Raleigh - With congestion along North Carolina's freeways growing, especially during morning and evening commute times, the N.C. Department of Transportation is using a technology new to North Carolina called on-ramp signals to help improve traffic flow for drivers along a stretch of Interstate 540 in north Raleigh.
On-ramp signals, also known as ramp meters, are stop-and-go lights on freeway entrance ramps that work similar to traffic signals. When the signals are activated, vehicles on the ramp must stop when the light is red and wait a few seconds until it turns green before proceeding on to the freeway. This allows only one or two vehicles to merge at a time, which reduces competition for space when merging onto I-540.
"While this is the first time we are using this technology in North Carolina, on-ramp signals are used effectively in several other states and extensively throughout Europe," said Kevin Lacy, state traffic engineer. "The signal spaces out the number of cars trying to merge on the freeway at once, which makes merging smoother. That translates to better traffic flow and more reliable times on the freeway, as well as improved safety and fewer crashes."
The first on-ramp signals in North Carolina will be installed along westbound I-540 at four ramps in north Raleigh:
Falls of Neuse Road (Exit 14)
Six Forks Road (Exit 11)
Creedmoor Road (Exit 9)
Leesville Road (Exit 7)
These areas were selected as pilot sites based on in-depth studies completed in 2013. The project received a high enough score to be funded in the state's current 10-year transportation construction plan.
On-ramp signals are generally used during peak travel times, such as the morning and evening commutes, but can be activated at any time in response to unusual circumstances affecting traffic flow, such as special events, wrecks or construction.
The department expects to award a contract for the project this fall and for the signals to be operational by spring 2017. To kick off its educational outreach for the project, the agency is meeting with local officials from the Raleigh area and will hold a public meeting on Thursday, Sept. 29. The meeting will take place from 4 - 7 p.m. at Abbotts Creek Community Center, 9950 Durant Road, in Raleigh.
Commonly asked questions about on-ramp signals:
What's the difference between an on-ramp signal and a ramp meter? An on-ramp signal and a ramp meter are the same thing. North Carolina uses the term on-ramp signal to describe the technology, but federal guidelines require that advanced-warning signs use the term ramp meter.
Do I have to obey the on-ramp signal? Yes, violating an on-ramp signal can result in being ticketed by a law enforcement officer.
How can vehicles merge safely into traffic from a full stop at a signal? Each signaled ramp is long enough for a vehicle to accelerate to a safe speed before merging into freeway traffic.
How do you keep traffic from backing up onto other streets? On-ramp signals respond to real-time traffic conditions to balance traffic flow. If vehicles start to back up on the ramp, a sensor will activate the signal to adjust and quickly clear the backup. Traffic cameras will also feed live images to the department's traffic operations center, allowing traffic specialists to manually adjust the signals, if necessary.
Additional information is available on the project webpage.