| The Pennsylvania Department of Transportation today announced that it will reactivate ramp meters on four entrance ramps to Interstate 476 in Delaware County beginning 3 p.m. Tuesday afternoon, November 16.
Ramp meters – traffic signals without the amber caution light – will soon begin operating at the following ramps:
• MacDade Boulevard on-ramp to I-476 North in Ridley Township
• Baltimore Pike on-ramp to I-476 North in Nether Providence Township
• Baltimore Pike on-ramp to I-476 South in Nether Providence Township
• U.S. Route 1 on-ramp to I-476 South in Marple Township
PennDOT District Executive Andrew L. Warren said ramp meters are being reactivated because they are now interconnected and controlled by a central software system that allows PennDOT to remotely control the meters from its Traffic Control Center in King of Prussia.
To complement the system, overhead closed circuit television cameras are in place to enable PennDOT to view the affected interchanges and adjust the meters depending on traffic volumes.
“The central computer system is now in place to make the ramp meters operate the way they were designed to operate,” Warren said. “Initially, we will meter four ramps during rush hours to enhance travel along the four-lane section of I-476. We do have the capability to activate meters on additional I-476 ramps when traffic volumes rise to a level that warrants their use.”
The ramp meters will operate weekdays from 6:30 a.m. to 9 a.m. and from 3 p.m. to 7 p.m.
PennDOT operated ramp meters manually on selected ramps along I-476 in Delaware County from 1999 through late 2001; however, ramp meters at that time acted on a time-of-day program, using a fixed metering rate regardless of traffic volumes on I-476 or on the affected ramps. Due to the lack of a central software system, PennDOT did not have the ability to remotely detect system shutdowns or alter the timing of the meters.
Prior to activating ramp meters at selected ramps in 1999, PennDOT performed travel time studies to measure peak-hour travel speeds on I-476. The study found that mainline speeds dropped from 55 miles per hour (mph) to 25 mph at interchange merge areas on I-476 between State Route 3 and I-95 in Delaware County. It also found that mainline speeds rose to 55 mph about two miles away from each interchange.
Warren said traffic flow on I-476 showed a modest improvement when ramps meters were used a few years ago. “We saw a few miles per hour improvement in mainline travel speeds on I-476 when ramp meters were used in the late 1990s and early 2000s.
“Ramp meters are a tool to help achieve more consistent travel speeds on I-476 by allowing one car to merge at a time rather than having a platoon of vehicles merge and force their way onto the highway,” Warren said. “A steady stream of merging vehicles slows mainline travel speeds and creates what is known in traffic engineering as a ‘shockwave’ effect.”
A ramp meter flashes a red and green light to control the rate at which cars and trucks enter the flow of traffic. By pacing the entry of vehicles onto I-476, merging vehicle are less likely to slow down mainline traffic, thereby improving travel times and reducing the potential for crashes at entrance ramps.
The ramp meter works much like a traffic signal. When the light is red, you stop. When the light turns green, you go. But unlike traffic signals, only one car or truck per lane is allowed to enter I-476 on a green light. The ramp meter will shine green for 2 to 4 seconds and red for 2 to 13 seconds. The meter’s time cycle will depend on I-476 traffic volumes.
When a driver approaches a metered ramp, he or she needs to remember the following tips:
1. Wait your turn in line
2. Drive slowly up to the stop line marked on the ramp
3. Stop when the signal is red
4. Wait for the light to turn green
5. Proceed onto I-476 and merge safely into traffic
Warren said drivers will know when a ramp is being metered by the flashing warning light posted on each entrance ramp. He also said that PennDOT will post a variable message board on these four ramps to inform motorists of the date when ramp metering begins.
Motorists are reminded that disregarding a ramp meter is a punishable offense and carries the same penalties as running a red light.
The ramp meters are part of PennDOT’s Traffic and Incident Management System (TIMS) that strives to move traffic more efficiently on major expressways. PennDOT’s TIMS system in southeastern Pennsylvania includes an integrated combination of 97 closed circuit television cameras, 40 variable message boards, 120 traffic detectors, and an Expressway Safety Service Patrol to monitor traffic, ease congestion and detect incidents for improved emergency response time.
The $1.8 million ramp metering system on I-476 was part of PennDOT’s $6.8 million project to install a TIMS system on the highway in the 1990s. In addition to ramp meters, this system included closed circuit television cameras, traffic detectors, fire hose standpipes, and incident management signs.
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