Variable Speed Limit System activated on Schuylkill Expressway between King of Prussia and Philadelphia

Today at the Park & Ride lot in West Conshohocken, PennDOT Secretary Yassmin Gramian held a press event to announce the completion of the installation of Variable Speed Limit (VSL) and Queue Detection and Warning (QDW) systems along 14 miles of the Schuylkill Expressway (I-76) between King of Prussia and Philadelphia. The corridor serves more than 130,000 vehicles each day.

“These devices will help reduce congestion and greatly improve safety by warning drivers of changing conditions based on real-time expressway, traffic and weather events,” PennDOT Secretary Yassmin Gramian said. “This is one of the ways we are using operational strategies and technologies to actively manage travel and traffic flow along this critical corridor.”

PennDOT has now activated 72 VSL signs and an end-to-end QDW system along eastbound and westbound Schuylkill Expressway (I-76) from the Pennsylvania Turnpike in Montgomery County to the U.S. 1 North (Roosevelt Expressway) Interchange in Philadelphia. The activation will begin a technology testing period expected to continue through May 10.

From the announcement:

When the VSL signs are first activated, drivers can expect to see a fixed speed limit posted on VSL signs matching the speed limits posted on existing static speed limit signs. These speed limits will be set at 55 mph in Montgomery County and 50 mph in the City of Philadelphia. Drivers will also see real-time display of electronic warning messages on roadside signs, including alerts about upcoming slowdowns, lane closures, or other adverse conditions. 

Beginning Monday, May 10, existing static speed limit signs will be removed, and posted speed limits will begin to change along the corridor. Initially, the VSL signs will vary between 35 mph and 55 mph based on real-time traffic and safety conditions (50 mph maximum in City of Philadelphia). This range of speed limits may be slightly adjusted after the performance of the system and traffic progression results are collected and analyzed.

“During the time the VSLs are static, the system will be further tested by staff in our Regional Transportation Management Center in King of Prussia,” said PennDOT Assistant District Executive for Operations Lou Belmonte. “This testing period will run through May 10th to allow motorists to get accustomed to the active systems along the corridor.”

“Speed limits posted to the new VSL signs on I-76 will serve as enforceable, regulatory speed limits, not recommended speed advisories,” Pennsylvania State Police Captain Robert Krol said. “All motorists should follow the posted speed limit on the VSLs.”

Starting Monday, May 10th, drivers will notice speed limit signs will change based on real-time travel conditions. This is an indication of congestion occurring ahead and an effort to improve the flow of traffic and reduce stop-and-go conditions and the potential for rear-end crashes.

According to PennDOT data, there were 2,580 reportable crashes on I-76 in Montgomery County from 2015 through 2019. Of those, 1,741 were rear-end crashes. VSL deployments in other states have been shown to reduce crashes by as much as 30 percent.

The activation of the VSL and QDW systems is the first phase of a long-range, comprehensive, multimodal transportation management plan designed to enhance travel and safety along the Schuylkill Expressway (I-76) corridor between King of Prussia and Philadelphia.

The next phase, currently in design, will include additional active traffic management strategies such as the modernization of traffic signal systems along several roadways running near the expressway, and transforming the existing shoulders on portions of the Schuylkill Expressway (I-76) to accommodate an additional travel lane or “flexible” travel lane during peak travel times.