Engineering Lab Helping Ensure Safety Of Small Buses

ScienceDaily (Oct. 17, 2007) — Paratransit buses, or the smaller buses, are a fairly common sight on the roads of most American communities. Public transit and social service agencies, among others, often use the 16- to 20-seat vehicles to provide access to public transportation for people with disabilities in support of the Americans with Disabilities Act of 1990.

The paratransit bus industry in the U.S. follows strict regulations, including all applicable Federal Motor Vehicle Safety Standards. Most of these standards apply to electrical, lighting, and Gross Vehicle Weight Ratings. These standards are very important, yet they do not examine the crashworthiness of these buses during side impact and rollover accidents. Fortunately, in Florida, a partnership between Florida State University, the Center for Urban Transportation Research at the University of South Florida and the Florida Department of Transportation is working to improve the safety of those who depend on paratransit buses for transportation.

Jerry Wekezer, a distinguished university professor specializing in civil engineering, and Robert Westbrook, a nationally recognized innovator in the field of bus mechanics and design, have been leading this effort since 1999. They have studied several different bus designs and construction materials. The overarching factor is to determine their ability to survive a side impact or rollover accident with minimal harm to occupants.

Every year, the Florida Department of Transportation buys more than 300 paratransit buses for local transportation providers across the state, Westbrook said. Because there are no mandated standards related to dynamic rollover and side impact, the FDOT seeks to do everything it can to make sure the vehicles are safe before putting them on the road.

At the Florida A&M University-Florida State University College of Engineering, Wekezer has established a Crashworthiness and Impact Analysis Laboratory using federal and state transportation funds. Engineering researchers perform finite element studies and laboratory tests on individual vehicle components to determine how well they stand up to various types of dynamic impact. Members of the engineering team, including undergraduates to postdoctoral research associates, with the support of the Center for Urban Transportation Researchís technical team, develop complex computer models to determine how well specific types of paratransit buses will perform in collisions.

It would be very expensive to obtain actual paratransit buses for crashworthiness and rollover testing a single bus can cost more than $70,000, Wekezer said. So what we have done with the lab is develop methods for testing specific components, such as side panels and connections to determine how they respond to loads that simulate a side-impact collisions. The data collected from these tests then are applied to validate finite element models used for a comprehensive crashworthiness and safety assessment of these buses.

Finite element modeling is a computational process in which a three-dimensional object is developed in order to make very specific predictions as to how the vehicle will be affected by a variety of impact conditions. In the case of paratransit buses, the current models consist of more than a half-million individual pieces or elements.

Finite element analysis is a sophisticated tool that enables us to predict how a vehicle will perform under adverse conditions, Wekezer said. ìIt also allows us to share our findings with the manufacturers so thy can take steps to remediate any problems that we find. For example, a problem that we occasionally see is weak connections between the side wall and the roof or floor supports. Sometimes a simple fix, such as placing additional bots at key connection points, is all that is needed to make a vehicle sufficiently crashworthy. The manufacturer would much rather make an inexpensive fix like this than have to do an in-depth analysis into the design of its bus.

Although dynamic rollover and side impact standards for paratransit buses are not yet mandated in the U.S., the project team has been instrumental in their development and implementation. The Florida Department of Transportation is currently implementing these performance standards in all of their vehicle procurement contracts. Also, Wekezer is leading a group under the auspices of the United Nations Economic Commission for Europe, which is charged with developing a revised European standard for crash and safety assessment of small buses. These bus safety rules now apply to all 27 member states of the European Union as well as 44 members of the U.N. (excluding the United States).

taken from

Adapted from materials provided by Florida State University.


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