Adaptive Signal Control (ASC) can be an effective tool to improve operations and traffic signal timings. ASC allows a signal system to respond in minutes or even seconds to traffic volume and capacity changes. This is accomplished by automating data collection and analysis and implementing system-wide changes. However, ASC programs are far from simple. How can we decide when, where, and how to implement ASC successfully? Here are three things to consider.
Selecting the right corridor.
ASC is not an effective solution for every corridor. ASC does not create capacity; rather, it optimizes green times using a variety of mechanisms. It’s therefore most successful in systems near capacity with available green time to reallocate, as well as high traffic volumes to warrant the investment. Corridors with high variability and unpredictable traffic demand volumes, or large fluctuations in demand are also ideal candidates. ASC may not be effective on well-timed, congested, and oversaturated corridors, corridors with insufficient or unreliable detection, or on corridors with heavy pedestrian volumes.
Selecting the right ASC technology.
There are different types of ASC technologies, which have differing capabilities. Which one to pick depends on the goals of the specific corridor it will be enhancing and how it fits into your current systems. To implement ASC technology, we’d need to look at the interoperability between programs, as well as compatibility with existing field equipment.
Consider the cost.
Keep in mind, ASC requires additional traffic engineering and signal maintenance capabilities, experience, and time, all of which can vary with system complexity. The resources needed for installation and upkeep should also be considered. While an adaptive control system should reduce time spent on periodic optimization of signal timing plans and improve operations during those times of variable traffic volume, these systems are not “set it and forget it.” A champion should be chosen to look after the installation, operation, and management of the adaptive system. Otherwise, many adaptive signal control systems have been neglected and ultimately turned off because the system was not performing as desired. Besides the internal agency costs, budget for annual vendor maintenance costs for warranty, system updates, and periodic troubleshooting support.
Overall, ASC can be an effective tool to reduce congestion and improve traffic flow in certain corridors. By choosing the right corridors and the right ASC programs, we as transportation professionals can successfully implement this technology to better our cities.
