SUMMARY
Development of a MASH Barrier to Shield Pedestrians, Bicyclists, and Other Vulnerable Users from Motor Vehicles
The number of vulnerable road users continues to grow within the United States, as do crashes between motorists and vulnerable road users. Vulnerable users such as pedestrians and bicyclists are expected to jointly use facilities that have constrained lateral offsets between the travel lanes and vulnerable user transportation facilities such as sidewalks and multiuse paths. On many of these facilities, right of way (ROW), fiscal, or geographical constraints prohibit transportation agencies from increasing the offset distance.
At present, no positive barrier systems have been designed specifically for the purpose of providing positive protection between vulnerable user transportation facilities and motorized facilities. A critical need exists to develop new multifunctional barrier systems that comply with the specific accommodation requirements of pedestrians, bicyclists, and motor vehicles. Such a system should ideally be affordable from a constructability and installation standpoint, be appealing from an aesthetic perspective, take into consideration adequate and proper sight distance, and be designed to safely contain direct hits from motorized users.
The objective of this research was to develop a barrier that accommodates the safety needs of pedestrian, bicyclist, and motor vehicle traffic. In developing a new barrier design, consideration was given to commonly encountered design contexts such as the test standards of the Manual for Assessing Safety Hardware (MASH) and the criteria of the Public Right-of-Way Accessibility Guidelines. This research consisted of eight tasks to meet the objectives of NCHRP Project 22-37, “Development of a MASH Barrier to Shield Pedestrians, Bicyclists, and Other Vulnerable Users from Motor Vehicles.”
The research team identified and reviewed relevant national and international literature and standards that included methodology and related research about the physical separation of pedestrians or bicyclists and motor vehicles. The researchers identified several sources of information regarding the needs of both crashworthy roadside barriers and vulnerable users. The research team also solicited information from transportation agencies; design consultants; vulnerable user groups; and, as appropriate, transportation agencies outside the United States on typical project types and design contexts where a tested barrier to separate motor vehicles from vulnerable users is needed.
The research team then developed a nonproprietary barrier for use in separating pedestrians, bicyclists, and other vulnerable users—including people who use a wheelchair and people with visual impairments who use canes—from motor vehicles. Six barrier design options were proposed, with ratings based on their anticipated advantages and disadvantages for further investigation through computer simulation. On the basis of discussions with the research panel, finite element simulations and full-scale crash tests were conducted on a
selected barrier design, and the barrier met the requirements of MASH Test Level 3 (TL-3) (high speed). The barrier is considered appropriate for a variety of contexts, such as where ROW constraints reduce lateral offset between a roadway and a shared-use path.
It was noted that implementation of the barrier by state departments of transportation (DOTs) required a transition system to standard guardrail. Thus, as part of the project, the research team developed a design that transitioned the new multifunction barrier system to conventional strong-post W-beam guardrail. Different transition designs were proposed and investigated through computer simulations. A Thrie beam transition system was selected and incorporated design details on the upstream end that have been previously evaluated and are considered MASH compliant. The downstream end of the Thrie beam transition design was further investigated through full-scale crash testing according to MASH TL-3 criteria, which included MASH Test 3-20 and MASH Test 3-21. Full detailed drawings of the successfully tested multifunctional barrier and associated transition design are included in this report.
