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In August of 1994 the Major Accident Investigation Team (M.A.I.T.) became aware of a collision involving a well maintained five year old minivan with 79,000 miles. The collision resulted in the death of a 1½ year old child. The cause of the collision was loss of brake pressure due to vaporization of the brake fluid. Over the years other investigators within the state have occasionally suspected brake fluid failure as a possible link to the cause of certain collisions. However, there was no accident record data on motor vehicle collisions resulting from brake fluid failure, and no standardized procedure for inspecting a vehicle and identifying the cause of the collision as a brake fluid failure. The Washington State Uniform Collision Report has a classification for “defective brakes”. The category is not specific as to the type of defect in the braking system.

The appropriate friction coefficient value for real world collision scene investigation is essential to the accident reconstructionist. Many of these values are obtained from resistance tables published periodically from the 1930's. Tire-roadway friction values are dependent on the type of instrument used to obtain the value, the type of braking force available, the type of roadway contamination and numerous other physical factors. Friction value data tables are available in numerous texts, but these values occasionally need to be improved upon. The purpose of this paper is to present the findings of a five year study of friction values for slippery surfaces at “real world” collision scenes located in the western part of the state of Washington.

Motorcycle collisions by their very nature are difficult at best to analyze and/or reconstruct. Motorcycles come in as many different types, models and styles as do passenger vehicles and trucks. The inherent problems of load changes and articulation are enough to discourage anyone from reconstructing these type of collisions. This document is a result of efforts by members of the Washington State Patrol Traffic Investigation Division and members of the Washington State Patrol Academy. The purpose of the tests was to use the G-Analyst to determine the most appropriate value for both rear and front brake resistance during brake application and to make some comparisons of acceleration rates and deceleration rates.