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The National Academies

NCHRP 22-37 [Active]

Development of a MASH Barrier to Shield Pedestrians, Bicyclists, and Other Vulnerable Users from Motor Vehicles

  Project Data
Funds: $450,000
Staff Responsibility: Ann M. Hartell
Research Agency: Texas A&M Transportation Institute
Principal Investigator: Dr. Chiara Silvestri Dobrovolny
Effective Date: 5/3/2019
Completion Date: 1/2/2022

BACKGROUND

As the number of pedestrians, bicyclists and users of other active transportation modes continues to grow in the United States, state departments of transportation (DOTs) are seeking to improve how these users are accommodated on or adjacent to our nation’s roadways. Despite these efforts, some roadways have limited lateral offsets between the motor vehicle travel lanes and the sidewalks or multi-use paths that can reduce actual and/or perceived safety for these vulnerable users. When available right-of-way and/or project funding constrain transportation agencies’ ability to increase this offset distance, an alternative can be to install a positive protection device—a barrier that separates lanes for motorized vehicles and facilities for vulnerable users.
 
Traditionally, barriers are designed for a specific need such as shielding motorists from a steep slope or a fixed object in the clear zone. The selection of a barrier is driven by roadway design speed, traffic volume, and clear zones, along with considerations such as the accommodation of access points, climate conditions, and aesthetics. However, the use of barriers to separate pedestrians and bicycles from motor vehicles requires the consideration of additional factors to address safety for all users. For example, a typical guardrail is designed to redirect motor vehicles, but may not be tall enough to protect pedestrians by preventing inadvertent encroachment into the roadway. Guardrail designs may have bolts or other features that can snag a vulnerable user. Geometric conditions, such as a vertical separation between the motor vehicle travel lanes and the pedestrian or bicycle facility, may change the performance of the barrier. Additionally, when struck by a motor vehicle, a barrier may deflect into the path of a vulnerable user. While a concrete barrier can satisfy many requirements, alternative, lower-cost designs are needed, especially designs with open railings that allow visibility.
 
Previously published guidance includes some information on barrier designs to separate vulnerable users from motor vehicle traffic; however, design specifics are incomplete and may not address the most common design contexts where a new barrier or modification to an existing barrier is needed for positive protection.
 
Research is needed to develop a barrier with design and performance characteristics that address safety for vulnerable users and for motorists while satisfying the proposed Public Right-of-Way Accessibility Guidelines (PROWAG) and the American Association of State Highway and Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH) criteria. To ensure a design is appropriate for commonly encountered design contexts and challenges, it must be informed by a review of current practice that identifies gaps between current practice and crashworthy barrier solutions.
 
OBJECTIVE
 
The objective of this research is to develop a minimum of one nonproprietary barrier design for use in separating vulnerable users from motor vehicle travel lanes that is tested to appropriate MASH criteria, complies with PROWAG, and is cost-effective. An acceptable design could be for a completely new barrier or one that modifies an existing barrier. The barrier design shall provide positive protection by redirecting motor vehicles and include design elements that also increase safety of vulnerable users. The barrier design should be appropriate for commonly encountered design contexts.

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