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VSL Pilot Program Reducing Speeds, Crashes in District 2

September 07, 2022 12:00 PM
By: Marla Fannin


​Severe winter weather conditions significantly reduce driver visibility. This reduced visibility coupled with drivers' tendencies to drive too fast for conditions greatly increases their chances of being involved in a crash. Implementing low cost, innovative infrastructure improvements to combat these issues are crucial to PennDOT's mission to reduce highway fatalities to zero by 2050, which is why District 2 recently implemented a pilot program that allows us to alert motorists of reduced speed limits on the interstate by way of Variable Speed Limit sign deployments. 

The LED display on the unit alerts motorists to the normal posted speed limit in their deployment area under normal circumstances. In the event of severe winter weather, operators in the District's Regional Traffic Management Center can change the displays on the units remotely from their workstations and immediately alert drivers to a speed limit reduction. The units are equipped with flashers above and below the LED display and will be set to flash to draw extra attention in the event of a reduction. 

During the pilot program, District 2 deployed 14 VSL units along its Interstate 80 corridor in Clearfield County. The signs were placed eastbound and westbound between mile markers 101 at the DuBois interchange and mile marker 123 at the Woodland interchange from February 2 through the end of the pilot study on March 12. During that timeframe, the District's Regional Traffic Management Center requested and was granted permission by the State Traffic Management Center to reduce the speed limit on I-80 from 70 miles per hour to 55 miles per hour on six different occasions.  

Preliminary results are encouraging. INRIX speed data shows that drivers largely conformed and reduced their speeds significantly within the time periods the VSL's were activated and displaying reduced speed limit information. Additionally, the Crash Data Analysis Retrieval Tool (CDART) showed an 80 percent reduction in the number of crashes during those same time frames in 2021 and 2022. There were seven crashes in 2021 and just three in 2022. 

The early successes of this pilot program prompted District 2 to purchase a total of 22 units for deployment in Clearfield and Clinton counties for the 2022-23 winter maintenance season. The 14 units deployed during the pilot were rentals. The deployment period will begin in October and conclude in April, and units will be stationed near existing permanent speed limit signs that will be covered during the period of the deployment.  

The expansion of the program is not exclusive to District 2. Other areas with significant crash histories have been identified and will see deployments this winter as well. Districts 4, 5 and 8 will see a total of 36 units deployed (seven in Luzerne County; 24 in Schuylkill County; and 5 in Lebanon), District 10 will deploy six units between Clarion and Jefferson counties.  

Since the units are portable, District 2 is evaluating the equipment for potential use in alerting motorists of crashes or summer maintenance projects such as seal coating or other slow-moving operations. 

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