AASHTO Journal - Alabama DOT Details Safety Role of ‘Signal Crews’

The Alabama Department of Transportation (ALDOT) recently provided a behind-the-scenes look at the crucial role played by its “signal crews” in ensuring the smooth operation of traffic signals for state roadways.

[Above photo by ALDOT]

In a blog post, ALDOT noted that signal crews provide even more critical emergency response and repair service following severe weather, power outages, and other disruptions.

“When the lights go dark, that intersection becomes dangerous fast,” explained Kevin Purdue, electronic signal shop supervisor at ALDOT’s Central Office. “We’re not just fixing equipment. We’re protecting people. If we don’t do our job right, people will get hurt.”

A standard traffic signal with three stacked lights stands nearly four feet tall, ALDOT noted, including its black backplate. Each circular lens is 12 inches wide, roughly the size of a dinner plate and the full assembly can weigh up to 50 pounds.

Crews mount signals on mast arms or span wire that can extend 60 feet or more, depending on the roadway – carefully calibrating its timing to match posted speed limits and intersection spacing to support safe traffic flow and reduce unnecessary stops.

[Editor’s note: Other state departments deploy such specialized “signal crews” as well for the same reasons, such as this traffic signal upgrade endeavor undertaken by an Idaho Transportation Department team.]

Most signals are equipped with vehicle detection systems, ALDOT added, such as sensors and cameras to help identify when a vehicle is present and triggers the light cycle accordingly. These systems play a crucial role in maintaining traffic flow and ensuring intersections are safe, Purdue noted.

“Traffic signals are timed based on the posted speed limit,” he said. “If drivers go too fast or too slow, they fall out of sync with the signals. Following the speed limit keeps traffic flowing as designed and is also the safest option.”

ALDOT’s signal crews are also key to upgrading traffic signal technology as well. For example, earlier in 2025, ALDOT’s Southwest Region completed a major traffic signal modernization project through the Regional Traffic Operations Program or RTOP.

That upgrade included new controllers and hardware at more than 150 signals, improving reliability and giving engineers greater tools to manage traffic in real time; enabling engineers to monitor and coordinate signals from a joint operations center, supporting faster response and better traffic flow across the region.