Every year, single vehicle, run-off-the-road crashes account for a large percentage of motor vehicle crashes. Some of these crashes take place along sharp curves, which typically contain chevron signs designed to warn and safely guide motorists through the area. The static, black and yellow signs are a beneficial safety tool, but some motorists might notice a new, brighter upgrade along roadways to help guide their way.
A Sequential Dynamic Lighting Curve Warning System, also known as lighted chevrons, is a system of sequentially flashing chevron signs that can help guide motorists through curves. Championed by the State Transportation Innovation Council (STIC), the Sequential Dynamic Lighting Curve Warning System is one of many tactics that can be used along curves and can be especially helpful to motorists driving in substandard weather conditions, including fog, snow and rain, as well as driving at night and through work zones. The network behind the LED-enhanced solar or electric powered signs continuously communicates and provides a synchronization pulse to ensure the signs flash in proper order.
The first time Ryan Collins, Highway Safety Unit manager in PennDOT Engineering District 2, saw the system in action was while he was driving on Interstate 81 in Virginia.
“They were flashing, and I'm like, 'What is that flashing?'" he said. “When I was going [down I-81], there wasn't heavy fog but enough to hinder your sightlines. I saw these flashing devices, and they assisted me through the curve, and I thought 'Wow, that's pretty amazing!'"
Collins shared the information with members of his leadership team in the Clearfield-based engineering district, who were already aware of the lighted chevrons due to multiple pilot projects that had occurred in other PennDOT engineering districts.
By evaluating speed and safety data, Collins and his team chose three pilot locations to implement the lighted chevrons in 2022. The data indicated three locations that experienced lane departure and truck rollover crashes: I-99 in Centre County, Route 322 in Centre County and Route 22 in Mifflin County. The areas already had multiple countermeasures, such as static chevrons, curve warning treatments and pavement markings on the road, but the problems persisted in these locations. Collins and his team hoped to test the Sequential Dynamic Lighting Curve Warning System at these locations to see whether it could have an impact..jpg)
During the design phase, Collins and his team considered various technical aspects. They chose locations with access to direct sunlight and made the necessary field adjustments to ensure the solar-powered signs got consistent power. They also installed heavier brackets since the oversized signs need to sustain the weight of the sign as well as environmental factors like wind load.
Collins' team received immediate positive feedback from the public once the system was implemented in these locations.
“Folks that live around [Centre County], and now in Mifflin County, believe [these devices] are truly making a difference," Collins said.
Collins and his team will gather and study data from these three locations, including a 5-year analysis to gather more extensive data. He hopes that future safety countermeasures will help end all crashes.
“I'm passionate about safety," he said. “I'm all for what we can do to engineer things and make things safer for motorists. [PennDOT is] taking strides in improving highway safety. Pennsylvania's goal is zero fatalities, and that is my goal. That is our goal."
Every year, Pennsylvania performs numerous engineering improvements to combat crashes and enhance safety on our highways. The Sequential Dynamic Lighting Curve Warning System is still being investigated to determine its impact on highway safety.
Visit www.PennDOT.pa.gov/Safety for more information on safety infrastructure improvement programs and safety countermeasures PennDOT implements throughout the state.