One intention of the 1990 Americans with Disabilities Act (ADA) was to increase access to public facilities for people with disabilities. Many disabled people require modifications to their vehicles. The National Highway Traffic Safety Administration (NHTSA) is interested in estimating how many vehicles have been adapted for transporting disabled persons. NHTSA is also interested in the safety of these vehicles.

In its December 1997 Research Note, "Estimating the Number of Vehicles Adapted for Use by Persons with Disabilities," NHTSA addressed several questions about vehicles used by persons with disabilities.

The research note began with statistics about disabled Americans:

• By the end of 1994, the Census Bureau estimated that 54 million noninstitutionalized Americans had a disability; 9.9 percent of those had a severe disability.

• The Census Bureau estimated in 1995 that 26.1 percent of disabled people between the ages of 21 and 64 were employed, or about 3.7 million people.

• The Census Bureau estimated that 25.9 percent of the 2.3 million long-term users of mobility equipment (e.g., wheelchairs, canes, and walker crutches) in the 21-to-64 age group were employed, or almost 600,000 people.

Most modifications for people with disabilities are made "aftermarket," or after the person purchases a vehicle from the manufacturer. The motor vehicle modification and adaptive equipment industry commands a small portion of the automobile market. Most businesses involved are also small. Some are "alterers" (manufacturers of vehicles certified to Federal Motor Vehicle Safety Standards), and others are manufacturers of adaptive equipment and aftermarket vehicle modifiers.

Three manufacturers--Ford, Chrysler, and General Motors offer reimbursements to vehicle owners for a portion of the cost of adaptive equipment.

Occupational therapists, specialized driver trainers, and vocational rehabilitation specialists advise the adaptive equipment modification businesses on the equipment and modifications necessary to meet disabled persons' needs.

Seeking to answer questions about the number of modified vehicles being used by persons with disabilities, NHTSA's National Center for Statistics and Analysis (NCSA) analyzed data from several sources. NCSA reported:

• Approximately 211,000 people with disabilities use some type of adaptive equipment with their vehicles.

• According to the Census Bureau's 1992 Truck Use Survey, approximately 184,000 trucks operate with some type of modification.

NHTSA's National Automotive Sampling System Crashworthiness Data System (NASS/CDS) showed that from 1995-1996 almost two-tenths of one percent of vehicles "in tow-away crashes were found to have some type of adaptive driving equipment (hand controls, steering controls, joy-stick steering)." A statistical test performed for independence between single-vehicle crashes and the presence of adaptive equipment found no evidence of any association, allowing the assumption that "vehicles with adaptive equipment are neither over nor under represented in crashes."

A comparison of the percent of vehicles involved in tow-away crashes to the total number of motor vehicle registrations (1995) provided an estimate that 382,907 vehicles in the U.S. have some type of adaptive equipment.

NHTSA expects the number of vehicles with adaptive equipment will continue to increase for two reasons: (1) the average age of the population is increasing and (2) recreation opportunities continue to improve for people with disabilities. NHTSA plans continued study of this issue.

Questions about this research should be directed to Ellen Hertz at 202-366-5360 or Gayle Dalrymple at 202-366-5559. You can also review information on vehicle adaptions and other traffic safety issues online at http://nhtsa.dot.gov/people/ncsa or http://nhtsa.dot.cars/rules/adaptive.