Transportation Deployment Casebook/2014/Bus Accessibility

This article discusses the lifecycle of bus accessibility in the United States. Specifically, it looks at the accommodation of mobility aids such as wheelchairs from the mid 1900s to the present. It includes a description and history of accessibility technology, regulations that affected the technologies, and an analysis of the implementation of wheelchair lifts and ramps on transit buses.

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Qualitative AnalysisEdit

Mode DescriptionEdit

Accessibility technology in buses has increased as a result of the need to accommodate the growing disabled population in the U.S. and the need to comply with disability regulations. Innovations have included bus lifts, ramps, air suspension (‘kneeling’ buses), and, to a lesser degree, universal design ideas that lower the floor of the bus while raising the height of the bus stop. Regulations have also affected entrance height, priority seating, handrails, fare boxes, stop requests levers, and signage. Choosing between which mobility technology to implement depends on the environment in which the transportation entity operates, existing infrastructure, and nature of the regulation. Each of these innovations has advantages and disadvantages.


A disability, as defined by the Americans with Disabilities Act (ADA), is an “impairment that substantially limits one or more major life activities a history of having such an impairment, or being regarded as having such an impairment [1].

The wheelchair is a mobility aid belonging to any class of three or four-wheeled aids, that is usable indoors and designed for and used by individuals with mobility limitations [2]. These aids can also include scooters, Segways, and child strollers. This report will look specifically at technology involved in accommodating wheelchairs and other mobility aids on buses.

In general, accessible buses make for an effortless entrance when boarding the bus and include wide enough doorways, wide enough interior walkways, and space for wheelchairs and other mobility aids to sit during the ride. Additionally, interior fixtures exist to keep mobility aids secure while the vehicle is moving and destination displays have been designed to accommodate physically and visually impaired.

A wheelchair lift (platform lift) is a fully powered device designed to raise a wheelchair and its occupant in order to rise above a step or other vertical barrier. The innovation brought together existing technologies of hydraulic lifts and buses by creating a lift that fit the size of a bus entrance and allow for storage while the bus is in operation. Wheelchair lifts can also be installed in homes or businesses and are often added to both private and public vehicles in order to meet accessibility requirements laid out by the ADA. Today, wheelchair lifts are required to have hand railings, barriers to prevent any of the wheels of a wheelchair or mobility aid from rolling off the platform during its operation, and storage requirements while the bus is in motion.

A ramp is a movable platform that can be used to roll a mobility aid on board. The ramp has similar regulations to the lift regarding size, stowage, movement, barriers, and surfaces and additionally requires a slope of no more than 1:48. Air suspension buses (‘kneeling’ buses) use air-adjustable suspension to lower the entire bus towards the ground. By lowering the bus, drivers create a shorter (if any) step for riders to get on. After riders are on, the bus will be raised back up in order to once again continue moving.

A low-floor bus refers to a bus that is accessible from a certain minimum height of step from ground level. Low-floor buses have no steps at least one of the entrances and part or all of the interior walkways.

Platform-level boarding elevates the bus stop to the same level at which riders enter the bus so that they avoid taking a large (if any) step to get on the bus. Plat-level boarding is commonly used in rail transport and Bus Rapid Transit (BRT) services. Platform-level boarding can be used in combination with other bus accessibility measures to create a universal design which benefits all users.

The SceneEdit

Throughout history, community attitudes and physical barriers in the built environment have prevented people with disabilities from fully participating in society. Along with the growth in the disabled population, the quest for independence and equal rights has grown, as well. At the beginning of the 20th century, the average human lifespan was only 47 years, and people who received spinal cord injuries had only a 10% chance of survival [3]. Two World Wars created a huge population of veterans with disabilities, and the advancement of antibiotics and other medicines enabled people to survive accidents and illnesses which were previously fatal. As a result, the number of people with mobility issues increased and continues to increase today, relative the overall population. Innovations related to accessibility came about in mid 1900s as result of need accommodate both able-bodied and disabled people on transit vehicles and, towards the end of the 1900s, new disability regulations.

Despite legislative requirements for accommodation, people with disabilities face barriers to physical activity, both in the built and social environments [4]. The challenge facing the disabled is the absence of flexibility since they are considered an afterthought [5]. The trend towards suburban living multiplies the problem since many communities became more dependent on cars and less dependent on transit. Cars were a large barrier towards movement since they require motor and mental skills as well as capital. The decrease in demand for transit and increase in demand for cars transformed the landscape by worsening transit service for those who depend on it [5]. Additionally, people with disabilities are sensitive to problems with street design and barriers to mobility [6]. The built environment has a greater effect on mobility disability for those with lower extremity impairment.


