System implemented in 2022 changes limit in response to current traffic conditions
Technology recently installed on a 14-mile section of I-76 (Schuylkill Expressway) between King of Prussia and Philadelphia is improving safety and traffic flow on the roadway, according to the Pennsylvania Department of Transportation.
PennDOT data shows that crashes, injuries, and travel time have decreased on the corridor since the department installed 72 Variable Speed Limit (VSL) signs and additional electronic message signs supporting a new Queue Warning (QW) system in June 2021.
VSL signs display speed limits that are adjusted based on real-time traffic, roadway, and weather conditions. The QW system uses traffic data to update the electronic message signs in real time, alerting motorists about congestion before they reach it so they can slow down and watch for slowed or stopped traffic.
PennDOT encourages all motorists traveling on I-76 (Schuylkill Expressway) to pay attention to the speed limits (between 35 mph and 55 mph in most areas) and queue warning messages that are posted 24 hours a day. In general, a motorist encountering a reduced speed limit should expect to reach slower moving or more congested traffic within a mile to a mile-and-a-half of that reduced speed limit sign. Following the posted speed limit is safer and improves traffic flow. The speed posted on a VSL is the legal speed limit when it is displayed.The real-time, responsive technology reduces speed limits as needed, improving motorist safety. Compared to the five-year average from 2015-2019 data (2020 and 2021 data was excluded due to reduced traffic during the pandemic), the average of 2022 and 2023 data shows:
Average annual crashes have decreased 22 percent from 568 crashes per year to 444 crashes per year.
Average annual rear-end crashes have decreased 32 percent from 380 to 257 per year.
Average annual injuries have decreased 20 percent from 413 injuries per year to 330 injuries per year (2022 & 2023).
Average annual serious injuries have decreased 62 percent from 6.6 per year to 2.5 per year.
PennDOT traffic data shows daily traffic volumes on I-76 (Schuylkill Expressway) had recovered from pandemic lows by 2021, with the corridor now carrying 10 percent more traffic than it did in 2019.
The overall reduction in crashes is helping to improve traffic flow by keeping more lanes open on a more consistent basis. In 2023, travel time decreased four minutes during the eastbound evening peak travel time (4 p.m. to 7 p.m. and two minutes during the westbound morning peak travel time 5 a.m. to 9 a.m. compared to 2019. PennDOT estimates that these results are having a positive economic impact on the community due to fewer crashes and hours of delay in the amount of $46.8 million per year.
