Crash Testing

Dr. Mohamed Aty, PE

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Introduction

Road traffic crashes annually kill more than one million people worldwide, injuring another thirty-eight million (5 million of them seriously). The death toll on the world’s roadways makes driving the number one cause of death and injury for young people ages 15 to 54. With the introduction of airbags and crash testing, the number of people killed and injured by motor vehicles has decreased in many countries. Today, more than ever before, safety sells cars. For car buyers it is a key element of their purchasing decision ^{(1), (2)}.

CRASH TESTING OF VEHICLES is a way to determine if best practice in terms of occupant protection has been implemented for a new car. It is a way to get an early indication of the safety level of new cars ⁽³⁾. Crash testing is used for different purposes: It is used to evaluate new safety systems in the vehicle (e.g., Airbags, Head Restraints, and safety restraint belts) ⁽⁴⁾, evaluate different kinds of vehicles, evaluate if roadside safety appurtenances are safe enough to be used on roads and streets such as Safety Barriers, Crash Cushions ⁽⁵⁾, and Bridge Rails (e.g., New Jersey Safety-Shape rail) ⁽⁶⁾. Crash testing is also used to study serious crash injuries (e.g., Neck (Whiplash) injuries, Lower limb injuries, and head injuries) ^{(7), (8)}, and invalidation of crash and drive recorders ^{(9), (10)}. Crash tests were used also to evaluate the design of the highway lighting supports ⁽¹¹⁾, and to evaluate the work zone traffic control devices ⁽¹²⁾.

Crash Tests for Car safety Rating and Evaluation

In 1978 The National Highway Traffic Safety Administration (NHTSA) began the crashworthiness assessment of new cars by running high-speed frontal barrier crash tests ^{(13), (14)}. The New Car Assessment program (NCAP) was to develop a methodology for providing consumers with a measure of the relative safety potential of automobiles.  In the NCAP test the cars are crash-tested at a nominal velocity of 35 mph (56 km/h) into a rigid barrier. The International New Car Assessment program (NCAP) ratings provide a useful basis for comparing vehicle safety. The following sections describe the tests used in rating.

The Euro NCAP is designed also to provide a fair, meaningful and objective assessment of the impact performance of cars. It is intended to inform consumers, so providing an incentive to manufactures as well as giving credit to those who excel at occupant or pedestrian protection. The tests used are based on those developed for legislation by the European Enhanced Vehicle safety Committee (EEVC), for frontal and side impact protection of car occupants and for the protection of pedestrians hit by the front of the cars ⁽¹⁵⁾.

Full –width frontal impact crash test

This procedure is used by the National Highway Traffic Safety Administration (NHTSA-USA) and the National Organization for Automotive Safety & Victim’s Aid (OSA-Japan). Dummies are seated in the driver's and front passenger seats.  The vehicle crashes head-on into a rigid concrete barrier at 35 mph (56 km/h).  Afterwards, researchers measure and evaluate the impact on the dummies' head, chest, and legs.  The resulting information indicates a belted person's chances of incurring a serious injury in the event of a crash. This test provides very high deceleration forces to the test dummies and is particularly well suited to the evaluation of occupant restraint systems such as seat belts and air bags ^{(1), (16)}.

Frontal offset crash test

This procedure is used by the Euro-NCAP (Europe), the Insurance Institute for highway safety (IIHS- USA) and the National Organization for Automotive Safety & Victim’s Aid (OSA-Japan). In the test, a vehicle is aligned with a rigid barrier with a deformable aluminum face so that 40% of the width of the vehicle strikes the barrier on the driver's side (10% offset from the centerline - hence offset test).  Dummies are seated in the driver's and front passenger seat (driver's seat only in the IIHS tests), and the vehicle runs into the barrier at 40 mph (64 km/h), in order to measure and evaluate the impact on the dummies' head, chest, and legs - as well as to check the condition of the deformed vehicle. This test represents the forces involved in a typical head-on collision of two vehicles weighing the same that are traveling at 40 mph (64 km/h). Because a smaller portion of the vehicle's structure sustains the force, the impact on the dummy is weaker than in a full frontal impact.  However, there is greater vehicle body deformation, making it suitable for the evaluation of potential injury caused by intrusion to a vehicle's occupants. Structural performance is based on measurements indicating the amount and pattern of intrusion into the occupant compartment during the offset test. This assessment indicates how well the front-end crush zone managed the crash energy and how well the safety cage limited intrusion into the driver space. Performance of the structure/safety cage is a major component of each vehicle's overall evaluation ^{(1), (17)}. The tables in Appendix (A) show the ratings of about 300 cars tested using the frontal offset crash test. ⁽¹⁸⁾. Also Figure (1) shows both the Full Width Frontal test and The frontal Offset test ⁽¹⁾.

Figure (1): Full Width and Frontal Offset Crash Tests.

Source: Introduction to Auto Safety ad Crash-Testing ⁽¹⁾.

Side impact crash test

In this test, a stationary vehicle with dummies in the driver's and front passenger seat is rammed by a 2090 lb (950 kg) moving trolley with a crushable aluminum face, going 30 mph (50 km/h), directly centered on the driver's seating position.  

The NHTSA test differs from the others in a number of ways.  NHTSA runs a 3,015 lb (1370 kg) moving trolley into the left side of a car twice, once at the left front driver's position and once at the left rear passenger's position. While other side-impact tests are conducted at an impact angle of 90 degrees (perpendicular), the NHTSA test is conducted with the trolley's wheels turned 27 degrees to the right, so that the force of the impact comes from a point 63 degrees from the centerline of the test vehicle (although the trolley is facing perpendicular [90 degrees] to the centerline). As with frontal impact testing, the side impact test is conducted at five mph above the federal standard, which means the deformable barrier hits the car at 38 mph (61km/h). The Side impact test procedure is shown in Figure (2).

