ATHENS, Tenn. — Motorists in many cities may notice that traffic signal lights are becoming brighter as cities swap out incandescent bulbs for LEDs.

Cities that install light-emitting diode bulbs notice they save money on electricity and replacement costs.

Athens has switched nearly two-thirds of its signals to LED, Public Works Director Shawn Lindsey said. The city’s utility bill is $300 a month lower, and the lights are projected to last for 10 years instead of the one to three years that incandescents last.

“So far we have never replaced an LED bulb in Athens, and we have some that are about 5 years old,” Mr. Lindsey said.

According to a 2005 city study, “this capital expenditure will pay for itself through the savings in power usage alone in about eight years,” he said.

Instead of changing out whole traffic lights, the city worked with colors. It started by replacing all the red lights with LED bulb, then moved to green lights and now is replacing yellow and flashing lights.

“We should be completed with our LED change-out, with the exception of College and White Street/Jackson, by spring,” Mr. Lindsey said. “If funds are available we plan to replace all the signal lights at College and White Street in our next fiscal year’s budget.”

Other Southeast Tennessee cities such as Dayton and Etowah also are installing LED signals, officials said.

A Cleveland, Tenn., study of replacing its 67 signals found at an average of about $2,500 per intersection just for lights for each intersection, city official Ed Griffith said.

He said new lights are LEDs but working incandescents will be left alone until replacement money is available.

“It’s a big expense, and we are planning on putting money in next year’s budget,” he said.

Decatur, the Meigs County seat, used a $15,000 Appalachian Regional Commission grant to install LED signal bulbs and replace some damaged housings.

“We had some lights broken and the glasses cracked and we were really getting worried” about drivers being able to see the old lights, city spokeswoman Laura Smith said. Drivers seem to like the new lights, she added.

Knoxville firm Aldis Inc. installed and maintains Decatur’s LED systems.

Vice President of Sales Eric Seabrook expects LEDs to continue becoming more cost-effective in the next few years.

“I do not foresee anything in the future to replace the LED light technology,” he said.