Traffic

Here’s how those I-540 ramp meters work and how to navigate them

Introducing On-ramp Signals in North Carolina

To enhance the overall flow of traffic during peak times and to improve safety, NCDOT is looking to a proven strategy called on-ramp signals also known as ramp meters.
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To enhance the overall flow of traffic during peak times and to improve safety, NCDOT is looking to a proven strategy called on-ramp signals also known as ramp meters.

After a software glitch Tuesday, N.C. Department of Transportation officials say the new ramp signals at four Interstate 540 on-ramps in North Raleigh were working as intended Wednesday and that traffic on the highway was noticeably smoother as a result.

That may not be comforting to some commuters, who reported traffic backups on the roads leading to the ramps. The Nextdoor social network for neighborhoods around the Leesville Road interchange included several comments from people complaining about the traffic there Wednesday morning.

“I have commuted to RTP on 540 for 10 years,” one post began. “The drive this morning took 40 minutes instead of the usual 15 minutes solely because of the back up on Leesville. Once you get on 540 it does flow smoothly. But the crawl from my neighborhood to the 540 ramp was 10 times heavier with traffic than usual.”

NCDOT installed the lights on the westbound I-540 on-ramps at Leesville, Creedmoor, Six Forks and Falls of Neuse roads. Sensors in the pavement detect when traffic on the ramps gets heavy, turning on lights that alternate between green and red to let one or two cars onto the freeway at a time. The idea is that putting some space between the vehicles leaving the ramp should make it easier for them to merge into traffic on the highway, improving the flow and reducing the number of accidents.

The system was turned on Tuesday morning, and the lights began flashing at about 6:50 a.m., said NCDOT spokesman Steve Abbott. Within minutes, workers at NCDOT’s traffic operations center who monitor the system with cameras noticed that the lights were out of sync, and the system was turned off at 7:15 a.m., Abbott said.

After a wiring problem was fixed, the system was tested later Tuesday morning and worked fine, he said.

The sensors in the pavement are designed to determine if traffic from the on-ramp is backing up onto the road and turn the light green long enough to clear the backup. The traffic operations center can manually adjust the signals if necessary as well. Abbott said that wasn’t necessary on Wednesday.

NCDOT installed the lights on the westbound I-540 on-ramps at Leesville, Creedmoor, Six Forks and Falls of Neuse roads. Sensors in the pavement detect when traffic on the ramps gets heavy, turning on lights that alternate between green and red.

The traffic on the ramps will move more smoothly as drivers get used to the new lights, Abbott said. Many drivers are still in the habit of merging into a single lane on the ramp, rather than staying in two lanes down to the ramp signals.

“The more cars you put on the ramp, the less cars are going to be backed up,” he said. “It’s a learning process. It will take time.”

These are the first ramp signals in North Carolina. NCDOT says if they work well on I-540, they will be installed elsewhere in the state.

Richard Stradling: 919-829-4739, @RStradling

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