Figure (2): Side Impact Crash Tests.

Source: Introduction to Auto Safety ad Crash-Testing ⁽¹⁾.

Pole or Head Protection Tests

In Europe, approximately a quarter of all serious-to-fatal injuries happen in side impact collisions. Many of these injuries occur when one car runs into the side of another. But in Germany over half such injuries occur when a car hits a pole or a tree.

To encourage manufacturers to fit head protection devices, a pole or head protection tests have been added to the Euro-NCAP protocols. Side impact airbags help to make this kind of crash survivable. They are also very effective in other types of side impact accidents such as being hit by another vehicle where the bonnet enters the window at head height ⁽²⁾.

Pedestrian Protection

 Euro-NCAP began a testing program geared towards protecting pedestrians as well as vehicle occupants.  Pedestrians are much more vulnerable than car occupants when a crash occurs.  Euro-NCAP's pedestrian evaluation tests the most hazardous areas of each model. This is done by firing dummy parts at those areas, simulating 25mph (40km/h) accidents involving adults and children. A simulated leg is impacted against the bumper, an upper leg against the front edge of the bonnet, and dummy heads, both child- and adult-sized, at points on the bonnet. Each of the heads are tested at six different locations and each limb at three, making 18 impacts in all. Measuring devices inside the dummy parts record the severity of impact, and the results are used to rate each car. Figure (3) shows the test dummies and locations on the car.

Figure (3): Pedestrian Crash Tests.

Source: Introduction to Auto Safety ad Crash-Testing ⁽¹⁾.

No cars yet tested have provided sufficient protection to meet all of the requirements of the proposed legislation established by the European Enhanced Vehicle safety Committee (EEVC).  However Euro-NCAP provides an incentive for manufacturers to do more to protect pedestrians.  Currently a median is taken allowing each car's performance to be described as better or worse than average. No legislation setting out minimum requirements for pedestrian safety currently exists, but the proposed requirements could eventually become law.  Because the requirements are only in the proposal stage and Euro-NCAP is the only agency participating in these tests.

As mentioned in the previous sections, the New Car Assessment Program (NCAP) was implemented in different countries. The following sections describe the Crash tests procedures for NACP in these countries:

a -The United States

1- NHTSA NCAP

In 1978 the New Car Assessment Program (NCAP) in the United States was initiated by the National Highway Traffic Safety Administration (NHTSA) with the primary purpose of providing consumers with a measure of the relative safety potential of vehicles in frontal crashes. NCAP now supplies consumers with important comprehensive information, including frontal- and side- crash test results, to aid them in their vehicle purchase decisions. The ultimate goal of NCAP is to improve occupant safety by providing market incentives for vehicle manufacturers to voluntarily design their vehicles to better protect occupants in a crash and be less susceptible to rollover, rather than by regulatory directives ^{(1), (16)}.

NHTSA chooses new vehicles which are predicted to have high sales volume, vehicles which have been redesigned with structural changes, or have improved safety equipment for testing. These vehicles are purchased from dealerships, just as a consumer would, and not supplied by the manufacturer.

NHTSA classifies vehicles by weight. Passenger cars are categorized as mini (1,500-1,999 lbs. curb weight), light (2,000-2,499 lbs. curb weight), compact (2,500-2,999 lbs. curb weight), medium(3,000-3,499 lbs. curb weight) and heavy(3,500lbs.and over curb weight.) The other categories are sport utility vehicles (SUVs), light trucks and vans.

2- IIHS-NCAP

The Insurance Institute for Highway Safety (IIHS) has been working on finding out what works and doesn't work to prevent motor vehicle crashes in the first place and reduce injuries in the crashes that still occur. Its work includes fully instrumented crash tests, plus in-depth study of serious, on-the-road crashes. Scrutinizing the outcomes of both controlled tests and real collisions gives researchers -- and ultimately the public -- a better idea of how and why occupants get injured in crashes. This research, in turn, leads to vehicle designs that reduce injuries. Among the most important studies in (IIHS) is an ongoing series of frontal offset crash tests at 40 mph (64 km/h). Such tests provide the basis of the Institute's crashworthiness evaluations, which assess and compare how well passenger vehicles protect their occupants in crashes ⁽¹⁷⁾.

b -Europe

 Euro-NCAP

In Europe, more than 170,000 people die in motor vehicle accidents each year, and a further 5 million are injured.  Clearly, improved vehicle safety is essential to improve road transport safety.  Moreover, safety has become a powerful factor in new car sales ⁽¹⁾.

Euro-NCAP is a resource for consumers regarding vehicle crash safety. The program also promotes safety developments, and credits car manufacturers focusing on safety. Euro-NCAP is a crash test program, which was set up in 1996. The program has tested more than 64 different car models and the results were published. The cars are tested in a frontal collision and in a side collision. The possibility of adding a pole (head protection) test has been introduced in the year 2000. A pedestrian protection test is also included.

