Often times there is evidence to indicate whether a vehicle's lights were on or off at the time of the collision. “Hot shock” typically indicates that a bulb was on at the time of a collision. It is evidenced by deformation to the filament due to the forces in a collision. "Cold shock" typically indicates that a bulb was off at the time of the collision. This is evidenced by a brittle fracture to the filament as a result of the forces from the collision. Sometimes more complicated issues arise when evaluating a vehicle's lighting system. This includes damaged light bulbs, improper wiring, aged light bulbs, and more. A filament analysis is commonly used when determining whether a vehicle’s headlights, turn signals, taillights, and/or brake lights were on at the time of a collision.