Interpretation ID: aiam1722
Engineering Department
Todco Division
2195 Alpine Way
Hayward
CA 94545;
Dear Mr. Wigand: This responds to your November 17, 1974, letter asking whether trailer converter dolly which may also be coupled to a two-axle truck-tractor as a 'third axle attachment' (the Jifflox) must be equipped with a spring brake parking system to conform to the requirements of Standard No. 121, *Air brake systems.*; Our November 4, 1974, response (copy enclosed) to your September 27 1974, questions on the same subject states that the Jifflox would be exempt from parking brake requirements if it is manufactured and sold for use as a trailer converter dolly. A trailer converter dolly is defined in 49 CFR 571.3 as a trailer equipped with one or more axles, a lower half of a fifth wheel, and a drawbar.; You questioned our conclusion of November 4, 1974, that a truck-tracto which is manufactured to accept the Jifflox must be certified by its manufacturer as complying with the standard with the Jifflox in place. You argue that the Jifflox is simply another towed vehicle which meets the requirements applicable to trailer converter dollies.; The NHTSA has established that a vehicle which is designed to accept a optional component must be capable of meeting all applicable standards with that component installed. Specifically, in response to inquiries from Volkswagen, the NHTSA stated that a vehicle designed to accept an air conditioner, must be capable of meeting barrier crash requirements with the weight of an air conditioner installed.; Similarly, a vehicle designed to accept certain components must b capable of meeting Standard No. 121 with those components attached. For example, a truck-tractor designed to accept a cargo box forward of the fifth wheel must be capable of meeting all requirements of Standard No. 121 with that cargo box in place.; It is even more important that a vehicle design which involve modification of the air lines to accept the Jifflox must be capable of meeting all requirements of the standard with the Jifflox attached. The Jifflox connections, for example, can affect the actuation and release times of the truck air brake system. Also, the added GAWR capabilities of two rear axles would affect the stopping capabilities of the truck-tractor loaded to GVWR. Other standards (e.g., Standard No. 108, *Lamps, reflective devices, and associated equipment*) could be affected by the addition of Jifflox.; Thus we would require manufacturers of truck-tractors that are designe to accept the Jiffloox to certify compliance with Jifflox attached. We noted in our November 4, 1974, letter that, if the truck manufacturer determines that parking brakes are required on the Jifflox axle to meet S5.6.1 or S5.6.2, those parking brakes would have to be applied by an energy source that is not affected by loss of air pressure or brake fluid pressure in the service brake system.; Yours truly, Richard B. Dyson, Acting Chief Counsel