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The results of the comparison of actual dynamic frontal crush behaviour from initial contact to maximum dynamic crush of 8 cars in 45% frontal overlap and 30 degree rigid barrier impacts at 50 and 56 kph respectively with the predicted responses from an overall frontal crush model are presented. The model used is based on the assumptions of the overall front structure deforming in a geometric manner and of the energy absorption properties in the full width barrier impact being the same as the energy absorption characteristics in other frontal crush configurations for identical average crush depths. The model uses a fundamentally different method of calculating average crush depth to that used in CRASH.

This paper examines the dynamic displacement-crushing force and dynamic displacement-absorbed energy behaviour of eight cars in full width barrier, 45% overlap rigid barrier and 30° angled barrier tests at 56, 50 and 56 kph respectively. This study shows the frontal crush behaviour of these cars can be divided into three regions or zones of constant force, these zones being associated with crushing of the front structure as far as the engine, the engine and rear front structure and the occupant compartment. The highest average crushing force is associated with crushing of the engine and rear front structure with lower average crushing forces required for the extreme front of the car and for the occupant compartment. It is hypothesised that the energy absorbed-dynamic displacement behaviour in the full width barrier test represents the energy absorbed-mean displacement for all other crush configurations.

When reconstructing vehicle accidents it is necessary in the course of the analysis to account for the uncertainty in the values of the key parameters such as tyre to road adhesion, the direction of vehicle movement both pre- and post-impact etc. In this paper Monte Carlo simulation methods are applied to accident reconstruction and accident avoidance analysis. Also the benefits which can be obtained from redundancy of the relationships describing the particular accident are examined. The results which can be obtained are demonstrated by a number of case studies.

This paper provides a theoretical explanation for the reported car size effect in frontal collisions. The frontal crush behaviour of the car population is examined arid shows that the specific energy absorption per unit mass propel-ties of the car population are independent of car size. Examination of single car crashes and car to car collisions in this context shows that the mean deceleration experienced by a car is inversely proportional to car length, is related to the square root of the collision closing speed arid to the inverse of the fourth I-oot of mass ratio and of crush depth. It is hypottiesised based on the Gadd severity index, for any specific car population and given degree of occupant protection within this population that Relative Injury Risk is proportional to the 2.3 power of mean deceleration.

This paper examines the deformation patterns of car fronts involved in both narrow object and offset frontal collisions and shows that the car side or sides not involved in direct crushing are pulled towards the centre of the car about a hinge point located 0.32 of the overall length to the rear of the front of the car. This corresponds with the location of the front of the car door/front bulkhead. The resulting crush profiles can be represented by simple geometric shapes. These are combined with a previously derived Specific Energy Absorption representation for the overall car population and applied to narrow object and pole impacts with car fronts. When compared with 19 staged pole impacts carried out by NHTSA high correlation is obtained and it is shown that the 95% confidence limits for calculated speed is +/- 9 km/hr.

Theoretical consideration of the energy absorption properties of structures shows that the specific energy absorption (E/Mk) is related to the normalised crush depth (d/L) and to a stress/density parameter. Examination of the crush characteristics of the car population shows that the mean stress/density parameter of the car population in frontal crush is independent of car size. On this basis regression is carried out which relates (2×E/Mk)½ to normalised crush depth (d/L)⅔ Using data from nine staged frontal car to car collisions this generalised specific energy absorption representation is compared with CRASH 3 and with Prasad's (5) individual car reformulation. It is shown that the accuracy of Delta V prediction with Prasad's individual car reformulation is superior to both the normalised crush depth model proposed here and to CRASH 3, both of which have similar accuracies.

A single segment pedestrian model is used to derive the throw distance - impact speed equations for the vehicle to pedestrian impact. Comparison with staged tests for adult pedestrians and cars shows that the model yields similar head contact positions and head impact velocities as those obtained experimentally. It is shown that the standard distance/velocity equation can be used to describe the pedestrian throw distance to vehicle impact speed relationship when an ‘Impact Factor’ term is introduced to specify the proportion of impact speed effectively transferred to the pedestrian by the impact process. The calculated throw distance and ‘Impact Factor’ to impact speed relations for 9 different car types are compared with the results of 84 staged dummy and cadaver tests. Statistically very highly significant correlation between the calculated and experimental ‘Impact Factors’ is obtained.