(a) The purpose of this part is to provide a means by which manufacturers of motor vehicles may obtain temporary exemptions from Federal motor vehicle safety standards on the basis of substantial economic hardship, facilitation of the development of new motor vehicle safety or low-emission engine features, or existence of an equivalent overall level of motor vehicle safety.

(b) The purpose of this part is also to provide a means by which manufacturers of passenger motor vehicles may obtain a temporary exemption from compliance with all or part of a Federal bumper standard issued under part 581 of this chapter on a basis similar to that provided for exemptions from the Federal motor vehicle safety standards.