Walter Harris Callow (1896-1958) was a Canadian veteran who invented the accessibility bus in 1947 [7]. He started by having two custom made buses built in Pubnico, Nova Scotia for veterans returning from WW2 and others in wheelchairs [8]. The back of the buses had a hydraulic ramp, which is lowered to allow the wheelchairs to come aboard easily [8]. The wheelchairs used in the buses were specially designed by Callow and were adaptable to the patient's needs. They were locked down into position to minimize movement while the bus was in operation. He later garnered the support of General Motors and Ford to mass produce the wheelchair coaches.

Early Market DevelopmentEdit

Transportation entities avoided implementing accessibility technology on a mass scale until regulations were put into place. Even though the technology was available, disabled people with mobility needs only made up a minority of the market. People with disabilities are able to overcome barriers, but required additional expenditure of resources to do so. Although only a marginal group, a vocal number people with disabilities were demanding more accessibility on public transit and winning. The Paralyzed Veterans of America, National Paraplegia Foundation, and Richard Heddinger filed suit in 1970 against the Washington Metropolitan Area Transit Authority, asking them to incorporate accessibility into their design of a new subway system in Washington, D.C [9]. Their victory was a landmark in the struggle for accessible public transit.

However, the regulations regarding the requirements of accessibility were still unsettled. In Lloyd v. Regional Transportation Authority, 548 F. 2d 1277 (1977), the U.S. Court of Appeals, Seventh Circuit ruled that individuals have a right to sue under Section 504 of the Rehabilitation Act of 1973 and that public transit authorities must provide accessible service [9]. However, in Snowden v. Birmingham Jefferson County Transit Authority, The U.S. Court of Appeals undermined this decision by ruling that authorities need to provide access only to handicapped persons other than those confined to wheelchairs [9].

The Role of Policy in Birthing PhaseEdit

In 1970, the Urban Mass Transportation Act became law, and required all new American mass transit vehicles be equipped with wheelchair lifts but the American public Transit Association (APTA) delayed implementation for 20 years [9]. In 1983, the Americans Disabled for Accessible Public Transit (ADAPT) organization was established as a grassroots United States disability rights organization with an initial goal to get wheelchair accessible lifts on buses. Throughout the 1980s, their campaign for bus lifts expanded to the entirety of the U.S. and became known for immobilizing buses to draw attention to the need for lifts. APTA was forced to protect operators who cannot afford lifts and stated that lifts were a local matter [4].

The American Disability Act (ADA) of 1990 is a civil rights law that prohibits discrimination based on disability and the regulation that ordered for accessibility nationwide. Title II of the ADA covers public transportation services, such as city buses and public rail transit and prohibits disability discrimination by all public entities at the local and state level [1]. Public transportation authority’s cannot discriminate against people with disabilities and must comply with requirements for accessibility in newly purchased vehicles. According to the ADA, mobility aids cannot exceed 30 inches in width and 48 inches in length when measured two inches above the ground (with the exception of Segways). Aditionally, service will not be provided if the combined weight of the rider and the wheelchair exceeds 600 pounds. New buses ordered on or after August 26, 1990, must be accessible to individuals with disabilities.

The Growth of the ModeEdit

The ADA was a major milestone in the effort to foster inclusion of people with disabilities into the broader society both through transportation and other means. The ADA established guidelines for how the built environment should be modified in ways so that the participation of all people may be maximized [4]. When the ADA was passed, a major concern was retrofitting buses with to accommodate wheelchairs. Buses traditionally had steps leading from the ground to the level where passengers sit. The number of Americans with disabilities increased 25 percent between 1990 and 2000 both as a result of growing understanding of what defines a disability and the growth in overall population [10].

Development during the Mature PhaseEdit

Today, the disability for ages 18-64 is nearly 20 million and for over 65 is nearly 15 million [10]. Nearly 80% of the population now lives past the age of 65 [2]. Approximately 56.7 million people of the 303.9 million in the civilian population had a disability in 2010 and about 38.3 million people (12.6 percent) had a severe disability [11].

An increasing number of buses use low-floor design and optionally also 'kneel' air suspension and have electrically or hydraulically extended beneath-floor ramps to provide level access for mobility aid users and people with baby carriages. Prior to more general use of such technology, these wheelchair users could only use specialist paratransit mobility buses. People with disabilities are often at risk of isolation if they live in communities that rely solely on automobile transportation. Because of our greater understanding of some of the difficulties that disabled people face, we have passed regulations that better allow for access. The ADA has a uniform nationwide mandate that ensures accessibility regardless of local attitudes.

