Interpretation ID: nht74-3.19
DATE: 11/12/74
FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA
TO: The Flxible Company
TITLE: FMVSS INTERPRETATION
TEXT: This responds to Flxible's October 11, 1974, petition to exempt the "trackless trolley coach" category of bus from the requirements of Standard No. 121, Air brake systems. You describe the vehicle as similar to your diesel bus but without the weight of the diesel engine, and with electrodynamic braking provided by the traction motor to a maximum of 2.0 mph per second in conjunction with brake operation.
I have enclosed a copy of our letter to Flyer Industries Limited on the same subject. The letter describes our position with regard to status of the trackless trolley as a motor vehicle, and also how it must be tested under Standard No. 121.
You have noted several difficulties in testing a vehicle which uses overhead electric lines as a source of power. I would like to point out that, as we interpret the National Traffic and Motor Vehicle Safety Act of 1966, we have established the policy that a manufacturer may conduct certification testing in any manner it chooses, as long as it is calculated, in the exercise of due care, to demonstrate that the vehicle would pass if tested as specified in the standard. Thus, you would be free to certify the vehicle based on tests without use of overhead lines and the benefit of electrodynamic braking. We understand from your letter that without the weight of the diesel engine the trackless trolley has better braking performance than the equivalent diesel engine.
At this time we have issued a proposal that would establish special test conditions for certain vehicles and limited exemptions for other vehicles, based on their configuration. We will consider your letter as a petition under this rulemaking action, and we invite you to make further comments to Docket 74-10; Notice 7, within the next 30 days.
We will advise you of our determination by letter or by notice in the Federal Register.
YOURS TRULY,
ENCLS.
THE Flxible CO.
OCTOBER 11, 1974
Mr. Richard Dyson, Acting Chief Counsel National Highway Traffic Safety Administration 400 7th. Street S.W. Washington, D.C. 20590
Dear Mr. Dyson: The purpose of this letter is to request a clarification concerning the certification of a trackless trolley coach to Federal Motor Vehicle Safety Standard #121, Braking System.
The Flxible Company is seeking certification of the trackless trolley coach without testing as a part of our family of vehicle of which the diesel powered buses are certified to FMVSS #121.
The trackless trolley coach will be on a forty (40) feet long by one hundred two (102) inches wide chassis. All brake system components, with the exception of the air compressor are the same ones used on the diesel coach. The air compressor, of necessity, is motor driven and of larger capacity than the compressor used on most diesel coach applications. Calculations, based on compressor capacity and reservoir volume, show that the compressor exceeds the requirements of Para. S5.1.1 of FMVSS #121 by 55-60 per cent.
While the chassis is the same as the diesel coach, the total vehicle weight will be slightly less than a diesel coach, powers by a V-8 diesel engine, due to component weight. The weight reduction is a plus factor in meeting the stopping distances as outlined in Table 11 of FMVSS #121.
In addition, electrodynamic braking will be provided by the traction motor to a maximum of 2.0 mile per hour per second (MPHPS) in conjunction with brake operation. This feature will most certainly aid the overall braking performance of the vehicle
One very important point must be made in requesting certification of the trackless trolley coach without testing. There is no test track available with 600 VDC overhead lines with which to run the vehicle. Cost for such an installation would be prohibitive especially considering the very limited use. Testing methods, such as a portable power system, would also be expensive and not at all practical due to the physical size and weight of components to produce 600 VDC at 550 amperes
Based on the above information, The Flxible Company requests deletion of testing and granting of certification to FMVSS #121 of the trackless trolley coach.
STANLEY C. FRYE -- Product Engineer-Advanced Design