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Crashworthiness of Roadside Hardware on Curbed Roadways

Description:

Roadside hardware is often installed alongside curbed roadways. The standardized full-scale roadside hardware crash test procedures, however, do not normally include curb near or around the tested roadside safety feature. Although it is generally recommended to not install roadside safety features behind curbs, it is often necessary to do so along roadway corridors where curbs are needed. There has been some previous research examining the effects of curbs in front of longitudinal barriers but there is relatively little known about the effect curbs on the impact performance of common roadside safety features, especially guardrail end terminals, crash cushions, and breakaway hardware. The objective of this project would be to determine the effect of curbs on the impact performance of various roadside hardware devices. The approach could be to use in-service performance evaluation, full-scale crash testing, computer simulation or some combination of these methods.

Objective:

The objective of this project would be to determine the effect of curbs on the impact performance of various roadside hardware devices. The approach could be to use a combination of in-service performance evaluation, full-scale crash testing, and computer simulation.

a. The expected outcome of this research will be guidance for incorporation in the AASHTO Roadside Design Guide. The final product will include guidance to agencies for the placement of roadside hardware behind curbs and when it should be avoided.

b. The research contractor will likely have to perform these major tasks:

·

Compile available roadside hardware inventories and on-road inventories which note the presence/absence of curb. These inventories should be matched with available crash records to conduct a routine ISPE, as outlined in NCHRP 22-33.

·

Supplement the findings of the ISPE task by performing computer simulations to refine placement which allows for the MASH criteria to be achieved.

·

Conduct some base-line crash testing for verification and validation of simulation models.

c. This research will result in guidelines for incorporation in the AASHTO Roadside Design Guide.

d. Provide recommendations for any additional crash testing requirement that should made to the AASHTO Manual for Assessing Safety Hardware (MASH) for hardware intended for use adjacent to curbs.

Benefits:

The influence of curbs on traffic safety devices is an on-going complication to the safety of the traveling public. The need to identify the most common safety devices and the effect of a curb on the functionality of the device will provide a measure of assurance in the choice and placement of traffic safety devices and a higher level of safety for the traveling public.

State Transportation Agencies continue to strive to reduce the frequency and severity of run off the road crashes while balancing community and environmental needs, accommodation of utilities, and effective use of limited transportation budgets. This research will develop objective guidance for the use of roadside safety features behind curb. This research will quantify the crash risk and will provide guidance which allow engineers to balance the competing need for both curbing and roadside safety features. It is anticipated that the results of this research will be incorporated into a future update of the AASHTO Roadside Design Guide. State Transportation Agencies may utilize this research as a foundation for policy development for the use of curbing in combination with roadside safety features. Continuing without such guidance will result in the continued suggestion to not install curbing in conjunction with roadside safety features, which severely limits the design alternatives for drainage and roadside safety.

Related Research:

A literature search resulted in the identification of NCHRP Report 357 (Recommended Guidelines for Curb and Curb–Barrier Installations) by Plaxico et al., which was concerned with the performance of w-beam guardrail installed in conjunction with curbing. A project to update Report 357 for MASH w-beam guardrail has been funded. The literature search showed that no research is available on the performance of any other roadside safety features (e.g., terminals, signs, crash cushions, etc.) installed in conjunction with curbing and there are no projects funded for extending the Report 357 findings to any other roadside safety features (e.g., terminals, signs, crash cushion, etc.).

Carrigan et al. are currently developing a Guidance Document for the conduct of ISPEs under NCHRP 22-33, “Multi-State In-Service Performance Evaluations of Roadside Safety Hardware.” A pilot test of the NCHRP 22-33 research products is in the beginning stages. The ISPE techniques presented in NCHRP 22-33 could be further implemented (beyond the pilot test) in this proposed research for the ISPEs of roadside safety features installed with curb. The pending project for “Development of a Crash Data Collection Tool and Application Guidelines for MASH In-Service Performance” will likely result in research which can be used to collect field inventory information regarding the location of curbing and roadside safety features.

There is a need to develop objective guidance for the placement of roadside safety features in addition to w-beam guardrail in combination with curbing. This research will build on the guidance provided in MASH, the nearing completion NCHRP 22-33 and the guidance documented in NCHRP Report 357 to expand the body of knowledge beyond w-beam and curb combinations.

Tasks:

The approach could be to use a combination of in-service performance evaluation, full-scale crash testing, and computer simulation.

a. The expected outcome of this research will be guidance for incorporation in the AASHTO Roadside Design Guide. The final product will include guidance to agencies for the placement of roadside hardware behind curbs and when it should be avoided.

b. The research contractor will likely have to perform these major tasks:

· Compile available roadside hardware inventories and on-road inventories which note the presence/absence of curb. These inventories should be matched with available crash records to conduct a routine ISPE, as outlined in NCHRP 22-33.

· Supplement the findings of the ISPE task by performing computer simulations to refine placement which allows for the MASH criteria to be achieved.

· Conduct some base-line crash testing for verification and validation of simulation models.

c. This research will result in guidelines for incorporation in the AASHTO Roadside Design Guide.

d. Provide recommendations for any additional crash testing requirement that should made to the AASHTO Manual for Assessing Safety Hardware (MASH) for hardware intended for use adjacent to curbs.

Implementation:

The results of this research will be used by state standards engineers to update the standard drawings and design manuals to provide guidance on the installation of roadside safety features in conjunction with curbing. The AASHTO TCRS could assist implementation through adopting the research results in the AASHTO Roadside Design Guide. Implementation could also be supported through a discussion of the findings at an TRB AFB20 meeting and the conduct of the TRB webinar.

Relevance:

The AASHTO Strategic Highway Safety Plan and the FHWA Roadway Departure Strategic Plan both highlight the importance of reducing the incidence and severity of roadside crashes. The AASHTO Technical Committee on Roadside Safety has also prioritized the combined use of ISPEs, computer simulation, and full-scale crash testing in its strategic plan.

Sponsoring Committee:AFB20, Roadside Safety Design
Research Period:24 - 36 months
Research Priority:High
RNS Developer:Christine Carrigan and Jean Vedenoff
Source Info:TRB AFB20 Mid-Year Meeting 2019, Reno NV
Date Posted:01/06/2020
Date Modified:01/06/2020
Index Terms:
 
Subjects    
Highways
Design
Safety and Human Factors

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