Euro-NCAP use stars to indicate the safety level of a vehicle. A combined star rating shows the protection level in the front collision and side collision together. The star scoring is based on point scores for the front and side. Maximum 34 points can be achieved by adding 16 front and 18 side points. The star borders are at 8, 16, 24, and 32 points. Until spring 2000 a maximum of four stars has been possible. Now a fifth star can be achieved if the point score is 32 points or more. No car has achieved that result till May (2000). Lie et al ⁽³⁾ found that there was a strong and consistent overall correlation between Euro-NCAP scoring and risk of serious and fatal injury and high ranked vehicles produce approximately 30% less fatal and serious injuries compared to low-ranked vehicles.

c -Australia

ANCAP

The Australian New Car Assessment Program (ANCAP) commenced in 1992. It was based on the 35 mph (56 km/h) full-width frontal barrier test developed by the NHTSA for the US-NCAP.  Since then, its development has been heavily influenced by Euro-NCAP and the IIHS. It was clear from the observation of real-world crashes that an offset test was required.  Between 1993 and 1999 ANCAP conducted both full-frontal and offset crash tests, basing ratings on both tests. Starting in 2000, ANCAP aligned its test and assessment procedures with those of Euro-NCAP ⁽¹⁾. 

The Australian New Car Assessment Program (ANCAP) gives consumers consistent information on the occupant protection level of vehicles in serious front and side crashes. The program is supported by Australian and New Zealand automobile clubs, the State government road and transport authorities in Queensland, NSW, Westerm Australia & South Australia, the New Zealand Government and the Australian Federal Government ⁽¹⁹⁾.

d -Japan

Japan NCAP

In Japan, Casualties (fatalities + Injuries) due to traffic accidents increase on a yearly basis and reached about 950’000 in 1996 and 1.16 million in 2000. The Ministry of Land, infrastructure and Transport, through cooperation with the National Organization for Automotive Safety & Victims' Aid, has performed testing and evaluated the safety of automobiles currently on the market. The results of these tests are publicly released under the title New Car Assessment Japan ⁽²⁰⁾.

The National Organization for Automotive Safety & Victims' Aid (OSA) sponsors Japanese NCAP tests (full-frontal, frontal offset, and side impact) on the most popular Japanese home-market vehicles ⁽¹⁾. OSA which is under the guidance of the Ministry of Transport, evaluates the safety performance of automobiles currently available in Japan.  The test vehicles are chosen from the country's best-selling cars, starting in model year 1996. The objective of New Car Assessment Japan is to increase the use of safe automobiles by providing an environment in which users can easily select such vehicles. This also promotes the development of safer vehicles by automobile manufacturers. This assessment publishes the results of tests on 24 vehicle models. This covers approximately 51% of the automobiles available in the Japanese market. This assessment provides an overall evaluation of collision safety through the results of three collision tests, including the new test for offset frontal collisions.

Crash Tests for Roadside Appurtenances safety

In order to revise safety regulations for automobiles, it is necessary to understand accident realities ⁽⁹⁾. Accidental exits from the roadway are one of the major factors of road accidents: 25% to 40% of all accidents, according to the type of road. The solution to this safety problem consists in removing dangerous obstacles when possible and in implementing road vehicle restraint systems between the carriageway and the obstacle, or of the change of level ⁽⁵⁾. The following discuss the tests implemented to achieve the Roadside Appurtenances Safety.

Road crash tests are used to evaluate if roadside safety appurtenances are safe enough to be used on roads and streets such as Safety Barriers and Crash Cushions, Table (1) summarizes the test designation for the various roadside safety features specified in the National Cooperative Highway Research Program (NCHRP) Report 350 guidelines under Test Level 3 (TL-3), including the test vehicle, the nominal impact speed and angle, and the impact point on the device. Also, an assessment on whether the test is affected by impact speed only (A) or by a combination of impact speed and angle (B) is provided in this table ⁽²¹⁾.

Test level 3 (TL-3) is the basic test level used for devices on the National Highway System (NHS). Table (1) shows that the nominal impact speed for all tests under Tl-3 conditions in NCHRP Report 350 is 62.2 mph (100 km/hr), except for the low-speed tests for support structures, work zone traffic control devices, and breakaway utility poles (tests 60, 70 and 80). Two tests have a nominal impact angle of 25 degrees, which are test 11 for the length-of-need and test 21 for the transition section of a longitudinal barrier. For terminals and redirective crash cushions, a lower nominal impact angle of 20 degrees is used for redirectional (including reverse direction) impacts, two test vehicles were used: the 4409 lb (2000 kg) 3/4-ton pickup truck (2000P) and the 1808 lb (820-kg) passenger car (820C) ⁽²¹⁾.

A—Impact speed only, B – Combination of impact speed and angle

2000p—2000kg (4,409 lb) pickup truck, 820C—820kg (1,808 lb) passenger car, LON—Length of need

Table (1): Test Conditions inn the NCHRP Report 350.

Source: Assessment of NCHRP Report 350 Test Conditions ⁽²¹⁾.

Crash Tests for Studying Serious Crash Injuries

Neck Injuries

During a rear-end car collision the struck vehicle is subjected to a forceful forward acceleration and the car occupant is pushed forward by the seat back. The head lags behind due to its inertia, forcing the neck into a swift extension motion. The head moves forward relative to the torso and may stop with a somewhat flexed neck posture. This head and neck motion is called ‘whiplash motion’ ⁽²²⁾.

As a result of more than ten years of concentrated research efforts in the area of neck injuries in car collisions, Volvo’s Whiplash Protection Study (WHIPS) presents a holistic method for dealing with the whiplash problem; combining experience with known biomechanical research and development of engineering tools. Three guidelines were identified: (a) reduce occupant acceleration; and this guideline can be verified by measuring the dummy acceleration in sled tests: (b) minimize relative movement between the head and torso; and this guideline can be verified by the dummy response in a crash test, and (c) minimize the forward rebound to the seat belt; and this guideline can be satisfied by ensuring high energy absorption of the backrest during a crash. It is suggested that if these guidelines are adhered to the seat design, the risk of neck injury in rear-end impacts can be reduced.

