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The results of a traffic crash reconstruction often include vehicle speeds to address causation and changes in velocity to indicate crash severity. Since these results are related, they should be modeled in a probabilistic context as a joint distribution. Current techniques in the traffic crash reconstruction literature assume the the input parameters and results of an analysis are independent, which may or may not be appropriate. Therefore, a discussion of uncertainty propagation techniques with correlation and Monte Carlo simulation of correlated variables is presented in this paper. The idea that measuring a parameter with a common instrument induces correlation is explored by examining the process of determining vehicle weights. Also, an example of determining the energy from crush is presented since the A and B stiffness coefficients are correlated. Results show the difference between accounting for correlation and assuming independence may be significant.

The purpose of this study of snow plane sound levels is to provide quantitative information on snow plane sound emissions. The sound emissions of snow planes in the national park setting have been controversial and this research may provide decision makers and designers with some objective data for regulating sound levels. A snow plane is an over snow vehicle consisting of a passenger cabin supported on skis and driven by a light aircraft engine and propeller. In this regard, it is similar to the air-boats used on swamps and marshes. The pass-by sound levels of a variety of snow planes were measured at normal operating speeds. The pass-by testing included eight different snow planes. Two of these were equipped with dual muffler systems with balance tubes, four planes were equipped with dual muffler systems, and two of the snow planes had no muffling of the exhaust.