Maria Krafft

The Effectiveness of Electronic Stability Control (ESC) in Reducing Real Life Crashes and Injuries

Electronic Stability Control (ESC) was introduced on the mass market in 1998. Since then, several studies showing the positive effects of ESC have been presented. Objective. In this study, data from crashes occurring in Sweden during 1998 to 2004 were used to evaluate the effectiveness of ESC on real life crashes. The effectiveness was analyzed for different road conditions, and some accident types and injury levels. Methods. The study used statistical analysis. To control for exposure, induced exposure methods were used, where ESC-sensitive to ESC-insensitive crashes and road conditions were matched in relation to cars equipped with and without ESC. Cars of similar or, in some cases, identical make and model were used to isolate the role of ESC. Results. The study shows a positive and consistent effect of ESC overall and in circumstances where the road has low friction. The overall effectiveness on all injury crash types, except rear end crashes, was 16.7 ± 9.3%, while for serious and fatal crashes; the effectiveness was 21.6 ± 12.8%. The corresponding estimates for crashes with injured car occupants were 23.0 ± 9.2% and 26.9 ± 13.9%. For serious and fatal loss-of-control type crashes on wet roads the effectiveness was 56.2 ± 23.5% and for roads covered with ice or snow the effectiveness was 49.2 ± 30.2%. It was estimated that for Sweden, with a total of 500 vehicle related deaths annually, that 80–100 fatalities could be saved annually if all cars had ESC. Conclusions. ESC was found to reduce crashes with personal injuries, especially serious and fatal injuries. The effectiveness ranged from at least 13% for car occupants in all types of crashes with serious or fatal outcome to a minimum of 35% effectiveness for single/oncoming/overtaking serious and fatal crashes on wet or icy road surface. No difference in deformation pattern was found for cars with or without ESC.

How crash severity in rear impacts influences short- and long-term consequences to the neck

The main public-health problem concerning WAD are injuries leading to long-term consequences. Yet epidemiological studies mostly concentrate on data based on the injury outcome occurring shortly after the crash. The purpose of this article is to study the influence of crash severity in rear impacts leading to short and long-term consequences to the neck (WAD 1-3), lasting less than or more than 1 year. The influence of change of velocity as well as the car acceleration were investigated by using data from crash pulse recorders (CPR) installed in vehicles, involved in rear impacts. The influence of the car acceleration were also investigated by studying the frequency of occurrence of a tow-bar (hinge) on the struck car. Apart from real-life data, full-scale car-to-car crashes were performed to evaluate the influence of a tow-bar on the struck car. The crash tests showed that a tow-bar may significantly affect the acceleration of the car as well as that of the occupant. According to real-life crashes, a tow-bar on the struck car increased the risk of long-term consequences by 22% but did not affect the risk of short-term consequences. Out of the 28 crash recorder-equipped struck cars involving 38 occupants, 15 sustained no injury where the peak acceleration was 6g or less, 20 sustained short-term consequences where the peak acceleration was 10g or less. Three occupants from two different crashes sustained long-term consequences. The two crashes which resulted in long-term disabling neck injuries had the highest peak acceleration (15 and 13 x g), but not the highest change of velocity.

The Effectiveness of ESP (Electronic Stability Program) in Reducing Real Life Accidents

ESP (Electronic Stability Program) has recently been introduced onto the market in an effort to reduce the number and severity of loss-of-control automobile accidents. This reduction is expected to be particularly evident for accidents on roads with low friction (e.g., wet or icy conditions). This study aimed to evaluate the statistical effectiveness of ESP using data from accidents that occurred in Sweden during 2000 to 2002. To control for exposure, induced exposure methods were used, where ESP-sensitive to ESP-insensitive accidents and road conditions were matched in relation to cars equipped with and without ESP. Cars of similar, or in some cases identical, make and model were used to isolate the role of ESP. As predicted, the study showed a positive effect of ESP in circumstances where road surfaces have low friction. The overall effectiveness was 22.1 (±21) percent, while for accidents on wet roads, the effectiveness increased to 31.5 (±23.4) percent. On roads covered with ice and snow, the corresponding effectiveness was 38.2 (±26.1) percent. In addition, ESP was found to be effective for three different types of cars: small front-wheel drive; large front-wheel drive; and large rear-wheel drive.