The WHIPS study include development of a new seat, which has shown to have considerable potential in offering increased protection against neck injuries in rear-end impacts. The development of the dummy called BioRID used in crash tests offers the Whiplash protection study an excellent tool for better evaluation of new systems for improved neck injury protection in rear-end impacts ⁽⁸⁾.

1- Head Restraints

In a rear-end crash, if an occupant’s head is unsupported it lags behind the torso (The torso is the body excluding the head, neck and limbs). This causes the neck to change shape and causes neck injury. The first step for prevention is the head restraint that is behind and close to the back of an occupant’s head during the crash.

The differential movement of the head and torso in a rear-end crash can be limited be either a high seat back or a separate head restraint positioned behind and close to an occupant’s head. In recognition of this, front-seat head restraints have been required in all new cars sold in the United States since the beginning of 1969, but even today the head restraints in many new cars either are not, or cannot be positioned behind and close to many occupants’ heads and therefore, do not meet the necessary minimum requirements for effective whiplash injury prevention.

In the 1960’s, rear impact sled tests with human volunteers were conducted, researchers reported no injuries even at relatively high speeds when subjects were on a seat with a rigid back and their heads were touching a head restraint with a small amount of padding ^{(4), (23)}.

Beginning in 1969, the National Highway Safety Bureau extended this requirement to all new cars manufactured for sale in the United States. Federal Motor Vehicle Safety Standard (FMVSS) 202 established performance requirements for head restraints, which have remained unchanged since 1969. The principal geometric requirement of this standard specifies that restraints in their highest positions (measured parallel to the plane of the torso) must extend at least 27.5 in. above the seating reference point.

Today’s head restraints measure up to the two basic criteria of adequate height and minimal distance behind occupants’ heads. The Insurance Institute for Highway Safety has evaluated head restraint geometry in a large number of recent model passenger vehicles. Measurements of the vertical and horizontal proximity of the restraints to the head of an average-size male were obtained using a specially designed head form mounted on a standard H-point mannequin.

The first survey covered 1995 models and, of the 164 vehicles measured, only 5 (3%) were rated as having restraints with good geometry; 117 (71%) were rated poor. The second survey in 1997 models found essentially the same results. Only 7 vehicles (3%) out of 247 models measured had head restraints with good geometry, and 156 vehicles (62%) were rated poor.

2- Dynamic testing and advanced head restraints

In Sweden, research was conducted to assess the differences in stiffness and elasticity of seat backs by using dynamic testing. A consortium of Chalmers University, Autoliv (a restraint system manufacturer in Sweden), Saab, and Volvo has developed a dummy neck and spine with 24 elements designed to mimic the motion of a human head, neck, and spine in rear impacts. This dummy defined as BioRID (biofidelic rear impact dummy) was designed to measure the rate of relative motion of the head and torso; this in turn allows the neck injury criterion (NIC) to be calculated. The new neck injury (NIC) predicts the risk of injury as a function of the head-neck motion ⁽²²⁾. Human volunteer tests indicate that a NIC of 13 or less does not produce neck injuries with long-term symptoms ⁽⁴⁾.

The insurance Institute for Highway Safety ran two sets of relatively low-speed rear-end impact test of cars using BioRID to assess some newer head restraint designs. In these tests, a 4000-pound movable barrier with a rigid front end hit the rear ends of cars with BioRID dummies in the front seats at 15 mph. The first series consisted of three impacts of 1999 Volvo S80 models. In each test there were two different front seats, one with which was the original equipment S80 seat with a new design system (the whiplash injury prevention system WHIPS). The other front seat in each test was from a Volvo S70 with a fixed back and head restraint with good geometry.

In the first two tests, an undamaged S80 was hit by the moving barrier. In one test the WHIPS seat was on the driver side, and in the other it was on the passenger side. In the third test, an S80 (one WHIPS seat, one S70 seat) with rear-end damage from the first test was hit again. The results of the three tests are summarized in Table (2)

Table (2): Neck injury criterion (m²/s²) results from 15 mph rear crash tests, 1999 Volvo S80 models.

Source: Head Restraints-the neglected countermeasure ⁽⁴⁾.

Table (2) shows that the WHIPS seats produced lower NIC values than the S70 seats, and the NICs were lower than 15, the proposed injury assessment reference value.

The second series of tests involved two car models: a 1997 Pontiac Grand Prix with a head restraint and seat back designed to meet new criteria established by General Motors for head restraint geometry and seat back stiffness, and a 1995 Saab 9-5 model with an energy absorbing seat back ^{(5), (20)}. The Grand Prix restraint was tested only in the up position, while the Saab 9-5 restraint was tested in both the up and down position. Table (3) shows the results.

Table (3): Neck injury criterion (m²/s²) results from 15 mph rear crash tests.

Source: Head Restraints-the neglected countermeasure ⁽⁴⁾.

Table (3) shows that in the up position, the NIC of the Saab was very low (12); in the down position, it was comparable with the results for the S70 shown in Table (1).

The availability of crash test dummies with necks and spines that react like a human’s in a rear-end crash, together with the development of neck injury criteria, mean future head restraint designs can be based on dynamic testing ⁽²⁾.

