There is an excellent blog by the owner of a woman-owned car dealership in California at AskPatty.com "Automotive Advice for Women". She supports and is the president of the United Spinal Association and her blog posts include many that relate to disabled drivers.
29 January 2008 International Organization for Standardization press release
A new ISO standard for spinal disc implants will help reduce suffering of back pain patients. The new standard will help ensure that spinal disc prostheses meet requirements for wear resistance, particularly important as once implanted these will need to absorb the impact from the body’s daily activities for years to come.
Medical surgery ISO 18192-1:2008 Implants for Surgery – Wear of Total Intervertebral Spinal Disc Prostheses – Part 1: Loading and Displacement Parameters for Wear Testing and Corresponding Environmental Conditions for Test [Withdrawn]
The primary users of this ISO standard will be medical device manufacturers and laboratories in public and private sectors, providing biomechanical testing services for medical devices. The estimated worldwide market size for artificial disc prostheses will exceed USD 1 billion by the year 2010.
The standard was replaced by ISO 18192-1:2011 Updated