Interpretation ID: aiam4798
Inc. 1203 Woodbridge Avenue Ann Arbor
MI 48105;
Dear Mr. Kadoya: This responds to your request for interpretations o several safety standards and the Bumper Standard, in connection with a planned 'active' suspension system. I regret the delay in responding to your letter. Your questions are responded to below. By way of background information, the National Highway Traffic Safety Administration (NHTSA) does not provide approvals of motor vehicles or motor vehicle equipment. Under the statutes administered by this agency, it is the responsibility of the manufacturer to ensure that its vehicles and equipment comply with applicable standards. The following represents our opinion based on the facts provided in your letter. According to your letter, Mazda is concerned about the protocol of compliance testing of vehicles equipped with an active suspension system. This concern arises because many standards do not specify a suspension height that is to be used during compliance testing. As you noted, this has not been a concern for conventional suspension systems, since they do not provide for variable height. NOTE: THIS IS PART II OF AN INTERPRETATION LETTER TOO LONG TO BE ACCEPTED INTO THE DATABASE AS IS. PART I COVERS COMPLIANCE ISSUES (PART 571), AND STANDARDS 108, 211 AND 204. ITS KEY NUMBER IS 5023. Standard No. 208, Occupant Crash Protection In asking about Standard No. 208, you stated the following: Section S8.1.1.(d), 'Vehicle test attitude,' specifies the test procedure for determining the vehicle test attitude that is to be used for testing. Specifically, this section requires that the vehicle's pretest attitude, '...shall be equal to either the as delivered or fully loaded attitude or between the as delivered and fully loaded attitude.' The as delivered attitude is defined by S8.1.1(d) as being, '...the distance between a level surface and a standard reference point on the test vehicle's body, directly above each wheel opening, when the vehicle is in its 'as delivered' condition. The 'as delivered' condition is the vehicle as received at the test site...' Because it is highly likely that the test vehicle will not have been operated for a period of days prior to arriving at the test site, the suspension height may have fallen by 'y' mm. The fully loaded attitude is defined as the attitude of the vehicle when loaded in accordance with S8.1.1(a) or (b) and a determination of the height of the suspension at the fully loaded condition is made from the same level surface, using the same standard reference points, as were used to determine the 'as delivered' condition. The definition of the 'as delivered' condition is quite clear. However, Mazda interprets the 'fully loaded condition' of the vehicle to be the condition when the vehicle's ignition is 'on.' In this instance it is likely that the height of the standard reference points on the vehicles body when in the 'fully loaded condition' relative to the level surface will be greater than for the 'as delivered' condition. Conversely, conventional vehicle suspension systems will likely have an 'as delivered' height greater than the 'full loaded' height. However, this fact is of no importance as S8.1.1(d) states that the pretest vehicle attitude may be, '...between the as delivered and the fully loaded attitude.' With respect to the injury criteria specified by section S6 of this standard, Mazda's interpretation is that these criteria must be met with the vehicle's ignition in the 'on' position only. You then asked three questions, (1) whether Mazda's interpretation of the definition of the 'fully loaded condition' is correct with respect to the condition of the ignition switch, (2) whether Mazda's interpretation of the irrelevance of the relative relationship between the 'as delivered' and 'fully loaded' conditions is correct, and (3) whether Mazda's interpretation of the meaning of 'between the as delivered and the fully loaded attitude' is correct. In addressing you questions, I will begin by noting that Standard No. 208 specifies occupant protection requirements which must be met in specified crash tests at any impact speed up to and including 30 mph. While the standard specifies a number of test conditions, it does not specify suspension height. However, the standard does specify vehicle attitude, which is closely related to suspension height. In addressing how Standard No. 208 applies in the absence of a specification for vehicle height, the relationship between the standard's attitude specification and vehicle height must be considered. Section S8.1.1(d) specifies the attitude of the vehicle during testing, i.e., the angle of the vehicle relative to the ground. This test condition ensures that the vehicle is not overly tilted toward the front or back, or to one side. The section accomplishes this purpose by specifying that, during a compliance test, the height of the vehicle at