Insights

Get Ahead of the Curve: Combatting Run-off-the-Road Collisions

Of all fatal road crashes in the United States, an estimated 53 percent are roadway departure crashes and 28 percent are associated with horizontal curves, according to the Federal Highway Administration (FHWA). Regions with challenging, mountainous terrain have some of the highest run-off-the-road rates in the nation due to sharply curved roadways. Drivers in these areas also often face additional challenges that contribute to the issue, such as inconsistent or outdated speed postings.

Determining the Problem

For a variety of reasons, it is not uncommon for incorrect speeds to be posted.  An incorrect posted speed at one curve results in a driver disregarding a speed at another curve. For instance, if the advisory speed for a curve is 30 miles per hour (mph) but a 25 mph sign is posted and the driver safely travels through the curve at 30 mph, drivers may assume they can safely exceed the advised speed at other curves. When these drivers are faced with a roadway curve that has an accurate speed posted, the consequences of exceeding it could be fatal.

One reason for incorrect advisory speed postings is that they may be outdated. Over time, vehicles have become safer, smarter, and capable of safely handling higher speeds than in the past, making older speed postings inaccurate. These conditions can lead drivers to a habit of violating advised speeds. 

This national concern has prompted the FHWA to take corrective action by establishing a mandate for all horizontal curve signs to be updated by the end of 2019. The Manual on Uniform Traffic Control Devices (MUTCD) outlines the changes to be made including curve warning signs based on curvature and distance. Making these changes can be a difficult and time-consuming process, but just as vehicles have become smarter, so have the methods used to determine the right curve speeds.

Smarter Technology for Safer Roads

The new, fully-automated Curve Advisory Reporting Service (CARSTM) software makes collecting data easier, faster and more accurate. Prior to this new technology, curve speeds were determined using the old ball bank and gauge method which was time consuming and often inconsistent due to user subjectivity. The CARSTM software utilizes GPS technology which increases data accuracy and decreases the time spent collecting data. By leveraging GPS, this is the only method that doesn’t require the driver collecting the data to turn around at every curve. Additionally, the software has the following features:

  • Automatically determines curve radius, superelevation, and vertical profile
  • Automatic sign placement and recommendation reports
  • Auto-saves to a secure cloud
  • Customizable, searchable and downloadable data

Implementing the Solution

To promote this initiative and help reduce these crashes, the FHWA funded a roadway departure study in West Virginia in which B&N leveraged CARSTM technology to evaluate 260 miles of State and U.S. routes. According to their latest research, 71 percent of all fatal roadway accidents in West Virginia are run-off-the-road crashes, making it one of the most at-risk states in the nation.

During the study, B&N assessed over 1,000 curves. The findings revealed that most of the curves had advised speed postings that were incorrect or outdated. As a result, over 8,500 new signs were recommended.

As the FHWA mandate deadline approaches and fatal, run-off-the-road crashes continue to occur, it is becoming increasingly important for roadway owners to take steps toward updating curve advisory speeds and signage. There are several resources available to assist owners with making the updates including the FHWA’s Low-Cost Treatments for Horizontal Curve Safety publication and the Transportation Research Board’s Guide for Reducing Collisions on Horizontal Curves. For more information on horizontal curve safety and treatments, contact B&N’s roadway experts. 

Kendra Schenk, PE, PTOE, RSP, Transportation Engineer
Kendra Schenk, PE, PTOE, RSP
Transportation Engineer