6. Conclusions
The initial conclusion that may be drawn as a result of this effort is that there has been much progress during the last several decades in the area of traffic signal timing optimization. This has resulted in providing the Traffic Engineer with several very powerful alternatives to use to optimize signal settings. Because of this progress, it was concluded that the proposed research efforts should concentrate on areas other than optimization.
As noted in the previous section, 12 projects were identified that offered the potential to improve the traffic signal timing process. Obviously, some of these projects offer more promise than others. The three projects in priority order that offer the most potential are note below with a brief discussion of the selection.
6.1 Extended Signal Timing Manual (Project 8)
When we evaluated the literature with respect to the overall signal timing process, we were surprised when we found that there was no nationally accepted document that described that entire signal timing process. Several states produce a signal timing manual that defines the suggested approach for that state.
We feel that this project is a high priority since many Cities and States could benefit from a well-written, well-illustrated, Signal Timing Manual. We feel that the Manual should contain not only the signal timing procedures, but also the evaluation procedures that we described in Project 9 – Signal Timing Field Adjustment Techniques. This combination would place the relevant information concerning the signal timing process in one document.
6.2 Short Count Procedures (Project 1)
We selected this project as another high priority, second only to the development of the Signal Timing Manual. Virtually all discussions regarding signal timing eventually evolve into a discussion of the costs related to collecting turning movement data. One obvious way to minimize this cost is to minimize the time required to obtain this data. This is the purpose of this project.
The objective of this project is to develop and prove the optimum technique to obtain estimates of peak period traffic flows using short-term observations. The specific techniques would be based on procedures that can be followed by a single person to obtain accurate estimates of all intersection movements. A critical issue is to determine how many approaches a single person can observe simultaneously. Obviously, at low volume intersections, a single observer can count all traffic movements. At high volume intersections, this is not possible. The developed procedure, therefore, must allow for a single observer to count one or more traffic movements in sequence.
6.3 Estimate Turning Movements from Detectors (Project 3)
This project is closely related to the Short Count Project since it also addresses the issue of data collection. All current signal systems have the ability to capture detector data, and many systems have the ability to export these data to optimization programs and import the resulting timing data. However, there is not defined process (supported by research) that describes the detector-to-signal parameter transformation.
A research conducted by Martin developed and evaluated a model, Turning Movement Estimation in Real Time (TMERT), that infers unknown traffic flows (intersection turning movements) from measured volumes in sparsely detectorized networks. The model has shown its ability to accurately estimate turning movements. This project would expand on the work conducted by Martin et. al. and determine if the process can be simplified from a complex Linear Programming research model, to a practical application that can be interfaced to systems typically deployed in the United States.