Influence of Crash Pulse Characteristics on Whiplash Associated Disorders in Rear Impacts--Crash Recording in Real Life Crashes

There are variations in rear impacts causing Whiplash Associated Disorders (WADs) which lead to short- and long-term consequences. Most rear impacts lead to no injury or to symptoms that are temporary. Impacts where the duration of symptoms differs need to be separated in analyses in order to isolate representative rear impact conditions in which more long-lasting WADs occur. The correlation between injury risk and impact severity parameters based on acceleration levels is largely unknown. Since 1995, approximately 40,000 vehicles on the Swedish market have been equipped with crash pulse recorders measuring the acceleration time history in rear impacts. In the present study, the results from crash recording of 66 real-life rear impacts were analyzed, where the change of velocity and the crash pulse were measured. The injury status of 94 front-seat occupants was classified as: no injury, symptoms for less than one month, symptoms for more than one month, or symptoms for more than six months after the impact. The injury risk was calculated for different duration of symptoms and grades of WAD, 0-3, correlated to the crash severity parameters. For most of the occupants that sustained symptoms for more than one month, mean acceleration was more than 4.5 g, and change of velocity higher than 15 km/h. The average mean acceleration and change of velocity for this group were 5.3 g and 20 km/h, respectively. For those occupants that sustained symptoms for less than one month, the average change of velocity was 10 km/h and the mean acceleration 3.9 g. Mean acceleration was found to be the best candidate to predict duration of symptoms compared to change of velocity and peak acceleration. There was no significant correlation between different grades of WAD and crash severity. When designing test methods for evaluating vehicle safety concerning WAD, the acceleration pulse differs considerably, depending on whether the focus is on short-term or long-term consequences.

NECK INJURIES IN FRONTAL IMPACTS: INFLUENCE OF CRASH PULSE CHARACTERISTICS ON INJURY RISK

AIS1 neck injuries are the most frequent disabling injuries among car occupants in road traffic accidents. Although neck injury is mostly regarded as resulting from rear end collisions, almost one third of all neck injuries occur in frontal impacts. The injury mechanisms in both rear-end and frontal impacts are still not known, although different hypotheses exist. Since 1992, approx. 100,000 vehicles on the Swedish market have been equipped with crash recorders to measuring frontal impacts. This paper analyses the influence of different characteristics derived from the acceleration time history on the risk of short- and long-term disability to the neck in frontal impacts. The study includes injury outcomes from 187 restrained front seat occupants in 143 frontal collisions with an overlap exceeding 25%, where the crash pulses have been recorded using crash pulse recorders. The results show that the shape of the crash pulse influences the risk of long-term disability to the neck. The vehicle accelerations in the mid and last third of the crash pulse seem to be important. It is also shown how change of velocity and mean and peak accelerations influence the neck-injury risk. It is suggested that the risk of sustaining an AIS1 neck injury in frontal impacts could be reduced by using more effective pretensioners and more advanced belt-load limiters. These results may also have implications for neck injury mechanisms in rear-end impacts.

The Risk of Whiplash Injury in the Rear Seat Compared to the Front Seat in Rear Impacts

One hundred ninety-five rear impacts with both front- and rear-seat occupants in the struck car, where at least one occupant sustained permanent disability, were selected for study. There was a significantly higher disability risk for the female rear-seat occupant compared with the male driver. Furthermore, a higher risk was found for female rear-seat occupants compared with female front-seat passengers. The disability risk for occupants of the drivers seat was three times higher for females than for males, and four times higher for females in the rear seat. In the future, test methods should consider the risk of whiplash injury in both the front and the rear seat.

