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Development of a Barrier Design to Accommodate Vehicles, Pedestrians, and Cyclists

Description:

There is an urgent need to foster the development, operation and maintenance of an integrated national transportation system, which gives consideration to the presence and safety of non-motorized users. As the number of non-motorized users continues to grow within the US, crashes between motorists and non-motorized users continue to grow as well. Based on National Highway Traffic Safety Administration (NHTSA) data from 2015, 5,376 pedestrians and 818 bicyclists were killed in crashes with motor vehicles. These two modes accounted for 17.7 percent of the nation’s 35,092 total fatalities in 2015. Unfortunately, a large percentage of our nation’s roadways are not designed to safely accommodate non-motorized users. Thus, non-motorized users such as pedestrians and bicyclists are expected to jointly use facilities that have inadequate lateral offsets between the travel lanes and the non-motorized transportation facilities such as sidewalks and multi-use paths. On many of these facilities, ROW, fiscal, and/or geographical constraints prohibit transportation agencies from increasing this offset distance, which leaves agencies with the option of doing nothing or trying to fit some type of positive protection device in between the travel lanes and the non-motorized transportation facility. Currently, there are no positive barrier systems that have been designed specifically for the purpose of providing positive protection between non-motorized transportation facilities and motorized facilities.

There is a critical need to develop a new multi-functional barrier system complying with the specific requirements needed for the accommodation of vehicles, pedestrians and cyclists; one that is affordable from a constructability and installation standpoint; one that is appealing from an aesthetic perspective; one that takes into consideration adequate and proper sight distance, and one that is designed to safely contain and redirect direct hits from non-motorized users. The ultimate objective of this proposed research is to develop a barrier system that considers the safety of motorists, pedestrians, and bicycles while satisfying the Proposed Right-of-Way Accessibility Guidelines (PROWAG) and the American Association of State Highway Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH) Test Level 3 requirements.

Objective:

This project would seek to investigate the geometric and design requirements needed to develop and appropriately evaluate a multi-functional barrier system that safely accommodates motorists, pedestrians and cyclists on roadways that serve multiple modes of transportation.

Benefits:

At locations where proper lateral offset cannot be provided due to Right-of-Way limitations or other constraints, a positive protection device is needed to protect bicyclists and pedestrians from motorized vehicles. A combination traffic-pedestrian-bicycle concrete barrier rail is currently the only option available for this purpose. From a cost-benefit perspective, however, a concrete combination barrier does not represent a viable solution, given the high construction and installation costs.

There is an urgent need to design a new multi-functional guardrail system complying with the specific requirements needed for the accommodation of vehicles, pedestrians and cyclists, while satisfying PROWAG and MASH Test Level 3 requirements. This project will provide the opportunity to investigate the needed geometric and design requirements necessary in the development and evaluation of a barrier system that accommodates multimodal accessibility. The intended result of this research project would be to deliver a new cost-effective roadside barrier system that is designed to safely accommodate motorized and non-motorized users.

Related Research:

Back in late 1990s, with the passing of the Transportation Equity Act for the 21st Century (TEA-21), the Federal Highway Administration (FHWA) adopted a policy to create an integrated, intermodal transportation system that improves safety and accessibility for bicyclists and pedestrians and provides travelers with a real choice of transportation modes (Lewendon et. al., 2004). According to the policy, all new and improved transportation facilities should be planned, designed, and constructed giving consideration to the presence and safety of non-motorized users.

Over the last few decades, AASHTO has worked towards accomplishing this goal by establishing committees that are looking at the safety from the perspective of non-motorized road users. Unfortunately, a discrepancy in recommended rail height originated from the different perspectives between bicycle facility designers and bridge designers. The AASHTO “Bridge Specifications” and “Guide for the Development of Bicycle Facilities” require a 54-inch and a 42-inch bicycle railing height on bridges, respectively (AASHTO, 1999; AASHTO, 1989). Later studies determined that there was no existing empirical data to support the selection of either height for bicycle railing and that structures constructed with 42-inch pedestrian railing height did not affect non-motorized user’s safety. The AASHTO Bridges and Structures Subcommittee, however, preferred maintaining the 54-inch railing height specification for railing placed on shared path bridge facilities to adequately protect the public.

