Car to car interaction in frontal collisions: A model for the behaviour of the car population and options for improved crashworthiness

Abstract

Accident database information shows that 40% to 50% of car occupants experience injuries that arc serious (AIS3+) and in many cases fatal. A significant proportion of the fatalities can be attributed to car-to-car frontal impacts (60%) while 57% of car-to-car collisions result in the occupants sustaining serious or greater (AIS3+) injuries. Those car occupant injuries and fatalities have led to concerted effort over the last four decades to understanding the mechanisms of occupant injury, and improving safety through improvement in crashworthiness and occupant safety systems. Analysis of real life car-to-car collisions has shown that car size and mass are important factors. This has led to significant research into car-to-car compatibility in frontal and other collisions. This paper review the fundamental mechanics of car-to-car collisions, sets out a model for the interaction between cars of different sizes in frontal impact, and validates the predicted mean Relative Injury Risk (RIR) versus Mass Ratio (Mr). the mass of the larger car over the mass of the smaller car, against real life data for serious injury (AIS3+). and for fatality. The paper then derives the predicted interrelationship between Relative Injury Risk (RIR), mass ratio (Mr), and Er, the ratio of collision energy absorbed by the larger car to that of the smaller car, and uses this interrelationship to examine the options available to improve the relative safety of the smaller car.