The use of seat belts in cars with smart seat belt reminders--results of an observational study

Recently, smart seat belt reminders (SBR) have been introduced in cars. By increasingly reminding drivers and passengers if they are not using the seat belt, the intention is to increase the belt use to almost 100%. Objective. The objective was to study if there were differences in drivers seat belt use between cars with and without SBR. Methods. Drivers of cars with and without SBR were observed concerning seat belt use. The case (cars with SBR) and the control group (cars without SBR) were similar in all major aspects except SBR. In all, more than 3,000 drivers were observed in five cities in Sweden. Results. In cars without SBR, 82.3 percent of the drivers used the seat belt, while in cars with SBR, the seat belt use was 98.9 percent. The difference was significant. In cars with mild reminders, the use was 93.0 percent. Conclusion. It is concluded, that if the results can be generalised to the whole car population this would have a dramatic impact on the number of fatally and seriously injured car occupants.

Intelligent Seat Belt Reminders—Do They Change Driver Seat Belt Use in Europe?

Objective. Many modern cars have seat belt reminders (SBRs) using loud and clear sound and light signals. These systems have developed over the last few years. This study investigates how these modern systems influence the seat belt use in real-life traffic in built-up areas in some European cities. Methods. The data were collected by field observations in major cities in six European countries and in five cities around Sweden. A selection of car models having seat belt reminders (SBR) were compared to a fleet of similar car models without such reminders. Results. A significant difference in seat belt wearing rate was found in the cars with seat belt reminders. For all observations, the total seat belt wearing rate was 97.5% +/− 0.5% in cars with SBR, while it was 85.8% +/− 0.8% in cars without. There were differences in seat belt use in the different observation locations. The lowest seat belt use was found in Brussels/Belgium with a use rate of 92.6 +/− 2.2% in cars with seat belt reminders and 69.6 +/− 3.1% in cars not fitted with reminders. The highest seat belt use was found in Paris/France where 99.8 +/− 0.4% of the drivers used the seat belt in cars with reminders and 96.9 +/−1.1% were belted in cars without reminders. Conclusion. Seat belt reminders fulfilling Euro NCAPs seat belt reminder protocol are increasing the seat belt use in daily traffic significantly. Around 80% (82.2% +/− 8.6%) of the drivers not putting the belt on without a seat belt reminder do so in cars equipped with an SBR that has a light signal and an associated loud and clear sound signal.

Injury severity assessment for car occupants in frontal impacts, using disability scaling

Injury classification and assessment is one of the most important fields of injury prevention. At present, injury assessment focuses primarily on the risk of fatalities, in spite of the fact that most people who are injured survive the trauma. The net result of a fatality-based approach is that safety and vehicle engineers must make decisions with an incomplete, and sometimes misleading, picture of the traffic safety problem. By applying disability scaling reflecting long-term consequences to injury data, the most significant disabling injuries can be identified. The priorities change with the level of disability used in the scaling. In this study, the risk of permanent medical disability due to different injuries was derived and linked to abbreviated injury scale (AIS) values for 24,087 different injured body regions. This material is based on insurance data. To study how the importance of different bodily injuries changes with different severity assessments in a realistic real-world injury distribution, Swedish insurance industry disability scaling was applied to 3066 cases of belted Volvo drivers involved in frontal collisions. Crash severity was included in the study by using equivalent barrier speed (EBS). When lower levels of disability are included, injuries to the neck and the extremities become the most important, while brain and skull injuries become the most prominent at higher levels of disability. The results presented in this article should be regarded as a contribution to the development of a suitable disability scaling method. The results can also be utilized to further injury research and vehicle design aimed at reducing injuries which have the most important long-term disability consequences.

The Properties of Safety Performance Indicators in Target Setting, Projections and Safety Design of the Road Transport System

Road traffic Safety Performance Indicators (SPIs) are becoming increasingly used as an instrument for the planning and monitoring of safety progress. SPIs form an intermediate step between actions and final outcome in terms of casualties in road crashes. It is understood that SPIs are closely related to outcome; and that it is also possible to use them in calculations and predictions of both actions and final outcome. In the present study, it was found that some of the properties assigned to SPIs could be questioned. An assumption of linearity between SPIs and final outcome was partly rejected. It was also found that 100% fulfillment of a set of SPIs could lead to very low mortality, demonstrating the importance of handling SPIs simultaneously.