Citation

Brignola CJ. Collision 2010; 5(2).

Copyright

(Copyright © 2010, Collision Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Accident reconstructionists often need to determine whether or not a vehicle's lights were illuminated at the time of a crash. However, since a light bulb filament that is not brand-new may look significantly different than that from a new bulb, comparing new and in-service filaments can lead to erroneous results. This study compares the pre-crash light bulb filament shape with post-crash filament distortion of headlight and taillight bulbs involved in impacts with known collision parameters. This information should reduce the potential for false indication of filament deformation. A literature review was conducted to determine what past research has shown regarding how impact causes light bulb filament deformation. Then, several crash tests were performed. Before each crash test, every light in the vehicle was photographed in order to document the shape and condition of the light bulb filament. The age of the bulbs was unknown (as is usually the case in real-world accidents), but none were brand-new. In most tests, the vehicles were crashed with the headlight switch in the fully on position. In one test, two vehicles of the same model were tested--one with headlights on and the other with headlights off. The findings from this study confirm earlier research results. Significant collisions with direct impact to the headlight housing can cause brittle failure of de-energized light bulb filaments. Direct impact to the light housing is required to produce distortion than can be differentiated from manufacturing flaws, age sag or pre-existing filament shape. Magnitude of velocity change was not a good indicator of whether distortion will occur. The information collected in these tests can be used to help investigators of actual accident reconstruction cases determine details of the collision.