IV. Regulatory, Research and Technological Developments--—1990 to Present

a. 1990 Simulated Vehicle-to-Vehicle Test—Chest and Pelvic Injury Criteria

FMVSS No. 214 was amended in 1990 to include dynamic requirements to improve the crashworthiness of vehicles in vehicle-to-vehicle side impact collisions (55 FR 45722; October 30, 1990). The amendments added a dynamic side impact test regulating the level of crash forces that can be experienced by an occupant when seated in a vehicle struck in a side impact. The dynamic requirements focused on thoracic protection because contact between the thorax and the side interior had been a primary source of serious injuries and fatalities and because further work was needed on head protection countermeasures, head injury criterion and test dummies capable of measuring the potential for head injuries in a side impact crash. The requirements were phased-in for passenger cars, beginning in 1993. They were extended in 1995 (60 FR 38749; July 28, 1995) to LTVs with a GVWR of 2,722 kilograms (6,000 lb) or less manufactured on or after September 1, 1998.

b. 1995 Upper Interior Impact Protection Requirements

In 1995, NHTSA issued a final rule amending FMVSS No. 201, "Occupant protection in interior impact," to require passenger cars, and trucks, buses and multipurpose passenger vehicles with a gross vehicle weight rating of 4,536 kg (10,000 lb) or less, to provide protection when an occupant’s head strikes certain upper interior components, including pillars, side rails, headers, and the roof, during a crash. The amendments added procedures and performance requirements for a new in-vehicle test, which were phased in beginning in model year 1999.

c. 1996 First Inflatable Side Impact Protection Systems

Side impact air bags (SIABs) were first installed in Mercedes E-class cars and all Volvo passenger cars in model year (MY) 1996. In MY 1997, BMW, VW/Audi, Cadillac, Nissan, and Toyota chose to install SIABs in certain production car models. Since then, SIABs have become more commonly available in the nation’s passenger vehicles. [10]

In 1996, NHTSA published an advance notice of proposed rulemaking (ANPRM) to obtain information in evaluating dynamic head protection systems, such as ways of testing these systems to assure that they yield sufficient safety benefits to justify amending the new requirements of FMVSS No. 201 to permit their installation. (61 FR 9136; March 7, 1996.)

d. 1997 Report to Congress re Possibility of Harmonizing U.S. and European Vehicle-to-Vehicle Tests

On September 16, 1996, in Congressional Conference Report 104-785 for the Department of Transportation and Related Agencies' Appropriations Act for fiscal year 1997, the conferees directed NHTSA to study the differences between the U.S. and then-proposed European side impact regulations and to develop a plan for achieving harmonization of these regulations. In response to that directive, NHTSA submitted a side impact harmonization plan to Congress in April 1997 ("Report to Congress NHTSA Plan for Achieving Harmonization of the U.S. and European Side Impact Standards," April 1997, see docket NHTSA 1998-3935-1 of the Department’s Docket Management System). NHTSA said that it would determine the potential for international harmonization by:

  1. Analyzing past research and performing new tests to determine the relative safety benefits offered by each regulation.

  2. Coordinating with industry and other interested groups to establish consensus on the activities, eliminate duplication of work, and reduce cost.

  3. Determining if functional equivalence exists or can be established between the two requirements.

  4. Coordinating with the European Union (EU) to assess harmonization options and approaches.

With respect to the third step, we described how we would follow our functional equivalence process in determining whether FMVSS No. 214 and the modified European regulation are functionally equivalent (49 CFR part 553, Appendix B). This process is used to determine whether the vehicles or equipment manufactured under a foreign standard produce more or at least as many safety benefits as those produced by the vehicles or equipment manufactured under a similar U.S. standard.

e. 1997 Head Injury Protection Criteria and First Generation Side Impact Test Dummy Capable of Measuring Head Impact Forces

The Head Injury Criterion (HIC) for lateral impacts was developed in 1997, when the agency published an NPRM proposing to add an optional vehicle-to-pole side impact test to FMVSS No. 201. 62 FR 45202; August 26, 1997. An anthropomorphic test dummy that was capable of measuring crash forces to the head in a side impact was also developed in 1997. The SID-H3 dummy, specified in 49 CFR Part 572, Subpart M, is a SID dummy with a Hybrid III head/neck system. The Hybrid III head is instrumented with a tri-axial accelerometer package, positioned to measure the acceleration of the center of gravity. This permits the measurement of HIC. The SID-H3 dummy is currently used in the FMVSS No. 201 optional vehicle-to-pole test (see below) and in NHTSA’s New Car Assessment Program (NCAP) for side impact testing.