each wheel is within a specified range. This range, which may be somewhat different for each wheel, is determined by looking at the vehicle in the 'as delivered' condition an the 'fully loaded' condition. A vehicle must meet the requirements of Standard No. 208 when its height at each wheel is anywhere within the specified ranges. On first glance, one might read section S8.1.1(d) to create a height requirement, since ranges of height are determined under that section (at each wheel). This would be incorrect, except in a very narrow sense, since Standard No. 208 does not specify, for vehicles with variable height suspension systems, what suspension height should be used in the two conditions ('as delivered' and 'fully loaded') where the specified ranges of height are determined under section S8.1.1(d). Looking at the Standard No. 208 as a whole, we believe it is clear that NHTSA explicitly decided to limit the standard's evaluation of occupant crash protection in frontal impacts to how vehicles perform in impacts of 30 mph or less, even though the requirements also have relevance at higher speeds. It is our interpretation that the frontal crash test requirements need to be met at all suspension heights that can occur at speeds of 30 mph or less, with the vehicle operational. It is also our interpretation that the crash test requirements need to be met only at suspension heights that can occur at the speed used in the crash test. A remaining issue is how section S8.1.1(d) applies for vehicles with variable height suspension systems. As discussed below, vehicle attitude should be determined under this section using the actual suspension setting (or equivalent, if the setting is automatic) to be used in a crash test. For purposes of illustration, I will assume a vehicle with two very different suspension height settings. It would not be appropriate to conclude that the ranges of height determined under section S8.1.1(d) should simultaneously cover both suspension heights. Such ranges would be very large, and would not ensure that the vehicle is not overly tilted toward the front or back, or to one side. Moreover, such ranges would not be relevant to the real world, with respect to vehicle attitude. Traditional vehicles can be viewed as having a single suspension 'setting.' This single suspension condition is used in determining vehicle attitude under section S5.8.8.1. The ranges of height result from the differences in loading under the 'as delivered' and 'fully loaded' conditions. A single suspension 'setting' (or equivalent, if the setting is automatic) should similarly be used in determining vehicle attitude for vehicles with variable height suspension systems. The 'setting' should be the one to be used in a crash test. With respect to Mazda's question concerning means of maintaining intended suspension height for compliance testing, please see our discussion provided with respect to Standard No. 111. You also asked for an interpretation of section S8.2.7 of Standard No. 208. That section specifies additional conditions to be used for lateral moving barrier crash testing. Section S8.2.7(a) states that the vehicle is at rest in its 'normal attitude.' You stated that Mazda interprets the meaning of 'normal attitude' to be that vehicle attitude which is intended when the vehicle's ignition is in the 'on' condition, with the vehicle loaded pursuant to S8.1.1(a) or (b), and while the vehicle is at rest. Standard No. 208 provides manufacturers the option of either equipping their vehicles with safety belts or meeting certain alternative requirements, including lateral moving barrier crash test requirements. These requirements are relevant at all vehicle heights that can occur during vehicle operation, regardless of speed. Moreover, NHTSA has not decided to limit the standard's evaluation of this aspect of safety performance to how vehicles perform at certain limited speeds. It is our interpretation that the lateral moving barrier crash test requirements, if applicable, must be met at all suspension heights that can occur with the vehicle operational. 'Normal attitude' is the attitude determined under section S8.1.1(d). As discussed above, attitude for vehicles equipped with variable height suspension systems is determined under section S8.1.1.