California, experiences heavy traffic on a regular basis. Delays at intersections are a significant problem, and many special events create special traffic problems. The city has an advanced traffic control system, but wanted to test out several new technologies, so this field operational test was set up both to assess the technical performance of these methods and to analyze the institutional issues around their implementation and operation.

The three systems were: SCOOT (Split, Cycle, and Offset Optimizer Technique), a second generation technology for controlling systems of signals as opposed to isolated intersections, already in use in Europe; a 1.5 Generation Control system under development, whose purpose was to update baseline timing plans for the entire system; and a video traffic detection system presented as a low-cost alternative to loop detectors for critical areas

Method

The evaluation was broken down into three main parts: a performance assessment of the technologies, an assessment of the institutional issues, and a separate evaluation of the video traffic detection system.

For the performance assessment, we looked first at how well SCOOT "sees" traffic and then at how well it performs to control traffic.

Findings

SCOOT is designed to rely on information from loop detectors placed farther away from the intersections than the mid-block locations of the loops already in place in Anaheim. We needed to know whether these loops could provide adequate information to the system, so we compared SCOOT's estimates of queue length and clearance time to real time video at certain intersections, and identified large inconsistencies. Nevertheless, SCOOT successfully models traffic conditions, in general, but can be improved either by changing the location of loop detectors or by adjusting global control settings to compensate for the actual location of detectors.

To assess SCOOT's performance, we used teams both at intersections to measure delay and in cars to measure travel time, before and after implementation. We discovered that SCOOT performed better than the existing system during off-peak hours, and very well at certain intersections during special events. However, our findings are inconclusive as to whether SCOOT is better than the system already in place.

To evaluate institutional issues, we used direct observation and interviews, all of which produced subjective information that was structured to provide many different points of view. We looked at implementation, operations, transferability, and maintainability of the system. There was an immediate problem with delaying implementation due to a vacancy in a key position (Principal Traffic Engineer), which led to a lack of experience and authority in the city's relations to the contractor (Siemens). We were not able to adequately evaluate operational issues because of the resulting delays, which led to late delivery, and limited staff training and experience prior to the evaluation. In terms of transferability of technology, we concluded that products that are not widely deployed are essentially still in the research and development process, subject to delays, changes, and cost overruns. This is especially true for the 1.5 GC system. Maintaining the new systems would involve significant costs, and much more training is needed to properly utilize it. Our overall conclusions in regard to institutional issues is that we have no specific recommendation, but costs would be likely to go up if SCOOT were to be expanded beyond its present limited deployment.

The last evaluation task, of the video system which is marketed as a low-cost alternative to loop detectors, found that its user interface is unsophisticated but effective. The system's performance results were good under ideal lighting and light traffic conditions, but not so good in low light, night, rain, or heavy traffic. (The manufacturer, Odetics, says it has since addressed and corrected these issues, but we have not evaluated the new system).