Factors in Transit Bus Ramp Slope and Wheelchair-Seated Passenger Safety

By Craig Smalley and Karen Bertocci, University of Louisville, Department of Bioengineering

Nearly 3 million U.S. adults are wheelchair or scooter users1, and as the population ages this number is expected to rise. Many wheelchair users rely upon public transportation to access work, medical care, school and social activities. Annual wheelchair boardings on public transit buses vary across the U.S., ranging from 10,00013,000 boardings per year in a medium size city such as Louisville, Ky., to an average of 20,000 boardings in larger cities such as Philadelphia2, while major cities such as New York City, estimate over 600,000 wheelchair passenger boardings per year3.

In collaboration with the Transit Authority of River City (TARC), we have been studying wheelchair accessibility on public transit buses as part of a National Institute of Disability and Rehabilitation Research project. Our goal is to identify remediable factors that contribute to increased safety and independence for wheelchair-seated passengers and to propose solutions that benefit all stakeholders.

In our previous research, we found that wheelchair users experienced more difficulties and potentially injurious incidents while boarding or alighting the bus using the wheelchair ramp than during transit, and that steep slope was a common factor in these incidents4,5. Because no published information on actual transit bus ramp slopes exists, we set out to measure ramp slopes in situ in order to identify factors affecting ramp slope and to assess how varying ramp slopes affect the ability of wheelchair users to board and exit the bus independently and without incident.

Ramp slopes were measured over a 15-month period using an inclinometer embedded in the ramp of a Gillig, 2008 model, low-floor transit bus. This equipment was synchronized with data from video cameras mounted inside the bus that recorded each wheelchair boarding/alighting. Data from over 400 wheelchair trips was collected and analyzed. Average ramp slope was 4.3 degrees, however ramp slopes as high as 15.5 degrees were measured, exceeding the proposed ADA maximum-allowable ramp slope of 9.5 degrees6.

During boarding, the proposed ADA maximum allowable ramp slope was exceeded in 66.7% of ramp deployments to street level, and in 1.9% of ramp deployments to sidewalk level. During alighting, the proposed ADA maximum allowable slope was exceeded in 56.8% of ramp deployments to street level and in 1.4% of ramp deployments to sidewalk level. Steep ramp slopes created difficulties for wheelchair users. When the ramp slope was 10 degrees or steeper, wheelchair users were 3 times more likely to require assistance when boarding or alighting, and nearly 5 times more likely to encounter an incident. Our observations indicated two main factors that contributed to wheelchair users increased need for assistance and greater likelihood of an experiencing an incident during boarding/alighting.

The first factor was where the bus operator deployed the ramp either to street level or sidewalk level. Ramps deployed to street level resulted in an average ramp slope nearly 7 degrees steeper than ramps deployed to sidewalks. We observed several instances when bus drivers deployed the ramp to street level instead of pulling closer to the sidewalk curb or utilizing a nearby sidewalk (ex. at the opposite side of an intersection). Furthermore, ramps were not always deployed in a location allowing for a direct approach free of obstacles.

The second factor was the degree to which the bus operator kneeled the vehicle. In our study, fully kneeling the bus reduced ramp slope by approximately 5 degrees, yet we observed the bus being fully kneeled in just 1 of 6 ramp deployments; and kneeled less than 50% in 1 of 4 ramp deployments despite the relatively level terrain in the Louisville metropolitan area. If a wheelchair user cant independently traverse the ramp and requests assistance, the bus operator is required to leave his/her seat and provide assistance. Bus operators must often assist in pushing or pulling wheelchairs up ramps or past obstacles, causing schedule delays and putting operators at increased risk of injury.

Issues related to the built environment can also affect ramp slope. Sidewalks typically slope towards the street to promote drainage. A ramp deployed from a bus that is stopped in close proximity to the sidewalk will result in the end of the ramp resting on the sidewalk at a higher elevation compared to a ramp deployed from a bus stopped farther from the sidewalk. Additionally, cross-slopping streets and sidewalks can present challenges to wheelchair users during boarding/alighting.

The results of this study indicate a need for greater awareness on the part of transit agencies and bus operators regarding actions that can be taken to mitigate unnecessarily steep ramp slopes. Training and empowering bus operators to take proactive steps to improve wheelchair passenger safety and independence during boarding and alighting may reduce incidents and injuries as well as schedule delays. Additionally, urban planners should anticipate the effects of bus stop design and terrain on ramp deployment.

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Factors in Transit Bus Ramp Slope and Wheelchair-Seated Passenger Safety