(d) using the actual suspension setting (or equivalent, if the setting is automatic) to be used in a crash test. Standards No. 212, Windshield Mounting, No. 219, Windshield Zone Intrusion, No. 301, Fuel System Integrity In asking about Standards NO. 212, No. 219, and No. 301, you noted that NHTSA has previously issued an interpretation to Mazda about how these standards apply to adjustable height suspension systems. In a letter dated August 10, 1982, the agency addressed a vehicle equipped with a suspension system having two height positions, one for normal highway driving and another for off-road driving, which could be selected by the driver. NHTSA stated the following: Safety Standards No. 212, No. 219, and No. 301 do not specify a height adjustment because almost all vehicles have a single, set adjustment . . . . After careful consideration, it is the agency's position that such a vehicle capable of variable height adjustment would have to comply with the vehicle adjusted to any position that is possible. This is true because the vehicle could be driven on the highway, for example, even if it were adjusted to the off-road position. Consequently, it is important that the vehicle comply with the standards in all positions. You noted that while suspension height could be adjusted by the driver for the system discussed in the agency's previous interpretation, the active suspension system you are currently considering would use an on-board electronic controller to select suspension height, and suspension height would not be adjustable by the driver. Consequently, according to your letter, only one unique set of suspension height parameters is possible for a given vehicle speed and loading condition as is the case with conventional suspension systems. You stated that because it is possible to determine exactly what the intended suspension height should be for a given situation, it is Mazda's opinion that the test vehicle should be tested at the intended suspension height given the specified speed and loading conditions. You also stated that , using an 'intended purpose' argument, Mazda concludes that the requirements of the three standards are to be met only when the vehicle's ignition is 'on.' You then asked whether these suggested interpretations are correct. Standard No. 212 specifies windshield retention requirements that must be met in a specified frontal crash test at any impact speed up to and including 30 mph. Similarly, Standard No. 219 specifies windshield zone intrusion requirements that must be met in a specified frontal crash test at any impact speed up to and including 30 mph. Standard No. 301 specifies fuel system integrity requirements for several specified crash tests. These include a frontal crash test similar to those in Standards No. 212 and No. 219. Requirements for this test must be met at any impact speed up to and including 30 mph. Other tests include a rear moving barrier crash test, a lateral moving barrier crash test, and a static rollover test. We agree that the requirements of Standards No. 212, No. 219, and No. 301 need not be met for vehicle heights that only occur when the engine is not on, since the requirements are only relevant is situations where the vehicle is operating. Looking at the three standards as a whole, were believe it is clear that, for the frontal tests specified by the three standards, NHTSA decided to limit the standards' evaluation of safety performance to how vehicles perform in impacts of 30 mph or less, even thought the requirements have relevance at higher speeds. It is our interpretation that the frontal crash test requirements specified by these standards need to be met at all suspension heights that can occur at speeds of 30 mph or less, with the vehicle operational. It is also our interpretation that the crash test requirements need to be met only at suspension heights that can occur at the speed used in the crash test. We reach a different conclusion for Standard No. 301's other crash test requirements. These requirements are relevant at all vehicle speeds and suspension heights. Moreover, NHTSA has not decided to limit the standard's evaluation of these aspects of safety performance to how vehicles perform at certain limited speeds. It is our interpretation that these crash test requirements must be met at all suspension heights that can occur with the vehicle operational. Part 581 Bumper Standard In asking about the Part 581 Bumper Standard, you noted that NHTSA has previously issued several interpretations of how the standard applies to vehicles with adjustable height suspension systems. In a letter to Subaru dated May 6, 1986, NHTSA stated the following: Given the absence of a specific test condition concerning suspension height, it is our interpretation that a vehicle must be capable of meeting the standard's damage criteria at any height position to which the suspension can be adjusted. There is no language in the test requirements of the standard limiting their applicability to 'the manufacturer's nominal design highway adjusted height position.' This interpretation is consistent with the purpose of the Bumper Standard, set forth in section 581.2, to reduce physical damage to the front and rear ends of a passenger motor vehicle from low speed collisions. If a vehicle's suspension could be adjusted so that its bumper height resulted in bumper mismatch with other vehicles in the event of low speed collision, the reduction in physical damage attributable to the Bumper Standard would be defeated in whole or part. In