After a month of testing, PennDOT’s speed limit and queue detection warning system is now fully effective on the Schuylkill highway from Philadelphia to King of Prussia.

Drivers who extend 14 miles along this 76-mile interstate will see electronic signs with variable speed limits. Determined based on real-time travel conditions. They indicate that congestion has arrived and the speed should be adjusted to coordinate the flow of traffic.

PennDOT officials said that all existing static speed limit signs have been removed from the corridor. The 72 electronic signs installed last month now display speed limits ranging from 35 mph to 55 mph, with a maximum speed of 50 mph in Philadelphia.

After collecting and analyzing the system performance and traffic progress results, the speed limit range can be adjusted slightly.

The speed limit posted on the electronic sign is a legally enforceable speed limit, and the use of speed recommendations is not recommended.

The new roadside signs will also include real-time display of electronic warning messages, including alerts for upcoming decelerations, lane closures or other adverse conditions.

The sections affected by the new VSL system serve more than 130,000 vehicles every day and are notorious for traffic jams. After analyzing the traffic and crash patterns of the past few years, PennDOT has invested in technological upgrades and found that about two-thirds of the accidents along the corridor are rear-end collisions.The agency quoted statistics showing that The VSL system can reduce crashes by up to 30%.

In the United States, the VSL system was first introduced at Lodge Freeway in Michigan in 1960. Their use in the United States has expanded to at least 15 states. They have been deployed more widely in Europe, with successful results in the UK, Germany and Denmark.

PennDOT said its VSL and queue detection warning system is the first phase of a long-distance multimodal transportation management plan that aims to improve the travel and safety of I-76 between Philadelphia and the King of Prussia.

The later stages will include the modernization of the road traffic signal system along the expressway and the change of some road shoulders during peak hours to accommodate additional driving lanes.