f. 1998 Pole Test to Evaluate Inflatable Side Impact Head Protection Systems

On August 4, 1998, NHTSA published a final rule amending the upper interior impact requirements of FMVSS No. 201, to permit, but not require, the installation of dynamically deploying upper interior head protection systems that were then being developed by some vehicle manufacturers to provide added head protection in lateral crashes (63 FR 41451). Compliance with the original upper interior impact requirements is tested at specified points called "target points."  Since compliance is often not practicable at target points located near the places where these dynamic systems are stored before they are deployed, vehicles equipped with the dynamic systems are allowed to meet alternative requirements at those points. These vehicles are also required to meet new requirements to ensure that these dynamic systems enhance safety. That final rule added procedures and performance requirements for testing the deployment of these systems and their protective capability through a combination of in-vehicle tests and a full-scale vehicle-to-pole crash test. In the crash test, the vehicle is propelled at a speed between 24 km/h (15 mph) and 29 km/h (18 mph) into a rigid pole at an angle of 90 degrees. (This NPRM refers to this FMVSS No. 201 pole test as the "29 km/h (18 mph)" pole test.) The pole is aimed at the head of a SID-H3 dummy seated in the front outboard seating position. The pole test injury criterion is HIC of 1000. (63 FR 41451; August 4, 1998.) 

g. Grant of 1998 Petition to Upgrade Side Impact Protection Standard

In July 1998, Advocates for Highway and Auto Safety (Advocates) submitted a petition for rulemaking requesting NHTSA to upgrade FMVSS No. 214 in several ways. First, Advocates contended that the injury criteria are not stringent enough, arguing that neither the occupants of passenger cars nor small LTVs are being provided adequate protection when their vehicles are struck by higher, heavier, and more aggressive LTVs. Second, they believed the MDB is not high/heavy enough because the barrier weight/height were originally designed to represent a vehicle fleet that was projected to be lighter and smaller than the current fleet. They stated that since 1988, the passenger car fleet has not changed significantly while the LTV fleet has grown in average weight and number. Third, they thought that EuroSID-1 has advantages to SID because of additional measurement capability. They recommended the following: amending FMVSS No. 214 to a higher safety performance level such that superior side impact air bags would be developed and installed in vehicles as standard equipment; replace the quasi-static door crush test with a side-to-pole impact test like that used under the recent FMVSS No. 201 upgrade; lastly, replace SID with Eurosid-1. The agency granted the petition because it believed that the side impact research activities it had planned would fully address the issues raised by the petition.

h. 1997-1999 NHTSA Research re Vehicle-to-Vehicle Test Harmonization

As a first step in assessing the functional equivalence of the U.S. and European side impact regulations, we tested vehicles that were certified to FMVSS No. 214 using the procedures and criteria of EU 96/27/EC (as modified, with a test dummy placed in the rear outboard seating position in addition to the front outboard position). The vehicles provided a range of marginal to good performers in FMVSS No. 214 tests and represented a wide range of manufacturers. The results indicated the ranking of the vehicles, according to compliance margin, when tested under EU 96/27/EC was not the same as when they were tested under FMVSS No. 214.

Additionally, a measurement anomaly in the European test dummy (EuroSID-1) related to the rib displacement was present in most, if not all, tests. This anomaly, along with the limited amount of comparative test data, did not allow a positive determination of functional equivalence of the two side impact regulations.

i. 1999-2000 Report to Congress and Response to Petition re Vehicle-to-Vehicle Test Harmonization

Based on our testing of eight vehicles that were certified to FMVSS No. 214 using the procedures and criteria of EU 96/27/EC, we informed Congress that we could not conclude from this set of testing whether vehicles designed to meet FMVSS No. 214 would meet the EU regulation. The agency also determined that the lighter and less stiff EU MDB was less representative of the current and future U.S. fleet than the current FMVSS No. 214 MBD, and that side impact countermeasures that would be based on the EU test might therefore not lead to enhanced real world safety. (See NHTSA’s report to Congress on the agency’s progress in assessing the functional equivalence of the two regulations: "Status of NHTSA Plan for Side Impact Regulation Harmonization and Upgrade, Report to Congress, March 1999," Docket NHTSA-98-3935-10.)

