The Traffic Accident Reconstruction Origin -ARnews-

Re: Speedometer Locked in Position Following a Collision

Wilt Nelson ([email protected])
Sun, 5 Apr 1998 14:11:43 -0400 (EDT)

The speedometer "needle" is not physically connected to the wheels on the roadway. An impact could occur when the driver had the wheels locked (zero speed) whicle sliding at 60 mph down the road or could be stopped on an icy surface spinning the wheels with the speedo indicating 100 mph when the impact occurred. "If" the speedo was stuck after the crash neither speedo would reflect the correct speed.
The theory of needle imprinting comes from the aircraft industry where the instrument panel in light aircraft is roughly 1 foot from the impact point. the front structure was not designed for crashes, and terminal speeds are 100 mph+. In some of these cases the different type of painted surfaces on aircraft instruments may imprint needle positions. In autmotive vehicles with 10 ft of crush space to the IP it is only the wish of some that this old tale were true. I have tested cars into concrete barriers at speeds up to 50 mph with out any imprinting.

Wilt
Wilt Nelson
[email protected]

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