A new crash dummy and a neck injury criterion will be very important components in a future rear-impact crash test procedure ⁽²²⁾.

3- Seat Characteristics in low-speed rear impacts

In Japan, it was found that the largest percentage of fatalities occurred in frontal impacts in 1996 (49.1%), followed by side impacts (11.3% left side and 9.9% right side), with very few fatalities occurring in rear impacts (2.5%). In contrast, the largest number of injuries occurred in rear impacts (43.5% of injuries were rear impacts).

An investigation of the nature of the injuries suffered in rear impacts revealed that approximately 90% were neck injuries ^{(24), (25)}.

It was found that neck injuries are a characteristic of low-speed rear impacts ⁽²³⁾. It is very important to know how seat characteristics affect occupant motions in low-speed rear impacts. The position of the head restraint and the stiffness distribution of the seat-back are selected as parameters expressing seat characteristics and were testing using crash dynamic tests ⁽²⁴⁾.

To analyze the effect of the seat characteristics on dummy motions and human volunteer motions, sled tests simulating low-speed rear impacts were conducted with some seats which has different characteristics.

A sled test was conducted simulating low-speed rear impacts in Tsukuba University with a volunteer. The sled impact velocity was set at 8 km/h. and using different seats with different stiffness. A high-speed camera and X-ray cineradiography were used to capture the visible and cervical vertebral motions.

It was found that the position of the head restraint influenced the visible motions of the car occupant. The seat system that moves the head restraint forward and upward at the time of impact causes the neck injury in rear impact crashes. Also it was concluded that the neck injury decreased when the stiffness of the occupant seat was reduced ⁽²⁴⁾.

Lower limb injuries

Nowadays, with airbags installed in vehicles, the incidence of head and torso injuries were reduced. But lower limb injuries are taking high significance. As the number of crashes involving air bag-equipped cars has increased, the number of crash victims whose most severe injury was a lower limb injury has also increased ⁽⁷⁾.

Statistics suggests that foot and ankle injuries account for 8-12% of all moderate-to-serious injuries sustained by motor vehicle occupants involved in frontal crashes  ^{(7), (27), (28), (29)}. Several frontal crash tests were conducted to test the loads on the dummies examined. Crandall et al ⁽⁷⁾ described six crash tests conducted by NHTSA to emphasize lower limb injuries: The tests included frontal car-to-car offset, offset oblique and full frontal barrier crashes using a mid-size vehicle and a compact car. Pre-crash and post-crash digitized profiles of the footwell region were used to calculate the levels of footwell intrusion. A Hyprid III dummy was placed in the driver’s position of each vehicle tested. It was found from that test that right legs (placed on the accelerator pedal) tended to have greater loads than left legs indicating that pedal interaction may significantly contribute to lower limb injuries.

Using Crash Tests to validate high performance drive-recorders for measuring crash and near misses

Under existing crash investigation methods used worldwide, data items such as driving velocity, impact velocity and crash configuration are estimated from vehicle body deformations, tire slip marks and witness accounts. These crash analysis has limitations in examining the details of accident situations and causes; new techniques are used. Two types of drive-recorders were developed for recording data on automobile crashes and near misses; these two recorders are accident drive recorder (ADR) and near miss and accident drive-recorder (NADR).

Different types of validation tests were conducted. Non-crash driving tests were carried out on ADR or NADR-equipped vehicles to evaluate the accuracy of their data on acceleration, angular velocity, driving velocity, accident avoidance maneuvers and near miss recording thresholds. Then vehicle crash tests were performed in various configurations, such as rear-end and lateral collisions, in order to evaluate the accuracy of the data recorded by ADR or NADR on acceleration, vehicle trajectory and velocity changes as well as video images. In all of the validation tests, the ADR and NADR were evaluated by comparing their data with the data obtained by conventional measuring devices as reference.

A rear-end collision test was conducted where a lead and intermediate vehicles were stopped one meter apart, and the striking vehicle was made to crash into the rear end of the intermediate vehicle. The striking and the intermediate vehicles were equipped with an ADR and an NADR respectively, but the lead vehicle did not have any drive recorder.

The recorders showed that the striking vehicle struck the rear end of the intermediate vehicle three times. In response, the intermediate vehicle struck the lead vehicle in front three times. This was a series of collisions between the three vehicles due to the action and reaction of the three vehicles detected by the ADR, NADR, and the reference-measuring device alike. The ADR and NADR was considered to provide a reliable analysis of acceleration.

It was found that both drive-recorders are capable of obtaining accident data with greater accuracy and a wider scope than currently available data. Therefore, the data made available by ADR and NADR should assist in improving the existing injury criteria, crash test procedures and dummy development so that safety regulations can be revised more effectively ⁽⁹⁾.

Also crash tests were conducted to evaluate the accuracy and precision of a device called the Crash Pulse Recorder (CPR) ⁽¹⁰⁾. The CPR is a low-cost one-dimensional crash recorder designed for measuring the acceleration time history in field accident studies. The aim of the CPR was to measure the crash pulse as near the center of gravity in the car as possible. This pulse is an indication of the crash severity required in accident reconstruction and analysis. In most car models the CPR is mounted under the driver or passenger seat.

 The performance of the CPR in tests with different pulse shapes at different velocities and different crash angles was investigated. After several tests on a sled-testing track, a large series of full-scale tests was conducted to evaluate the systematic and random errors of the CPR in different types of collusions, and to determine how accurately the CPR measures the crash pulse shapes at different velocities, and also to estimate how rotation and different angles of the crash affect the measurements. A total of 21 cars containing 51 CPRs (Up to six CPRs were installed in the same car to determine the random error) were involved in 14 tests. Kullgren et al ⁽¹⁰⁾ presents the values of systematic and random errors of each parameter measured in each experiment for the different cars measured.

