Chest deflection measurement is critical for the assessment of thoracic injury since the two most widely accepted criteria for chest injury (chest deflection and the viscous response) are based on deflection. One major issue with the measurement of chest deflection in crash test dummies has been the inability to accurately track motion of the chest at very high deflection speeds (above 10 m/s under certain circumstances). This limitation has increased the difficulty in evaluating some deployable safety devices, most notably airbags. When there is no interaction with the dummy, airbags deploy at velocities of 50 to 150 m/s. When there is interaction with the dummy, such as occurs in out-of-position tests with the chest in contact with the airbag module, airbags can deform the chest at deflection rates of 10 to 18 m/s.

Our main research goal was to develop a new sensor to measure chest deflection at all speeds of interest in the automotive environment (quasi-static to 18 m/s). The device developed, called the I/R-TRACC system (InfraRed - Telescoping Rod for Assessment of Chest Compression), uses two infrared LEDs inside of a telescoping rod. One LED is used as the emitter and the other is used as the receiver of the infrared light. The output of this device is a linear function of chest compression. The data presented in this paper shows that the IR-TRACC system appears to have met the design requirements set forth at the beginning of the project and should be suitable for any crash test dummy designed to measure chest deflection, including frontal and side impact dummies.