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Sequential Dynamic Chevron Warning System | Safe Design

Sequential Dynamic Chevron Warning System

Image Source: Iowa State University Center for Transportation Research and Education

DEFINITION AND DESCRIPTION

A sequential dynamic curve warning system (SDCWS) consists of a series of solar-powered LED chevron signs installed along a curve. Signs flash in sequence when a radar or another detection device detects approaching vehicles, alerting drivers to reduce their speeds as they navigate the curve. They can replace existing chevrons and are beneficial in low-visibility conditions. 

Implementation Categories

Area(s) Traffic Operations, HSIP
Safety Category 4

CONSIDERATIONS

  • Requires a radar detection system.  Some applications include a constant flash.
  • Requires solar power.
  • May need to set speed thresholds.
  • Consider friction curve data and potential collisions with signs.
  • Lowers speeds and reduces crashes (Smadi et. al., 2015).

APPLICATION

  • May be considered on high-speed facilities along sharp curves with poor safety performance.
  • See MUTCD Section 2A.12 for guidance on the use of LEDs with signs.

example

Pennsylvania DOT (PennDOT) piloted SDCWS in several locations and is developing a statewide approval process for sign installations. Its specifications have been updated to include flash rates, five acceptable colors, dimming, optional traffic detection, and flashing sequence. Requirements are documented in the agency’s Qualified Products List. 

Complementary SSA Strategies

REFERENCES AND RESOURCES

Hallmark, S., J. Wood. “Synthesis of the Effectiveness of Low-Cost Countermeasure for Rural Curves” [PowerPoint presentation]. TRB Roadside Safety Conference, Orlando. Fl. 2024, June.

Pennsylvania State Transportation Innovation Council. Sequential Dynamic Lighting Curve Warning Systems – Lessons Learned. https://www.penndot.pa.gov/about-us/StateTransportationInnovationCouncil/Innovations/Documents/Sequential%20Dynamic%20Lighting%20Curve%20Warning%20Systems-%20Lessons%20Learned%20FINAL.pdf

Smadi, O., N. Hawkins, S. Knickerbocker, S. Hallmark, A. Pike. Evaluation of the Sequential Dynamic Curve Warning System – Final Report. FHWA Report 15-CAI-012-B. 2015. Federal Highway Administration, Washington D.C. https://www.fhwa.dot.gov/hfl/partnerships/tapco/final_report.pdf

Do you have more questions? Get in touch!

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CONTACT:

Jill Asher

Research Engineer 

jill.asher@uky.edu