Test Strategies

Crash tests in the form of full-scale impact tests and sled tests are run in the laboratory in order to achieve the required input data to validate a simulation model or to test a safety device. A large quantity of data (behavior of vehicle and restraint system, dummy trajectories, forces and accelerations measured in the dummies) is used for this analysis.

If car manufacturers carry out crash tests at only one speed and with only one dummy size there is a risk of sub-optimizing the car safety systems. There might be a risk of sub-optimization of the occupant safety, if the evaluation of the test strategy (only one test speed and one dummy size) for occupant protection systems is too limited.

Standardized frontal crash test which have been used worldwide for many years to estimate the “safety level” of passenger cars are generally carried out at 30 or 35 mph, using 50^th percentile “male” dummies as occupants. The results at other crash speeds and using other dummy occupant sizes are not so often considered. If crash test carried out with one dummy size and at one speed are used to estimate the safety potential of a car or a safety design features, the results may not apply to the broad spectrum of occupant sizes and impact velocities ^{(13), (30)}. This can create a risk of investing great resources into incorrect measures. The consequences of this inadequate test strategy for new safety systems can be instead of achieving a reduction in injuries with the new system, the result might be an increase in the number of injuries out in the real traffic environment.

If high speed crash testing is given too much priority in the development of vehicles without considering the performance at lower speeds. There is a risk of sub-optimizing the total vehicle safety ^{(13), (30), (31), (32)}.

An important part of the analysis method is the correlation of occupant injuries and dummy responses from the simulations. Such a correlation is valid only under certain conditions ^{(13), (33)}. The correlation is generally applicable if the crash mode of the laboratory tests is equivalent to the real life accident type, a valid severity parameter is used, and that the protection criterion is a valid measure of injury production.

It is essential that any simulations that are undertaken and that are to collectively represent the overall accident profile, must be undertaken with sufficient detail. It is important to ensure the correct degree of detail; i.e., bearing in mind the uncertainties and variations inherent in both the accident data and the crash tests and simulations, it is very difficult to try to simulate the mechanisms at too detailed level. To reduce the risk of erroneous reconstruction, it is essential that important parameters from accident data can be reconstructed as faithfully as possible in the simulations.

The results from crash tests should represent at least those crash situations that are close to the simulation pre-conditions (crash configuration, crash test speed, and given dummy). Even if there are natural variations in crash data, which affect the reliability of the correlation to laboratory data, assessment reliability with regard to personal injury is improved compared with the situation in which no account is taken of impact and occupant parameters.

Parameters To be Considered during Analysis

·        Crash Severity is one of the most important parameters to consider during analysis and evaluation of the safety potential of different products. It represents any form of violence to which the occupant was subjected whether injured or not. The correlation of injury data and dummy responses implies, for example, that at a certain neck injury criterion NIC value in laboratory crashes is related to a certain neck injury risk in a corresponding crash situation in traffic ^{(13), (30)}. It is important to clarify the injury mechanisms, as far as possible for different types of injuries, and to find the dummy responses which correlate best with the injuries.

·        The size of the occupant is another essential parameter. Depending upon their size, occupants come into contact with different parts of the interior during a crash, and this will affect the risk of injury. It is important to know that the tolerance level varies from occupant to another.

In order to improve the future reliability of analyses of the safety potential of different products and systems, the improvement of the quality of essential background data and methods must continue. Some of the most essential areas area:

1-     The identification of important injury mechanisms.

2-     The development of measurement in the dummies which correlate to the different types of injuries.

3-     The development and validation of simulation models.

4-     The development of crash severity parameters which have a good connection to the risk of injury.

5-     Continued development of methods for the connection of accident data and laboratory/simulation data for different crash situations.

Conclusions and Recommendations

In the previous sections, different crash tests were discussed as an important safety tool. Different purposes and procedures of these tests were shown. The main conclusions and recommendations are as follows:

·        Because death on the world’s roadways makes driving the number one cause of death and injuries, so safety in the car it is a key element of car buyers purchasing decision ^{(1), (2)}.

·        In frontal offset crash test, the impact on the dummy is weaker than in a full frontal impact.  However there is greater vehicle body deformation, making it suitable for the evaluation of potential injury caused by intrusion to a vehicle's occupants.

·        In Europe, approximately a quarter of all serious-to-fatal injuries happen in side impact collisions. Many of these injuries occur when one car runs into the side of another. Side impact airbags help to make this kind of crash survivable.

·        Euro-NCAP began a testing program geared towards protecting pedestrians as well as vehicle occupants.  Pedestrians are much more vulnerable than car occupants when a crash occurs. Euro-NCAP provides an incentive for manufacturers to do more to protect pedestrians. No legislation setting out minimum requirements for pedestrian safety currently exists, but the proposed requirements could eventually become law. 

·        The ultimate goal of NCAP is to improve occupant safety by providing market incentives for vehicle manufacturers to voluntarily design their vehicles to better protect occupants in a crash and be less susceptible to rollover, rather than by regulatory directives ^{(1), (16)}.

·        Accidental exits from the carriageway are one of the major factors of road accidents: 25% to 40% of all accidents, according to the type of road. The solution to this safety problem consists in removing dangerous obstacles when possible and in implementing road vehicle restraint systems between the carriageway and the obstacle, or of the change of level ⁽⁵⁾.

