Interpretation ID: 7556
Chief Representative
Emissions & Safety
Isuzu Technical Center of America, Inc.
46401 Commerce Center Drive
Plymouth, MI 48170
Dear Mr. Odaira:
This responds to your letter asking about the side door strength test procedures of Standard No. 214, Side Impact Protection, as they apply to a certain pickup truck design. You described three alternative methods of fixing the vehicle in position and asked whether they are consistent with the standard's test procedure.
By way of background information, the National Highway Traffic Safety Administration does not provide approvals of motor vehicles or motor vehicle equipment. Under the National Traffic and Motor Vehicle Safety Act, it is the responsibility of the manufacturer to ensure that its vehicles and equipment meet applicable requirements. The following represents our opinion based on the facts provided in your letter.
S4(a) of Standard No. 214 sets forth the following procedures for fixing a vehicle in position for the quasi-static side door strength test:
Place the sill of the side of the vehicle opposite to the side being tested against a rigid unyielding vertical surface. Fix the vehicle rigidly in position by means of tiedown attachments located at or forward of the front wheel centerline and at or rearward of the rear wheel centerline. (Emphasis added.)
The side door strength test is then conducted by applying a loading device to the outer surface of the door, until the loading device travels 18 inches. See S4(d).
You asked about these procedures in connection with a certain pickup truck design, which can be described as follows. The cab of the truck is attached to the frame by means of flexible rubber mountings. The rear body is installed separately on the frame. The cab of the truck is over the front wheels, and the rear body is over the rear wheels.
You requested our comments on three alternative methods of testing the pickup truck at issue. The first would involve fixing the frame of the vehicle at or forward of, and at or rearward of, the front and real wheel centerlines. You stated, however, that the rear portion of the cab would not be rigidly fixed by this method, and that the application of the Standard No. 214 loading device would result in the stretching of the cab's rubber mountings and upward tilting of the cab as a whole.
Your second alternative would involve adding a third fixing of the vehicle, in addition to the front and rear fixings of Alternative 1. This additional fixing would be at the rear of the cab, on both sides. You indicated that this would permit the side door strength test to be conducted without tilting the vehicle, but that the relative cab to frame fixing would not be the same as on an actual vehicle.
Your third alternative would involve fixing the cab alone to a test fixture, at three locations. You stated that a problem with this method may be that the cab itself, and not the vehicle, is tested.
In considering how the Standard No. 214 quasi-static test should be conducted for a particular vehicle, it is important to bear in mind that the purpose of the test is to measure the crush resistance of a side door. The agency is not measuring the extent to which a vehicle's suspension or other design features permit the vehicle to tilt when specified loads are applied. In order to measure the crush resistance of a door in a test, it is necessary that the vehicle be fixed rigidly in position. Otherwise, the application of a load to the side door could simply result in movement of the vehicle as a whole.
Standard No. 214's test procedure was developed initially for cars. As noted by your letter, the combination of tying the vehicle down at or forward of, and at or rearward of, the front and rear wheel centerlines and placing the sill of the side of the vehicle opposite to the side being tested against a rigid unyielding vertical surface is sufficient to rigidly fix a passenger car in position for test purposes. Your letter raises the issue of how the Standard No. 214 test should be conducted if the specified procedure does not result in a particular vehicle, such as one with a divided body, being rigidly fixed in position.
For purposes of compliance testing, NHTSA would take the following actions. First, the agency would examine whether the procedure set forth in S4(a) would result in the vehicle being rigidly fixed in position. This could involve considering various tiedown arrangements within the areas specified by S4(a). If the agency determined that the procedure was not sufficient to rigidly fix a vehicle in position, e.g., the entire cab of a pickup truck would tilt upward during a test, it would then follow the specified procedure but also add an additional tiedown attachment as necessary to rigidly fix the vehicle in position. In making this additional attachment, the agency would take care to ensure that the attachment did not interfere with the side door strength test.
I can offer the following comments on the three alternative test methods you described. NHTSA would not follow the Alternative 1 test procedure since the vehicle would not be rigidly fixed in position under that procedure. The agency would also not follow the Alternative 3 test procedure since it does not include one of the tiedown arrangements specified by S4(a). The agency might follow an approach along the lines of Alternative 2, assuming that it determined that the S4(a) procedure was not sufficient to rigidly fix the vehicle in position.
I hope you find this information helpful. If you have any other questions, please contact Edward Glancy of my staff at this address or by phone at (202) 366-2992.
Sincerely,
Paul Jackson Rice Chief Counsel
ref:214 d:10/5/92