Requirements for the location, number, dimensions, signs, and other aspects of accessible parking spaces are established by laws, such as the Americans with Disabilities Act (ADA), so that facilities are readily accessible and usable by people with disabilities.
For most businesses and state or local government facilities, parking accessibility rules are determined by the 2010 ADA Standards for Accessible Design (2010 Standards).
All new construction projects and, usually, alterations are expected to adhere to minimum accessibility requirements. Existing facilities may have more leniency in removing barriers.
Private businesses that fall under the scope of Title III of the ADA as public accommodations are required to remove barriers when the undertaking is "readily achievable," per the 2010 Standards. "Readily achievable" is defined in the ADA as meaning "easily accomplishable and able to be carried out without much difficult or expense."
When a business restripes parking spaces, they must adhere to the 2010 Standards.
The 2010 ADA Standards include a "safe harbor" for path of travel compliance:
If a public entity has constructed or altered required elements of a path of travel in accordance with the specifications in either the 1991 Standards or the Uniform Federal Accessibility Standards before March 15, 2012, the public entity is not required to retrofit such elements to reflect incremental changes in the 2010 Standards solely because of an alteration to a primary function area served by that path of travel.