Existing guidelines for the design of railing for bicyclists were reviewed as part of NCHRP 20-7 (168) project (Lewendon et. al., 2004). Within this project, the authors reported of known guidelines at the federal, international, state and local levels. The 1989 AASHTO “Standard Specifications for Highway Bridges” serves to help the designer with the proper bridge railing selection based on the type of traffic that is anticipated on the bridge (AASHTO, 1989). The guideline, however, does not include criteria outlining the choice of a specific railing type. It only recommends the installation of a combination railing when the need arises for protecting pedestrians and bicyclists. With the 2002 AASHTO “Standard Specifications for Highway Bridges”, specific requirements for railing height started being imposed (AASHTO, 2002). With this document, the AASHTO guidelines for 54-inch and 42-inch railing height became requirements when selecting barriers to protect non-motorized users. This document also required specific size limits in the openings between horizontal and vertical elements of a combination bridge rail system to prevent objects from falling or being pushed through the railing (AASHTO, 2002). Specific geometric requirements for design of guardrails and handrails are also reported by the American with Disability Act (ADA), which ensures access to the built environment for people with disabilities.

The NCHRP 20-7 (168) project also reviewed European and foreign guidelines for the adoption of bicycle railing heights (Lewendon et. al., 2004). As a result of this review, it was reported that foreign Countries have different guidelines for bicycle railing heights, which span from 47 inches in Denmark to 59 inches for bridge locations in England.

Based on their extensive literature review and outreach results, the NCHRP 20-7 (168) study recommended a minimum bicycle railing height of 48 inches in locations where bicyclists need to be protected from severe hazards. This bicycle railing height has been recommended in other instances when the edge of the travel lane is laterally offset less than 5 feet from the edge of the non-motorized facility in order to prevent bicyclists from falling over the railing and into the path of oncoming traffic.

There are a variety of research studies currently in development to address unresolved questions regarding geometric and safety requirements for multi-modal facilities. These studies, however, are more targeted to either propose updates on existing AASHTO guidelines from a geometric perspective, or to investigate planning, design, and operational issues when considering pedestrian and bicyclists. No known research or testing studies currently involve the investigation of pedestrians and bicyclists’ safety through a much needed development of a roadside barrier design that safely accommodates vehicles and non-motorized users on a multi-modal facility.

Tasks:

The following tasks are proposed:

a. Conduct a literature review of documented national and international research regarding the investigation and adoption of bicycle and pedestrian rail heights;

b. Survey State Department of Transportation personnel and international transportation agencies to determine current practices, as well as related needs and concerns regarding combination railing systems;

c. Determine available relevant crash data sources to complement needed information;

d. Develop a guardrail system design to accommodate motorists, pedestrians, and cyclists;

e. Construct, full-scale crash test and evaluate the proposed system to MASH Test Level 3 requirements;

f. Develop criteria for placement and use of an appropriate combination traffic-pedestrian -bicycle railing height;

g. Suggest proper aesthetically pleasant system terminal option(s) for design and evaluation in future study.

Implementation:

The intended result of this research project would be to deliver a new cost-effective roadside barrier system that is designed to safely accommodate motorized and non-motorized users.

Sponsoring Committee:AFB20, Roadside Safety Design
Research Period:24 - 36 months
Research Priority:Medium
RNS Developer:Ali R. Hangul and Chiara Silvestri Dobrovolny
Source Info:AFB20 Summer Meeting 2017
Date Posted:01/03/2018
Date Modified:01/05/2018
Index Terms:Barriers (Roads), Design, Highway facilities for nonmotorized users, Pedestrian safety, Pedestrians, Bicycles, Right of way (Traffic), Barrier separated lanes, Complete streets,
Cosponsoring Committees: 
Subjects    
Highways
Pedestrians and Bicyclists
Design
Safety and Human Factors

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