another letter, dated February 12, 1985, NHTSA stated that a vehicle is 'required to meet the pendulum test of Part 581 in any vehicle use scenario in which the vehicle operates, and the barrier test of Part 581 when the engine is idling.' You suggested , for the barrier test, that the agency's May 1986 interpretation may be inappropriate for your active suspension system, since your system provides for only one suspension height when the engine is idling. You also suggested, for the pendulum test, that these interpretations seem to be in conflict with the Bumper Standard's stated purpose to reduce physical damage to motor vehicles in low speed collisions. We assume that you are referring to the fact that your suspension system has heights that occur only at speeds greater than 35 mph. You then requested that NHTSA provide an interpretation of Part 581 with respect to your system. In addressing how Part 581 applies to vehicles equipped with an active suspension system, I will address separately the standard's barrier and pendulum tests. For the barrier test, a vehicle must meet specified damage criteria after an impact into a fixed barrier that is perpendicular to the line of travel of the vehicle, at 2.5 mph. Section 581.6 sets forth conditions applicable to bumper testing. Under section 581.6(c), at the onset of a barrier impact, the vehicle's engine is operating at idling speed. Looking at the Bumper Standard as a whole, we believe it is clear that NHTSA decided to limit the barrier test's evaluation of bumper performance to how vehicles perform in 2.5 mph frontal impacts, event though the requirements have relevance at lower and higher speeds and when the vehicle is nonoperational. It is our interpretation that the barrier test requirements specified by this standard need to be met at all suspension heights that can occur at 2.5 mph. We reach a different conclusion for the pendulum test, which serves the purpose of creating a bumper height requirement. This requirement is relevant at all vehicle speeds and suspension heights, and when the vehicle is nonoperational. I note that while Mazda is correct that the Bumper Standard's stated purpose is to reduce physical damage to motor vehicles in low speed collision, NHTSA has justified the bumper height requirement on safety concerns related to 'higher speed collisions.' In proposing Standard No. 215, the predecessor of Part 581, the agency stated: . . . in higher speed collisions the tendency of a bumper to override another or to ride under or over a guardrail creates hazards for vehicle occupants. Vehicles with interlocking bumpers block traffic and expose their occupant to considerable danger, particularly if they attempt to get out to unlock bumpers. By overriding or underriding a guardrail, a bumper may strike a supporting post, or similar fixed object, with serious consequences for the vehicle and its occupants. 35 FR 17999, November 24, 1970. The relevance of the bumper height requirement to nonoperational situations is also clear, e.g., to help protect parked cars. Moreover, NHTSA has not decided to limit the bumper height requirements to how vehicles perform at certain limited speeds. It is our interpretation that the pendulum test requirements must be met at all suspension heights that can occur, regardless of vehicle speed or whether the ignition is turned on. This interpretation is consistent with an October 18, 1978 letter to Nissan, in which NHTSA addressed how the pendulum test applies to vehicles equipped with height control systems, including automatic height control systems. Among other things, the agency stated the following: . . . There is no language in the pendulum test requirements of the standard which would limit their applicability to only the ignition-on or ignition-off situation or to the recommended driving position for normal roadways. The vehicle must be capable of meeting the pendulum test requirements at all stable bumper heights possible at unloaded vehicle weight. Thus, in the situations described in Question 1 and 2 of your letter, in which an automatic height control system is employed, the vehicle must comply with the pendulum test requirements in both the ignition-on and ignition-off positions . . . . I note that one of our past letters, a December 24, 1984 letter addressed to Porsche, appears to suggest that the pendulum test must be met in any setting in which the system operates 'when the engine is idling.' This might be read to suggest that the pendulum test need not be met when the vehicle is nonoperational. However, this interpretation cited section 581.6(c) in concluding that the engine is idling during Part 581 testing. Section 581.6(c) applies only to the barrier test and not the pendulum test. We therefore consider this interpretation to be incorrect to the extent that it is inconsistent with the analysis presented above. Sincerely, Paul Jackson Rice Chief Counsel;