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#RRSAW2024 Day 3: Sharp Curves

Rural roadway scenery often includes winding roads that disappear into the horizon. These winding road types have horizontal curves and are very common on rural two-lane roads.

As beautiful as they are, horizontal curves can become a risk when drivers do not immediately notice them upon their approach, which increases the risk for a roadway departure (RwD).

The overall theme of Rural Road Safety Awareness Week (RRSAW) is, “Life Between the Lines: Preventing Rural Roadway Departures.” For Day 3, we are focusing on sharp curves and the life-saving countermeasures that can make them safer for all road users.

Curves have an impact on traffic crashes.

  • 42% of rural RwDs fatal crashes happen at curves.
  • 75% of curve-related fatal crashes involve single vehicles departing the roadway and striking a fixed object or overturning.
  • The average crash rate for horizontal curves is about three times that of other types of highway segments.

 

A variety of countermeasures that prevent and reduce RwD at sharp curves are available to rural road practitioners. For example, by installing chevrons at curves, nighttime crashes can be reduced by 25 percent. Edge and center line markings, appropriate curve advisory speeds, friction treatments, and rumble strips/stripes are more examples of countermeasures that help prevent RwDs at curves.

ChevRon

Wooosh! No sharp curve is left untouched when ChevRon is on the rural road. ChevRon flattens slopes on the outside of curves, deploys chevrons, implements dynamic curve warning systems, and installs speed advisory markings.

To see ChevRon in action, click the image below.

Resources

Safe System Approach (SSA)

Regarding curves, the Safe Roads element of SSA promotes traffic control devices that alert road users to an approaching curve and the operating speed. These devices, paired with road design that help keep vehicles in their lane and reduce the potential and severity of crashes, can save lives at rural curves.

Everyday actions that reduce RwDs

  • Educate road users about horizontal curves and the signs, pavement markings, and other tools that make them safe.
  • Consider creating clear zones, improving pavement friction, installing SafetyEdgeSM, and maintaining traversable roadside slopes.
  • Develop a method/plan to maintain minimum retroreflectivity for signs and pavement markings.

More

  • Why do Cars stay on the road in a curve? – Centripetal Forces Explained! | Watch Video
  • Pavement Cross Slopes and Vehicle Dynamics | Watch Video
  • Systemic Analysis | Watch Video
  • Rural Roadway Departure Countermeasures Pocket Guide | View pdf
  • Enhanced Delineation for Horizontal Curves (FHWA Proven Safety Countermeasure) | View Website
  • Roadside Design Improvement at Curves (FHWA Proven Safety Countermeasure) | View Website
  • FHWA Curve Signing Storyboard | View Storyboard
  • Curve Signing: Proper Chevron Spacing | Watch Video
  • Curve Signing: Proper Placement in the Field | Watch Video
  • “Lookout! Curves Ahead” Setting Curve Advisory Speeds | View Webinar
  • FHWA Minimum Pavement Marking Retroreflectivity Playlist | View Playlist
  • Nighttime Visibility Sign Retroreflectivity – Implementation Tools | View Webpage
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