49 CFR Parts 37 & 38 - Department of Transportation (DOT) ADA Regulations

(c) Requests for modification of a public entity's policies and practices may be denied only on one or more of the following grounds:

(1) Granting the request would fundamentally alter the nature of the entity's services, programs, or activities;

(2) Granting the request would create a direct threat to the health or safety of others;

(3) Without the requested modification, the individual with a disability is able to fully use the entity's services, programs, or activities for their intended purpose.