Also based on that testing, we denied most aspects of a 1997 petition for rulemaking from the Association of International Automobile Manufacturers (AIAM), the Insurance Institute for Highway Safety, and the American Automobile Manufacturers Association. These petitioners asked us first to determine that the dynamic side impact provisions of a European regulation (consisting of performance requirements, crash test barrier, test barrier face, and test procedures) are at least "functionally equivalent" to those in FMVSS No. 214. (65 FR 33508; May 24, 2000.)  Based on the assumption that that determination would be made, the petitioners then asked that we add the dynamic provisions of the European regulation to FMVSS No. 214 as a compliance alternative in the short run. Based on their belief that the European dynamic provisions are superior to those in FMVSS No. 214 in some respects, they also wanted us to replace the current dynamic provisions of FMVSS No. 214 with those of the European regulation (slightly modified) in the long run. In addition to our inability to determine that the European standard was at least functionally equivalent to FMVSS No. 214, we noted that the European barrier was less representative than the FMVSS No. 214 barrier of the side impact crash environment in this country.

However, we granted the portion of the petition requesting that we open a rulemaking proceeding to consider replacing the 50th percentile male side impact test dummy (SID) currently specified in FMVSS No. 214 with an improved version of the dummy (EuroSID-1) specified in the European regulation. We said that if the mechanical anomalies with EuroSID-1 could be solved, the greater measurement capabilities of the dummy would make its adoption attractive as a way of upgrading FMVSS No. 214. Thus, we said that our first steps would be to work with the Europeans to fix the dummy’s mechanical problems. Once that is accomplished, we would consider issuing a proposal to replace SID with the improved side impact dummy. We noted that adopting a more advanced test dummy means that we would also be considering the appropriate injury criteria to adopt with the dummy into our side impact protection standard. We said that if we eventually proposed to replace SID with an improved EuroSID-1, we might propose adopting the injury criteria now in EU 96/27/EC as well.

j. 2000-2003 NHTSA Research re Side Impact Dummies, Injury Criteria, and Crash Tests

In the 1999 Report to Congress, we outlined our side impact research plan for both harmonization and upgrade of FMVSS No. 214. Among other matters, the agency planned to improve the EuroSID-1 dummy to a new version, Eurosid-2 (ES-2), pursue incorporating a pole test using the ES-2 or SID-H3 dummy currently used in FMVSS No. 201’s optional pole test, and study the benefits and costs of side air bags and the possible risks to out-of-position occupants. Id., Appendix A.

NHTSA conducted or participated in extensive research following the research plan. We analyzed 1990-2001 crash data to determine characteristics of the occupants injured in near-side side impacts and how they were being injured, and to better understand the crash environment of vehicle-to-vehicle and narrow object side crashes, and found that head injuries and injuries to small statured occupants should be addressed. We fixed back-plate grabbing problems with the ES-2 dummy, [11] evaluated a 5th percentile female side impact dummy (SID-IIs, see later section) and made determinations as to the dummies’ suitability for crash testing. Injury criteria for occupant head, chest, abdomen and pelvis were also developed and/or evaluated. We conducted out-of-position testing of side air bags to assess risks of the SIABs to children. The agency also closely monitored the Insurance Institute for Highway Safety’s (IIHS’s) progress on developing that organization’s side impact moving barrier consumer information test program, and assessed the degree to which our and IIHS’s programs can best complement each other.

The results of these undertakings led us to decide to concentrate our efforts on improving head protection in side impacts by way of incorporating a pole test into FMVSS No. 214, with new test dummies capable of measuring head impact forces. An oblique (75 degree), 32 km/h (20 mph) crash test was developed. Full-scale oblique pole tests were conducted with the ES-2, SID-H3 and SID-IIs dummies, with injury assessment references values developed for the injury mechanisms measured by the dummies. "NHTSA Side Impact Research:  Motivation For Upgraded Test Procedures," Samaha, et al. (2003).

