Tungsten filament vehicle lamps are examined in an effort to determine if a lamp was ON or OFF at the time of a crash. The ON or OFF condition of the lamp can assist in accident reconstruction and determination of fault.

Determination of ON or OFF is generally based on how the impact from the crash affects the configuration or condition of the filament inside the lamp. ON filaments may show stretching or discoloration of the filaments. OFF filaments may show cold breakage or natural burnout of the filament.

Filament examinations cannot be performed on LED lighting or HID lamps.

Filament examinations include continuity testing and microscopy.

Broken filament

Updated August 11, 2020