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Roadway Departure Safety (Part 3 of 3)

Edited by Airton G. Kohls and Matt Cate (Source: FHWA Office of Safety)

 

This is the final article in our series about reducing roadway departure (RwD) crashes. Roadway departure crashes encompass a variety of crash scenarios, including collisions between vehicles traveling in opposite directions on the same roadway, vehicles striking terrain and drainage features, and collisions with fixed objects such as trees and utility poles.

Our focus today is on countermeasures to reduce crash severity. It is one of the efforts presented on the FHWA’s Strategic Approach & Plan that also includes strategies to keep vehicles on the roadway and to provide for safe recovery.

Figure 1 - Example testing of a traffic signal pole impacted by a vehicle travelling at 60 mph

Countermeasures to Reduce Crash Severity

Hardware, such as barriers, sign and traffic control device supports, and work zone devices are commonly used to reduce the potential severity of crashes on the roadside. Crash testing is used to evaluate the crashworthiness of these devices.

The American Association of State Highway Transportation Officials (AASHTO) provides guidance related to the design and installation specifications of roadside hardware and safety hardware. Understanding the performance of roadside safety hardware begins in a controlled, sterile laboratory environment using crash test scenarios and standards set and maintained via AASHTO’s Manual on Assessing Safety Hardware (MASH). Figure 1 on page 3 is an example of such tests, where a vehicle traveling at 60 mph hits a traffic signal pole. However, laboratory tests cannot completely protect against all of the variables and countless situations drivers may find themselves in. Therefore, FHWA encourages states to perform inservice performance evaluations to identify real world performance of hardware so all stakeholders have a more comprehensive understanding of these devices’ performance. For more information about in-service performance evaluation of roadside safety devices, please visit https://safety.fhwa.dot.gov/roadway_dept/countermeasures/reduce_crash_severity/guardrail_ispe.cfm

 
 

AASHTO Guidance

The Roadside Design Guide presents a synthesis of current information and operating practices related to roadside safety and focuses on safety treatments that can minimize the likelihood of serious injuries when a motorist leaves the roadway.

The Manual for Assessing Safety Hardware (MASH) presents uniform guidelines for crash testing permanent and temporary highway safety features and recommends evaluation criteria to assess test results.

class="para_title"TDOT Guidance

Information on safety barriers for the State of Tennessee can be found at TDOT’s Safety Design and Fences webpage https://www.tn.gov/content/tn/tdot/roadway-design/standard-drawings-library/standard-roadway-drawings/safety-design-and-fences.html

Additional Guidance

FHWA also provides Roadside Hardware Resource Charts on aesthetic barriers, cable barriers, cast-in-place concrete barriers, crash cushions, median terminals, roadside post and beam, roadside terminals and work zone barriers at https://safety.fhwa.dot.gov/roadway_dept/countermeasures/resources.cfm

These charts were developed by FHWA as a tool for selection and identification of various roadside hardware systems to be used by field and design personnel. The information on these charts was extracted from a number of sources, but users should contact the manufacturer for more detailed information. Every available system is not necessarily included on the charts. These are NOT approved product lists.


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