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VII. Proposed Improvements of Moving Deformable Barrier Test

This NPRM proposes to require use of an improved 50th percentile male dummy (the ES-2re) in the MDB test in place of the SID and would take advantage of the enhanced injury assessment capabilities of the dummy by specifying injury criteria consistent with those developed for the dummy. These criteria are the same ones proposed above for the vehicle-to-pole test. Comments are requested on using the SID-H3 dummy in the test.

This NPRM would also maintain the current FMVSS No. 214 applicability of the MDB test to LTVs with a GVWR of 2,722 kg (6,000 lb) or less. [51]  At this time, we do not believe that applying the MDB test to LTVs with a GVWR over 2,722 kg (6,000 lb) would provide safety benefits to occupants of these heavier vehicles, yet it would add test burdens. However, while LTVs with a GVWR over 6,000 lb would continue to be excluded from the MDB requirements, today's proposed pole test would apply to LTVs with a GVWR of up to 4,536 kg (10,000 lb). The pole test is a more stringent test of the thorax of occupants of heavier struck LTVs than the MDB test and would result in reduced chest injuries.

With regard to thoracic injury criteria, some vehicles that now meet the MDB test in FMVSS No. 214 when tested with the SID might exceed the proposed rib deflection limit when tested with the ES-2re dummy and so might need to be redesigned. NHTSA’s 1999 Report to Congress (Status of NHTSA Plan for Side Impact Regulation Harmonization and Upgrade, March 1999) showed that 3 of 8 FMVSS No. 214 compliant vehicles exceeded the European 42 mm (1.65 inch) rib deflection limit in tests performed according to the EU 96/27/EC side impact test procedures. (The EU 96/27/EC specifies the use of the EuroSID-1 dummy, a different barrier, a different angle of impact and different injury criteria.)  Since the proposed ES-2 dummy is more sensitive than the EuroSID-1 dummy to thoracic impact forces, more vehicles would have likely exceeded the rib deflection limit in the aforesaid European side impact tests if the ES-2 dummy had been used. Additionally, the lateral velocity component of the FMVSS No. 214 MDB is roughly equivalent to the 50 km/h (30 mph) impact velocity specified in the EU 96/27/EC, but the U.S. MDB is much heavier and stiffer than the European barrier. Judging from these facts, NHTSA believes that some U.S. vehicles might not comply with the proposed upper limits of 44 mm (1.73 inch) upper limit for rib deflection and/or the 2,800 N (629 pound) upper limit for abdominal force criterion without redesign, if the ES-2re dummy were used in FMVSS No. 214 MDB side impact tests. Based on test results of certain vehicles, the agency has tentatively concluded that it is feasible to meet the proposed requirements.

The agency has conducted FMVSS No. 214 crash tests using the ES-2re and MDBs of various configurations and weights moving at various impact speeds. These tests are discussed in detail in the ES-2 Technical Report that has been placed in the docket. Two FMVSS No. 214 MDB tests were conducted using the test procedures specified in the standard and the ES-2re in the driver and rear passenger seating positions. Test results are tabulated below in Tables 8 and 9 for tests of the dummy in the driver and rear passenger positions, respectively.


Table 8. FMVSS No. 214 MDB Test Results
(ES-2re Driver)
Test Vehicle Restraint HPS
and/or SIAB
HIC36 Rib-Def.
(mm)
Lower Spine
(gs)
Abd.-Force
(N)
Pubic-Force
(N)
Proposed Limits   1,000 35-44 82 2,400-2,800 6,000
2001 Ford Focus None 137 36 60 1,648 2,833
2002 Chevrolet Impala None 69 46 49 1,225 1,789

Table 9. FMVSS No. 214 MDB Test Results
(ES-2re Rear Passenger)
Test Vehicle Restraint HPS
and/or SIAB
HIC36 Rib-Def.
(mm)
Lower Spine
(gs)
Abd.-Force
(N)
Pubic-Force
(N)
Proposed Limits   1,000 35-44 82 2,400-2,800 6,000
2001 Ford Focus None 174 20 59 1,121 2,759
2002 Chevrolet Impala None 187 12 58 4,409 2,784

Tables 8 and 9 show that the 2001 Ford Focus would meet the proposed FMVSS No. 214 MDB test requirements when it is tested with the ES-2re dummy (using the injury criteria associated with that dummy). The Ford Focus is a small car. The task is generally easier for large vehicles with a high ride height. The test results of the Ford Focus indicate that an upgraded MDB test using the ES-2re dummy with its associated injury criteria would be practicable.

The test results also show that the 2002 Chevrolet Impala would not comply with all of the proposed FMVSS No. 214 MDB test requirements. It did not meet the 44 mm (1.73 in) rib deflection criterion for the driver dummy (45.6 mm). Also, the abdominal force of the rear seat dummy exceeds the 2,500 N (562 pounds) limit by a large margin. An examination of the passenger compartment interior reveals that the rear armrest design and its location might be the problem. The armrest is made of foam material and its main portion is approximately 75 mm (3 inch) in width, 75 mm (3 inch) in height, and 250 mm (12 inch) in length. The lower edge of the armrest is approximately 100 mm (4 inches) above the seat surface. During a MDB side impact test, the protruded armrest would contact the abdominal area of a 50th percentile male dummy that is placed in the rear outboard seating position on the struck side. A severe abdominal impact is likely to create an excessively large force resulting in injuries. Since the SID dummy does not measure the abdominal force, this potential injury risk would not be detected in the existing FMVSS No. 214 MDB test. The use of ES-2re dummy in the MDB test would identify this.

