It’s All in the Timing

November 24, 2007

The last time you sat in your car at a traffic signal or stood impatiently at the bus stop, did you feel like you were wasting precious time and energy as you waited?

Much of this unpleasant waiting can be attributed to poor traffic signal timing. Nearly 300 million hours of vehicle delays occur each year because of signal timing, according to the Oak Ridge National Laboratory in Oak Ridge, Tennessee. And, according to the Institute of Transportation Engineers (ITE), 75 percent of the country’s 330,000 traffic signals could be improved with updated equipment or adjusted the timing.

Traffic signal retiming is one of the most cost-effective ways to improve traffic movement and make streets safer. It can reduce overall travel time, cut delays, and create fuel savings.

The transportation engineering community knows it can do better, provided the proper resources. ITE recently conducted a nationwide self-assessment, dubbed the National Report Card, where the national average was a disappointing D minus.

Part of the problem is that the investment in our transportation system has not kept pace with demand during the past two decades. We continue to use 20-year-old technology and infrastructure that, while effective, doesn’t incorporate recent advances in communications and equipment that could improve the system’s performance. Such improvements include updated traffic signal timing plans, new strategies for improving transportation, and better customer service.

Many agencies’ transportation budgets and resources for proactive management and maintenance were cut during the economic recession. However, despite these fiscal constraints, there have been some great advances related to traffic signal operations.

Such advances include the development of a transit signal priority, which provides preferential treatment to buses as they approach traffic signals. This new technology elongates green lights for buses, allowing them to provide better service by staying on schedule.

Signal timing adjustments can help manage traffic during construction. While such adjustments are slight and alter a signal’s timing by mere seconds, they improve access for motorists and buses alike.

Other advances include flashing yellow arrows for left turns at signals. The flashing yellow arrow means a driver can turn left after waiting for an acceptable gap in oncoming traffic. The flashing yellow arrow allows more flexible operation of the signal such as giving an agency the ability to change the signal operation by time of day.

Another example is engineers’ ability to operate signal systems in real time. Establishing communication with signals from traffic management centers can improve an agency’s responsiveness in changing traffic patterns and addressing user complaints. This includes investment in analysis tools that aid engineers in evaluating performance, documenting decisions, and comparing alternatives.

Through the development of these new strategies, the transportation engineering community is answering the call to do better. The profession is moving forward with fresh solutions that address not only the economic bottom line, but the environmental and social aspects as well.

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