The National Academies

NCHRP 22-52 [Anticipated]

Development of a Crashworthy Tangent End Treatment for Low Speed Curbed Roadways

  Project Data
Source: AASHTO Committee on Design, Technical Committee on Roadside Safety
Funds: $750,000
Staff Responsibility: Ann M. Hartell
Fiscal Year: 2022

This project has been tentatively selected and a project statement (request for proposals) is expected to be available on this website. The problem statement below will be the starting point for a panel of experts to develop the project statement.

With the increasing interest in multimodal transportation, the demand for appropriate barrier solutions to address roadside safety issues in low-speed urban and suburban conditions has increased. These environments often have closely spaced intersections/driveways, improvements intended to encourage bicycle and pedestrian travel, physical limitations to the available lateral offset, and commonly involve curbed roadways sections. Because of the physical space limitations, barriers have been installed without a crashworthy end treatment (e.g., sloped end treatments on concrete barrier). Systems that have not been evaluated for use in combination with curbs (e.g., crash cushions) and/or those that involve compromises with respect to length of need (i.e., use of gating hardware) have also been installed.  Because barriers in these locations are normally installed in combination with curbing, terminals commonly cannot be flared to avoid conflicts with adjacent pedestrian or bicycle accommodations. 

As a result of these constraints, a viable end treatment for barriers in these environments—whether for new construction or retrofits of existing barriers—should minimize:

·         Lengthto allow for installations along roadways with longitudinal constraints (i.e., discontinuities for intersections, driveways, predestination crossings, etc.).

·         Widthto reduce impacts on infrastructure and adjacent pedestrian pathways.

·         Heightto reduce impacts on sight distance and allow for use with low profile barriers, guardrail, and typical concrete barriers/bridge traffic railings shapes.

The objective of the research is to develop an AASHTO Manual for Assessing Safety Hardware (MASH) TL-2 Tangent End Treatment that minimizes the required length, width, and height of the system, and can be used in common conditions found in urban and suburban areas—specifically in combination with 6” vertical curb (minimum height)—and that can be transitioned into either TL-2 low profile, TL-3 F-shape concrete, and semi-rigid w-beam barrier systems. The end treatment should be evaluated using a combination of ISPEs, computer simulation, and full-scale crash testing. The final product will be non-proprietary system drawings and specifications that will allow for component manufacturing and installation.

Potential tasks include:

·         Comprehensive literature review to determine critical design elements, evaluate potential components, and establish baseline for system design concepts.

·         Review related current and expired patents to ensure a non-proprietary system can be developed.

·         Determine appropriate curb heights.

·         Develop design concepts.

·         Perform component/material testing.

·         Perform computer device simulations of selected concepts.

·         Proof of concept crash testing.

·         Validation of computer simulations.

·         Full scale crash testing to MASH TL-2 terminal/crash cushion testing matrix.

·         Development of design drawings and construction specifications needed for the manufacturing and installation of the system.

·         Develop design drawings of concepts for commonly needed transitions.

·         Submit drawings for inclusion in the Task Force 13 Hardware Guide.

·         Presentation of final design to AASHTO Technical Committee on Roadside Safety and TRB Roadside Design  Committee.


Direction from the AASHTO Special Committee on Research & Innovation: Consider the use of simulation to minimize crash testing to develop a generic system.  Consider NCHRP project 15-53, “Roadside Barrier Designs Near Bridge Ends with Restricted Rights of Way” and avoid duplication of effort.

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