Full-scale side impact tests using a moving barrier were also conducted. These research projects were publicly presented in various forums, such as in a July 2002 NHTSA Research and Development Public Meeting [12] and in meetings of the International Harmonized Research Agenda (IHRA) Side Impact Working Group, and others.

k. Current Status of Second and Next Generation Side Impact Dummies

Today, there are new side impact dummies capable of measuring HIC in addition to the SID-H3 50th percentile male dummy. The ES-2 50th percentile male dummy has a well-developed biofidelic head with injury measurement capabilities. (The ES-2 has been modified with regard to rib extensions to address structural deficiencies identified by NHTSA in injury measurement of the chest in the dummy. The modified dummy, hereinafter referred to as "ES-2re," is described in detail later in this preamble.) There also is a test dummy representing a 5th percentile female, the SID-IIs, that is capable of measuring forces to the head, neck, shoulder, thorax, abdomen and pelvis body regions. In addition, a next-generation 50th percentile male side impact dummy, known as WorldSID, is under development by industry representatives from the U.S., Europe and Japan and the European and Japanese governments (see Docket No. 2000-17252). This future dummy is intended to better predict a wider range of injury potential in side impact testing than current dummies. However, the dummy is not yet available.

l. Industry Efforts to Improve Compatibility in Vehicle-to-Vehicle Crashes

In response to the NHTSA Administrator’s call for action to reduce the problem of vehicle incompatibility, some vehicle manufacturers have agreed to introduce changes to their LTVs to improve their compatibility in crashes with passenger cars. The Alliance of Automobile Manufacturers and IIHS announced a new voluntary industry commitment on December 4, 2003, to enhance occupant protection in front-to-side and front-to-front crashes. [13] The industry initiative consists of improvements and research made in several phases focusing on changes to improve the geometric mismatch between the frontal structures of LTVs and passenger cars, and on accelerating the installation of side impact air bags.

Under Phase 1 of the initiative concerning front-to-side crashes, manufacturers [14] have agreed that, not later than September 1, 2007, at least 50 percent of each manufacturer’s new passenger car and light truck (GVWR up to 8,500 lb) production intended for sale in the U.S. will be designed in accordance with either of the following head protection alternatives: (a) HIC36 performance of 1000 or less for a SID-H3 crash dummy in the driver’s seating position in an FMVSS No. 201 pole impact test, or (b) HIC15 performance of 779 or less (with no direct head contact with the barrier) for a SID-IIs crash dummy in the driver’s seating position in the IIHS MDB side impact crash test.

In Phase 2, not later than September 1, 2009, 100 percent of each manufacturer’s new passenger car and light truck (GVWR up to 8,500 lb) production will be designed in accordance with the IIHS MDB recommended practice of HIC15 performance of 779 or less for a SID-IIs crash dummy in the driver’s seating position. [15]

The agency welcomes these efforts. They are important and necessary first steps to reduce the problems associated with vehicle incompatibility. Voluntary efforts to equip vehicles with these new designs and life-saving devices will begin saving increased numbers of lives sooner than through the traditional regulatory approach and will reduce the cost of complying with government regulations.

The oblique pole test proposed by this NPRM would be phased-in over three years beginning approximately four years from the publication date of a final rule. This leadtime is proposed to give adequate time for manufacturers to plan for and design to specifications enabling their vehicles to meet an oblique test. Yet, if manufacturers began installing side impact air bags voluntarily on a widespread basis by 2007 with full implementation by 2009, we could see the fleet change years before implementation of the final rule. Many hundreds of lives could be saved in the near term.

The near term voluntary installation of side impact air bags would be a significant improvement to side crash protection. In the long term, installation of side air bag systems meeting our oblique pole test would take this improvement even further. The enhanced side impact air bags envisioned by this NPRM would save even more lives—hundreds more each year--than those saved by present technologies. Together, the industry’s near term voluntary initiatives and the agency’s long term regulatory solutions would address the side impact safety problem in a comprehensive and complementary way.

V. Existing Standard

FMVSS No. 214 specifies two types of performance requirements intended to protect the thoracic and pelvic regions of an occupant:  “quasi-static” requirements and “dynamic” requirements. They apply to passenger cars and to multipurpose passenger vehicles, trucks, and buses with a GVWR of 4,536 kg (10,000 lb) or less and 6,000 lb or less, respectively.

