NCHRP Research Report 1116: Development of a MASH Barrier to Shield Pedestrians, Bicyclists, and Other Vulnerable Users from Motor Vehicles provides a detailed design for a crashworthy roadside barrier system for use alongside high-speed roadways that also addresses the needs of nonmotorized users of adjacent multiuse facilities. The report and accompanying resources will be of interest to highway designers seeking a design solution for locations where nonmotorized transportation facilities are adjacent to high-speed roadways.
As the number of pedestrians, bicyclists, and users of other active transportation modes continues to grow in the United States, state departments of transportation and other transportation agencies are seeking to improve how these users are accommodated on or adjacent to our nation’s roadways. In many locations, limited lateral offsets between the motor vehicle travel lanes and the sidewalks or multiuse paths can reduce actual and perceived safety for these vulnerable users. When the available right-of-way constrains the ability to increase offset distance, an alternative can be to install a positive protection device—a barrier that separates lanes for motorized vehicles and facilities for nonmotorized users. 

Traditionally, barriers are designed for a specific need such as shielding motorists from a steep slope or a fixed object, such as a pole or tree. The selection of a barrier is driven by roadway design speed, traffic volume, clear zones, aesthetics, and accommodation of driveways and other access points, snow plowing, and stormwater runoff. However, the use of barriers to separate pedestrians and bicycles from motor vehicles requires the consideration of additional factors. For example, a typical guardrail is designed to redirect motor vehicles but may not be tall enough to protect pedestrians or bicyclists by preventing them from inadvertently encroaching on the roadway. Guardrail designs may have bolts or other features that can snag a wheelchair or bicyclist. A barrier that has gaps between posts may be difficult for people with limited vision to detect with a cane or other mobility device. When struck by a motor vehicle, a barrier may deflect into the path of a nonmotorized user on the adjacent facility.

Under NCHRP Project 22-37, “Development of a MASH Barrier to Shield Pedestrians, Bicyclists, and Other Vulnerable Users from Motor Vehicles,” the Texas A&M Transportation Institute was tasked with reviewing existing barrier designs and policies related to safety barriers that separate nonmotorized users from motor vehicles. From this review, design requirements for a new barrier were identified. A preferred design was selected for detailed development and was assessed for impact performance by using finite element computer impact simulations. Finally, a full-scale installation of a refined barrier design was constructed and tested for crashworthiness in accordance with Test Level 3 (TL-3) of the Manual for Assessing Safety Hardware (MASH). The barrier was also assessed for comfort and acceptability for people who use wheelchairs, people with limited vision who use canes as a mobility device, pedestrians, and bicyclists. Separate computer simulations and full-scale crash tests were also conducted to assess the crashworthiness of a Thrie beam transition to connect the new barrier to a typical W-beam guardrail.

NCHRP Research Report 1116 presents a nonproprietary, crashworthy design for use in separating vulnerable users from motor vehicle travel lanes that is: 

• Tested to the TL-3 criteria (high-speed roadway application) established by AASHTO’s Manual for Assessing Safety Hardware,

• In compliance with the U.S. Access Board’s proposed Public Right-of-Way Accessibility Guidelines (PROWAG),

• Appropriate for a variety of design contexts, and

• Compatible with W-beam guardrail using a Thrie beam transition.

The report includes detailed drawings of the barrier and the transition designs to provide designers with a barrier system that is ready for implementation. Accompanying the report are a set of presentation slides summarizing the project, a memorandum describing activities to promote the adoption and implementation of the new system, a video of all full-scale tests, and 10 appendices provided in two files:

• “Technical Drawings and Information for FHWA Eligibility Filing: Appendices B, E, F, and J” (Appendices B, E, and F are also included in this report) and

• “Survey, Crash Test Data, and Supporting Certification Documents: Appendices A, C, D, G, H, and I.”

All of these materials can be found on the National Academies Press website (https://doi.org/10.17226/27896) web page for NCHRP Research Report 1116 under “Resources.”