On Friday, July 23, 2010, Attorney General Eric Holder signed final regulations revising the Department's ADA regulations, including its ADA Standards for Accessible Design. Amendments included regulations stating that the controls of lifts and ramps shall be interlocked with the vehicle brakes, transmission, or door, or shall provide other appropriate mechanisms or systems, to ensure that the vehicle cannot be moved when the lift is not stowed. Additional regulations regarding boarding aid size, stowage, movement, barriers, and surfaces are included in updated federal regulations.

Lock-in and ReinventionEdit

The ADA lift and ramp-equipped bus are the ones most used in the U.S. and certainly have room for reinvention. Universal design assists those who need assistance while benefiting others. The intent of universal design is to simplify life for everyone by making products, communications, and the built environment more usable by as many people as possible at little or no extra cost. Universal design for bus accessibility uses a low-floor bus and an elevated-level platform so that wheelchairs could roll onto the vehicle like at a subway [5]. . This would also help others who can walk but have difficulty with stairs as well as people who use mobility aids. Low-floor buses are increasingly being sued but the raising of the ground at bus stops has not occurred to high extent in the U.S.

Autonomous vehicles might also be a solution to the needs of disable travelers. The physical and mental abilities of the driver are no longer a factor in ensuring a safe trip since disadvantaged travelers could simply instruct the vehicle where to go [5]. Whatever the solution may be, a well-designed built environment should aim to reduce or eliminate accessibility issues that disadvantaged people have rather than reinforcing them.

Quantitative AnalysisEdit

Using ADA transit bus statistics from the U.S. Department of Transportation, Federal Transit Administration, National Transit Summaries and Trends (Washington, Annual Issues), I found the number ADA lift and ramp-equipped transit buses from 1993-2011. Then, I predicted the amount of buses to be expected in a given year using the logistic equation



S(t) Number of ADA Lift and Ramp-Equipped Buses
t Time in years
t0 is the inflection time
K Saturation of ADA Equipped Buses
Regression Results
K = 78000
b = 0.22866
t0 = 1995.748
Adjusted R Square = 0.977364

ADA Equipped Buses

The S-curve predicts the data very well with an R-squared value of .977. The black line represents the inflection time of when the growth beings to slow. Unfortunately, data could not be found prior to the implementation of the ADA.

Stage Period
Birthing stage 1970 - 1984
Growth stage 1984 - 2001
Maturity stage 2001 - present

The S-curve is used to identify the birth, growth and maturity stages. The table above show the approximate life cycle stages of ADA equipped buses in the U.S. Growth is estimated to have occurred starting in 1984 and continued until around 2001. Though the ADA was not put into place until 1990, it certainly sped up the growth even though the growth stage begun to occur in the mid 1980s. The changing point (t0) from when growth slows to decline is around 1995.


  1. a b Information and Technical Assistance on the Americans with Disabilities Act. ADA, n.d. Web. 04 Nov. 2014. <>.
  2. a b " Accessibility." Metro Transit. 2014. Web. 04 Nov. 2014. <>.
  3. "UNIVERSAL DESIGN HISTORY." The Center for Universal Design. 2008.Web. 5 November 2014 <>.
  4. a b c Lopez, Russ. "Vulnerable Populations." The Built Environment and Public Health. San Francisco: Jossey-Bass, 2012. N. pag. Print.
  5. a b c d Garrison, William L., and David M. Levinson. "Recapitalization." The Transportation Experience: Policy, Planning, and Deployment. New York: Oxford UP, 2006. 325-335. Print.
  6. Clarke, P., et al. "Mobility Disability and the Urban Built Environment." American Journal of Epidemiology 168.5 (2008): 506-13. Web.
  7. Willick, Frances. "Wheelchair Bus Service Turns 65; Founder Lauded." The Chronicle Herald. 29 July 2012. Web. 05 Nov. 2014. <>.
  8. a b "Wheelchair Bus Takes Veterans to Exhibition." Ottawa Citizen - Google News Archive Search (23 Aug. 1950): 4. Ottawa Citizen - Google News Archive Search. Web. 5 November 2014. <,1549248>.
  9. a b c d Pelka, Fred. ABC-CLIO Companion to The Disability Rights Movement. Santa Barbara: ABC-CLIO, 1997. Disability Rights and Independent Living Movement. University of California, Berkeley, 2004. Web. 04 Nov. 2014. <>.
  10. a b "United States Census Bureau." American Community Survey. N.p., 2012. Web. 06 Nov. 2014. <>.
  11. Brault, Matthew W. "Americans With Disabilities: 2010." US Census Bureau. July 2012.Web. 5 November 2014 <>.