28 CFR Part 35 Title II Notice of Proposed Rulemaking (NPRM) (published 2008)

(c) Development of policies permitting the use of other power-driven mobility devices.  A public entity shall establish policies to permit the use of other power-driven mobility devices by individuals with disabilities when it is reasonable to allow an individual with a disability to participate in a service, program, or activity.  Whether a modification is reasonable to allow the use of a class of power-driven mobility device by an individual with a disability in specific venues (e.g., parks, courthouses, office buildings, etc.) shall be determined based on:

(1) The dimensions, weight, and operating speed of the mobility device in relation to a wheelchair;

(2) The risk of potential harm to others by the operation of the mobility device;

(3) The risk of harm to the environment or natural or cultural resources or conflict with Federal land management laws and regulations; and

(4) The ability of the public entity to stow the mobility device when not in use, if requested by the user.