Light bulb analysis & investigation

Light Bulb Analysis

Headlight light bulb filament analysis

Car light bulb analysis is used to determine whether bulb was on or off during a collision and whether it's state was a causative factor.
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When vehicles are involved in a collision where there is impact to the headlight or brakelight assembly then the filaments of these bulbs experience the force of the collision resulting in distortion or breaking of the filament of the globe.

For incandescent light bulbs, a filament becomes more prone to deformation when the bulb is lit because the filament is extremely hot.

For candescent light bulbs, a filament is more rigid and when this undergoes collision forces the filament brakes indicating that it was not on at the time of the collision.

A light bulb filament can be deformed as a result of the collision and the amount of deformation is affected by proximity of the light bulb to the area of direct impact, the type of bulb, the amount of time the bulb was lit, etc.

A lack of deformation may not be definitive that a light bulb was not lit when the vehicle was struck, but a bulb that is extensively deformed is a clear indication that a bulb was lit during the collision.


To enquire please contact CIS on 0405 149 064 or email .

See also • Tyre examination,     • Vehicle examination

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Author: Pat McDonald