It seems evident that the armrest of the Chevrolet Impala can be modified to mitigate this situation. A common modification is to extend the lower edge of the armrest to completely cover the lower torso of the test dummy. This design has already been used in many vehicles, including the 2001 Ford Focus. It is noted that this particular modification might reduce the rear seat width by a small amount.


This NPRM also proposes to upgrade the MDB requirements of FMVSS No. 214 by requiring vehicles to comply when tested with the 5th percentile female dummy (SID-IIsFRG). As noted above in this preamble, NASS data show that nearly 35 percent of MAIS 3 and greater side impact injuries occurred to occupants represented by the SID-IIsFRG dummy (5 foot 4 inches and under). The small stature occupant suffered relatively more head and abdominal injuries and relatively fewer chest injuries. These data indicate a safety need for an injury assessment tool representing small stature occupants to supplement the 50th percentile male dummy specified in the MDB test. [52]  The agency proposes that the criteria proposed for the SID-IIsFRG in the vehicle-to-pole test must also be met in the MDB test with the SID-IIsFRG.

Another proposed change to the MDB test in FMVSS No. 214 concerns the provision in S3(b) that excludes passenger car rear seats that are too small to accommodate the SID. The provision would be amended to specify that the seats would be excluded only if they cannot accommodate the SID-IIsFRG. If the seat cannot accommodate the mid-size male dummy but is able to fit the SID-IIsFRG, the seat would not be excluded from the MDB test. Further, the determination as to whether an ES-2re (or a SID-IIsFRG) can be accommodated in the rear seat would be made when using either the ES-2re or the SID-IIsFRG in the driver’s seating position. When the SID-IIsFRG is used in the driver's seating position, the driver's seat would be positioned full forward. Adjustable rear seats would be placed in their most rearward, full down position when seating the male or female dummy.

The technical report for the SID-IIsFRG dummy that accompanies this NPRM discusses the crash tests that the agency has conducted using this dummy. Several aspects of those tests are discussed below.

NHTSA tested the Ford Focus and Chevolet Impala to FMVSS No. 214’s MDB test procedure using the SID-IIsFRG in the driver and rear passenger seating positions. Test results are tabulated below in Tables 10 and 11.


Table 10. FMVSS No. 214 MDB Test Results
(SID-IIsFRG Driver)
Test Vehicle Restraint HPS
and/or SIAB
HIC36 Lower Spine
(g)
Pelvis (N)
Proposed Limits   1,000 82 5,100
2001 Ford Focus None 181 72 5,621
2002 Chevrolet Impala None 76 52 2,753
2001 Buick Le Sabre Thorax 130 67 4,672

Table 11. FMVSS No. 214 MDB Test Results
(SID-IIsFRG Rear Passenger)
Test Vehicle Restraint HPS
and/or SIAB
HIC36 Lower Spine
(g)
Pelvis (N)
Proposed Limits   1,000 82 5,100
2001 Ford Focus None    526 65 3,997
2002 Chev Impala None    153 89 5,711
2001 Buick Le Sabre None    221 77 4,041 (preliminary)

Tables 10 and 11 show that the 2001 Ford Focus would almost fully comply with the proposed FMVSS No. 214 MDB test requirements when tested with the SID-IIsFRG dummy and its associated injury criteria. Only the pelvis force for the driver dummy was exceeded in this test, which, judging from the film coverage, could be attributed to the intruding armrest. [53]  Alternatively, the 2002 Chevrolet Impala was able to meet all of the driver injury criteria with at least a 37 percent margin. The 2001 Buick Le Sabre also met all the proposed criteria for the driver dummy.

The 2002 Chevrolet Impala was the only vehicle that would not comply with the proposed rear seat FMVSS No. 214 MDB test requirements, since both the lower spine acceleration and the pelvis force of the rear seat dummy exceeded the proposed injury limits. As discussed previously, the rear armrest design might be the problem, and a simple remedy appears to be technically feasible.



[51] LTVs with a GVWR over 6,000 lb were excluded from the MDB requirements because they could meet the MDB requirements prior to the extension of the requirements to LTVs.

[52] As noted in an earlier footnote, IIHS is using the SID-IIs in its MDB test. Two SID-IIs test dummies are positioned on the struck side of the test vehicle, one in the driver seat and one in the seat behind the driver. The tests are conducted with a 1,500 kilogram (3,300 pound) MDB with a 90 degree impact.

[53] A copy of the film is available from the FHWA/NHTSA National Crash Analysis Center Film Library, 20101 Academic Way, Suite 203, Ashburn, VA 20147-2604. Telephone: 703-726-8236; Fax: 703-726-8358.

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