·        The first step for preventing neck injury is the head restraint that is behind and close to the back of an occupant’s head during the crash. The principal geometric requirement of this step specifies that restraints in their highest positions (measured parallel to the plane of the torso) must extend at least 27.5 in. above the seating reference point.

·        The availability of crash test dummies with necks and spines that react like a human’s in a rear-end crash, together with the development of neck injury criteria, mean future head restraint designs can be based on dynamic testing ⁽⁴⁾.

·        The development of the dummy called BioRID used in crash tests offers the Whiplash protection study an excellent tool for better evaluation of new systems for improved neck injury protection in rear-end impacts ⁽⁸⁾. New crash dummies and a neck injury criterion will be very important components in a future rear-impact crash test procedure ⁽²²⁾.

·        It was found that the position of the head restraint influenced the visible motions of the car occupant. The seat system that moves the head restraint forward and upward at the time of impact causes the neck injury in rear impact crashes. Also it was concluded that the neck injury decreased when the stiffness of the occupant seat was reduced ⁽²⁴⁾.

·        It was found from that test that right legs (placed on the accelerator pedal) tended to have greater loads than left legs indicating that pedal interaction may significantly contribute to lower limb injuries.

·        If car manufacturers carry out crash tests at only one speed and with only one dummy size there is a risk of sub-optimizing the car safety systems. There might be a risk of sub-optimization of the occupant safety, if the evaluation of the test strategy (only one test speed and one dummy size) for occupant protection systems is too limited.

·        In order to improve the future reliability of analyses of the safety potential of different products and systems, the improvement of the quality of essential background data and methods must continue. Some of the most essential areas area:

1-     The identification of important injury mechanisms.

2-     The development of measurement in the dummies which correlate to the different types of injuries.

3-     The development and validation of simulation models.

4-     The development of crash severity parameters which have a good connection to the risk of injury.

5-     Continued development of methods for the connection of accident data and laboratory/simulation data for different crash situations.

References:

1-     Agencies and Explanations. Introduction to Auto Safety & Crash-Testing.  http://www.crashtest.com/intro/ie.htm.

2-     European New Car Assessment Program (Euro-NCAP) –Crash Tests

      http://www.euroncap.com/tests.htm

3-     Lie, A., and Tingvall, C. How Does Euro Ncap Results Correlate to real Life Injury Risks – A Paired Comparison Study of Car-to-car Crashes. Paper Presented at the IRCOBI conference, Montpellier 20 September 2000. http://www.euroncap.com/research/swedish_study.doc

4-     O’Neill, B., Head Restraints—The Neglected Countermeasure. Accident Analysis and prevention, Volume 32,  2000, Pages 143-150

5-     International Crash Test Standards for Roadside Safety Features – Transportation Research Board – National Research Council, Washington D.C., Transportation Research Circular (No 451- December 1995)

6-     Holloway, J., Faller, R., Pfeifer, B., Post, E., and Davidson, D., Performance Level 2 tests on the Missori 30-in. New Jersey Safety-Shape Bridge Rail. Paper presented at the Annual Meeting of the Transportation Research Board in January 1992 – No.1367 (Highway and Facility Design), Washington, D.C.

7-     Crandall, J., Martin, P., Sieveka, E., Pilkey, W.,  Dischinger, P., Burgess, A., O’Quinn, T., and Schmidhauser, C. Lower Limb response And Injury in Frontal Crashes. Accident Analysis and prevention, Volume 30, No. 5, 1998, Pages 667-677.

8-     Jakobsson, L., Lundell, B., Norin, H., and Isaksson-Hellman, I. WHIPS – Volvo’s Whiplash Protection Study. Accident Analysis and prevention, Volume 32, 2000, Pages 307-319.

9-     Nishimoto, T., Arai, Y., Nishida, H., and Yoshimoto, K. Development of High Performance Drive-Recorders for Measuring Accidents and Near Misses in the Real Automotive World. Society of Automotive Engineers of Japan, Volume 22, 2001, Pages 311-317.

10- Kullgren, A., Lie, A., and Tingvall, C. Crash Pulse Recorder – Validation in Full Scale Crash Tests. Accident Analysis and prevention, Volume 27, No. 5, 1995, Pages 717-727.

11- Pfeifer, B., Holloway, J., Faller, R., Post, E., and christensen, D., Full-Scale crash Tests on a Luminaire Support 4-Bolt Slipbase design. Paper presented at the Annual Meeting of the Transportation Research Board in January 1992 – No.1367 (Highway and Facility Design), Washington, D.C.

12- Polivka, K., Rohde, J., Faller, R., and Sicking, D., Crash Testing and Analysis of work Zone Sign Supports. Paper submitted to the 81^st Annual Meeting of the Transportation Research Board in January 2002.

13- Norin, H., Koch, M., Ryerberg, S., and Svensson, S. Combining Accident Data and Laboratory Simulation Data Reduces the Risk for Sub-Optimized syafety Systems in Cars. Safety science, Volume 19, 1995, Pages 57-69.

14- Hcakney, J.J., and Quarles, V., The New Car Assessment Program – status and Effect. National Highway Safety Administration (NHTSA0, 1982.

15- European New Car Assessment Programme (EuroNCAP) – Assessment Protocol and Biomechanical Limits. Version 3, April 2001      http://www.euroncap.com/protocols/EuroNCAP_Assessment_Protocol_V3.pdf.

16- U.S. National Highway Traffic safety Administration (NHTSA)- US Car Assessment Program (US-NCAP). (FAQ)      http://www.nhtsa.dot.gov/cars/testing/ncap/Info.html.