The quasi-static requirements limit the extent to which the side door structure of a vehicle is pushed into the passenger compartment during a side impact. The standard requires each side door to resist crush forces that are applied by a piston pressing a 300 mm (12 inch) steel cylinder against the door’s outer surface in a laboratory test. Since the requirement became effective in 1973, vehicle manufacturers have generally chosen to meet the requirement by reinforcing the side doors with metal beams.

The dynamic side impact test currently regulates the level of crash forces that can be experienced by an occupant's chest and pelvis when seated in a vehicle struck in a side impact. The dynamic requirements focus on thoracic pelvic protection because contact between the thorax and the side interior has been the primary source of serious injuries and fatalities.

The dynamic side impact test simulates a 90-degree intersection impact of a striking vehicle traveling 48 km/h (30 mph) into a target (i.e., test) vehicle traveling 24 km/h (15 mph). This is achieved by running a moving deformable barrier (MDB), which has all wheels rotated 27 degrees (crab angle) from the longitudinal axis, into the side of a stationary (test) vehicle at a 90-degree contact angle with a 54 km/h (33.5 mph) closing speed. At the initial contact, the longitudinal axes of the MDB and the test vehicle are perpendicular to each other. Two side impact dummies (SIDs) are used in the target vehicle. They are positioned on the struck side of the vehicle, one in the front seat with the other directly behind in the rear seat.

The MDB, which simulates the striking (i.e., bullet) vehicle, has a mass of 1,361 kilograms (kg) (3,000 lb). The weight of the MDB and the geometry and material properties of the MDB’s aluminum honeycomb contact face were derived from an adjustment of the average properties of the vehicle fleet (passenger cars and LTVs) in existence at the time of the development of the dynamic side impact regulation.

The test procedures focus on the dummy’s chest and pelvis acceleration responses, which have been correlated with crash and test data regarding the conditions that produce serious occupant injuries. The instrumented dummies must not exhibit chest accelerations and pelvic accelerations above specified thresholds in order to pass the test. The maximum rib and spine accelerations measured on the chest are averaged into a single metric called the Thoracic Trauma Index (TTI(d)), which has an 85g limit for 4‑door vehicles and a 90g limit for 2‑door vehicles. The pelvic acceleration has a 130g limit. [16]

[10] In 1996, under 2% of the passenger cars sold in the U.S. had chest side air bags installed as compared to around 38% in 2002. Also, in 1998, only 0.04% of passenger cars sold in the U.S. had head side air bag systems as compared to 22% in 2002.

[11] NHTSA and the research arm of the EU (the European Enhanced Vehicle Safety Committee) recognized the potential for harmonizing on the use of a side impact test dummy and focused efforts on the evolution of the Eurosid into the ES-2re.

[12]  "Side Impact Upgrade Research Update,"

[13] See Docket NHTSA-2003-14623.

[14] BMW Group, DaimlerChrysler Corporation, Ford Motor Company, General Motors, Honda, Hyundai, Isuzu, Kia, Mazda, Mitsubishi, Nissan, Subaru, Suzuki, Toyota and Volkswagen.

[15] Phase 3 consists of research using the IIHS barrier to assess the benefits of adding performance criteria for other body regions, specifically, the thoracic and abdominal regions. In addition, the research will also assess the potential benefits of performance criteria for a rear-seat test dummy and a 50th percentile male dummy (WorldSID). In Phase 4, the manufacturers and IIHS will investigate the opportunities to enhance structural interaction between vehicles in front-to-side crashes. The work will include an assessment of the IIHS side impact barrier with regard to the front-to-front compatibility performance criteria.

[16] At this time, the agency is conducting an evaluation of FMVSS No. 214 to determine the effectiveness of side padding in reducing injury risks in side impacts. The first part of the evaluation, focusing on older model year vehicles, was completed in 1999 (DOT HS 809 004, NHTSA Technical Report, October 1999). The principal finding of this Phase-1 evaluation was a statistically significant association of TTI(d) with side impact fatality risks in model year (MY) 1981-1993 passenger cars. The observed relationship was stronger in 2-door cars than in 4-door cars.