vehicle safety standards. (3) Timely consideration of applications The Secretary shall approve or reject a vehicle modifier plan not later than 1 year after receiving an application from a stretch limousine alterer. (e) Definitions In this section: (1) Incomplete vehicle The term incomplete vehicle has the meaning given such term in section 567.3 of title 49, Code of Federal Regulations. (2) Stretch limousine The term stretch limousine means a new or used passenger motor vehicle that has been altered in a manner that increases the overall wheelbase of the vehicle, exceeding the original equipment manufacturer’s wheelbase dimension for the base model and year of the vehicle, in any amount sufficient to accommodate additional passengers with a seating capacity of not fewer than 9 passengers including the driver. (3) Stretch limousine alterer The term stretch limousine alterer means a person who alters by addition, substitution, or removal of components (other than readily attachable components) an incomplete vehicle or a certified passenger motor vehicle before or after the first purchase of the vehicle to produce a stretch limousine. (4) Passenger motor vehicle The term passenger motor vehicle has the meaning given that term in section 32101. . (b) Enforcement Section 30165(a)(1) of title 49, United States Code, is amended by inserting 30129, after 30127, . 5. Stretch limousine crashworthiness (a) Research Not later than 4 years after the date of enactment, the Secretary shall complete research into side impact protection, roof crush resistance, and air bag systems for the protection of occupants in stretch limousines given alternative seating positions or interior configurations, including perimeter seating arrangements. (b) Research requirements In conducting the research required under subsection (a), the Secretary shall— (1) develop one or more tests to evaluate side impact protection, roof crush resistance, and air bag systems of stretch limousines