How to Combat the Horizontal Curve Roadway Fatality Problem

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We’ve all done it: driving around a curve too fast. You straighten your back in the driver’s seat, focusing on steadying the vehicle as you make your way around the curve. That was uncomfortable. You wish you would have known to go slower. The good news is you successfully made the curve without accident, and if you drive in this area again, you’ll remember to slow down. However, not everyone has the same fate.

Horizontal Curves Exhibit High Crash Rates

Remember Tiger Woods’ infamous crash? While high speed was a factor in his crash, an S curve was a critical variable too. In fact, the average crash rate is three times greater on a horizontal curve, according to the Federal Highway Administration (FHWA). And out of all fatal roadway departures, the FHWA informs us that 25% take place on horizontal curves.

Horizontal curves are a big deal, especially with many transportation professionals working toward initiatives like Vision Zero. Vision Zero aims to reduce and prevent fatal traffic accidents by recognizing that 1) roadway fatalities are preventable and 2) saving lives can be inexpensive with a systemic approach.

Why Are Horizontal Curves So Dangerous?

Before implementing low-cost countermeasures on your horizontal curves, it’s good to understand why roadway departures are so common on highway curves. Combine driver fatigue, rural areas with poor lighting and unsuspecting curves — and you’ve got the recipe for an accident! And let’s not forget speeding. High speeds and curves don’t mix well, but it’s not just Tiger Woods — the National Highway Traffic Safety Administration reported that in 2020, speeding was on the rise in both rural and urban areas.

A simple internet search for dangerous roadways will leave your results page littered with lists of the top dangerous highways across the continental United States. The bottom line: there’s a lot of dangerous roads. And no doubt that these same dangerous highways contain horizontal curves. In being committed to safer roads and fewer roadway fatalities, where do you start?

Identify What Makes Your Horizontal Curve Dangerous

Once you understand why your horizontal curves produce high numbers of roadway departures, it’s time to implement change. We’ve paired up the best, low-cost countermeasures to combat horizontal curve fatalities.

  • S Curves: When it comes to curves, the danger lies within the change of direction. When there are back-to-back changes in directions, the potential for danger naturally increases. S curves can greatly benefit from sequential flash pattern chevrons that help guide road users through the curve and are proven to reduce fatal crash rates up to 60%.
  • Rural Roadways: Often, in rural areas, horizontal curves seem to appear without warning, leaving drivers in unexpecting circumstances. For rural areas, advance warning signs make a great addition to your dynamic curve warning system.
  • Speeding: If your horizontal curve often frequents speeders, installing a radar feedback sign alongside your dynamic curve warning system may curb the undesired behavior and help prevent crashes.

Other system enhancements can be added too, depending on your horizontal curve’s specific needs: from message boards that alert speeding drivers who are going too fast for a curve to event management software that enables you to get the most out of your system. For each horizontal curve, there is a systemic approach waiting to be implemented in order to decrease roadway fatalities and save lives.


Learn more about countermeasures to tackle horizontal curve fatalities >

Aleischa Kronshagen

TAPCO | Product Manager

With several years of experience in the traffic safety industry, Aleischa manages TAPCO's dynamic curve warning solution product line and most other specialty solution product lines, including emergency vehicle, icy road and intersection conflict.

Previously, she was a member of TAPCO's customer service team, which fostered a passion for process and data analysis, as well as creative problem solving.

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