17- The Insurance Institute for Highway Safety (IIHS), Highway Loss Data Institute. http://www.hwysafety.org/vehicle_ratings/vrc.htm http://www.hwysafety.org/vehicle_ratings/ce/def.htm

18- Federation Internationale De L'automobile (FIA). Crash tests http://www.fia.com/homepage/selection-a.html

19- National Roads and Motorists' Association (NRMA)- ANCAP Crash Tests http://www.nrma.com.au/Page/Public?PageId=mot_ct_about_ancap

20- National Organization for Automotive Safety and Victim’s Aid (OSA)-Japan. New Car assessment Japan (Japan NCAP) http://www.osa.go.jp/anzen/html2001e/as101.htm

21- Mak, K., and Bligh, R., Assessment of NCHRP Report 350 Test Conditions. Paper presented at the 81^st Annual Meeting of the Transportation Research Board in January 2002.

22- Svensson, M., Bostrőm, O., Davidsson, J., Hansson, H-A., Håland, Y., Lővsund, P., Suneson, A., and Säljő, A. Neck Injuries in Car Collisions – A Review Covering a Possible Injury Mechanism and the Development of a New Rear-Impact Dummy. Accident Analysis and prevention, Volume 32, 2000, Pages 167-175

23- Wicklund, K., Larsson H., 1998. Saab Active Head Restraint (SAHR) – seat design to reduce the risk of neck injuries in rear impacts. SAE Technical Paper Series 980297. Society of Automotive Engineers, Warrendale, PA.

24- Watanabe, Y., Ichikawa, H., Ono, K., Kaneoka, K., and Inami, S. Influence of Seat Characteristics on Occupant Motion in Low-speed Rear Impacts. Accident Analysis and prevention, Volume 32, 2000, Pages 167-175.

25- Japan Traffic Safety, Traffic Greenpaper, November 1997, Pages 115-118.

26- Eichberger, A., Geigl, B.C., Moser, A., Fachbach, B., and Steffan, H. Comparison of Different Car Seats Regarding Head-Neck Kinematics of Volunteers During Rear End Impact. Proceedings of 1996 International IRCOBI conference on the Biomechanics of impact, Pages 115-118.

27- Otte, D., Rheinbaben, H., and Zwipp, H. Biomechanics of Injuries to the Foot and Ancle Joint of Car Drivers and Improvements for an Optimal Car Floor Development. Proceedings of the 36^th Strapp Car Crash Conference, 1992, Seattle, WA, SAE Paper No. 922514, Warrendale PA.

28- Crandall, J. R., Klopp, G.S., Klisch, S., Sieveka, E., Pilkey,. W. and Martin, P. Research Program to Investigate Lower Extremely Injuries. In-depth Accident Investigations – Trauma Team Findings in Late Model Vehicle Collisions, SAE Paper No.940711. Society of Automotive Engineers, Warrendale PA.

29- Krüger, H., Heuser, G., Kraemer, B., and Schmitz, A. Foot Loads and Footwell Intrusion in an Offset Frontal Crash. Proceedings of the 14^th ESV Conference, 1994, Germany, Paper 94-S4-0-03.

30- Norin, H., and Isaksson-Hellman, I., Injury Potential Prediction of a Safety Design Feature. A Theoretical Method based on Simulation and Traffic Accident Data. Presented at the IRCOBI Conference, September 9-11, Verona, Italy.

31- Horsch, J.D., Evaluation of Occupant responses Measured in Laboratory Tests. SAE Technical Report no. 870222. Society of Automotive Engineers (SAE), Warrendale, PA, USA.1982.

32- Norin, H., Jernström, C., Koch, M. et al., Avoiding Sub-Optimized Occupant Safety by Multiple Speed Impact Testing. 13^th International Technical Conference on Experimental Safety Vehicles, Paris, 1991. (Paper No. 91-S9-0-89).

33- Korner, J., A Method for Evaluating Occupant Protection by Correlating Accident Data With Laboratory Test Data. SAE Technical Report no. 870222. Society of Automotive Engineers (SAE), Warrendale, PA, USA.1989.

Appendix A

Crash Tests: 

Table of NCAP Offset Crash Tests

Source: Federation Internationale De L'automobile (FIA) ⁽¹⁸⁾.

4WD - The more stars the better.

Key:[Excellent/*****][Good/****][Acceptable/***] [Marginal/**][Poor/*]
+ indicates "struck through star" - risk of life threatening injury
# Indicates offset speed 60km/h. All other tests at 64km/h. Coloured year indicates current model.
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4WD - LARGE - The more stars the better.

Key:[Excellent/*****][Good/****][Acceptable/***] [Marginal/**][Poor/*]
+ indicates "struck through star" - risk of life threatening injury
# Indicates offset speed 60km/h. All other tests at 64km/h. Coloured year indicates current model.
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LARGE/MEDIUM CAR - The more stars the better.

Key:[Excellent/*****][Good/****][Acceptable/***] [Marginal/**][Poor/*]
+ indicates "struck through star" - risk of life threatening injury
# Indicates offset speed 60km/h. All other tests at 64km/h. Coloured year indicates current model.
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LUXURY - The more stars the better.

Key:[Excellent/*****][Good/****][Acceptable/***] [Marginal/**][Poor/*]
+ indicates "struck through star" - risk of life threatening injury
# Indicates offset speed 60km/h. All other tests at 64km/h. Coloured year indicates current model.
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PASSENGER VAN - The more stars the better.