The 85th percentile speed is where collision involvement is minimal. It comes directly from analysis of data. Since it made sense that the safest speed to drive should be legal, setting the speed limit to this value was born. Studies of setting the speed limit in this manner show a decrease in collisions and little change in actual driver speeds.
Wrong Way MFFY! 3382John, They are referring to MUTCD, Manual on Uniform Traffic Control Devices. You can read it here. Specifically, they are talking about their Holy Grail, setting speed limits to the...
I believe you've already been pointed to the reference material.
Shifter techniqueThis page: says that to move the shifter when changing gear you should (in this example, changing from 2nd to 3rd): "move the knob up to neutral...
Cirillo, J.A., Interstate System Accident Research Study II Interim Report II. Public Roads, Vol 35, No 3, August 1968 plus 1, pp. 71-75. Federal Highway Administration. Synthesis of Speed Zoning Practice. Report No. FHwA-RD-85-096. Washington, D.C. July 1985. Federal Highway Administration. Traffic Speed Trends. Washington, D.C. 1968 plus 1-1975. Solomon, D., Accidents on Main Rural Highways Related to Speed, Driver, and Vehicle. Bureau of Public Roads (precursor to FHwA). July 1964. Federal Highway Administration. Effects of Raising and Lowering Speed Limits. Report No. FHwA-RD-92-084. McLean, VA. June 1996. Tignor, Samuel C. and Warren, Davey. Driver Speed Behavior on U.S. Streets and Highways. Insbreastute of Transportation Engineers, 1990 Compendium of Technical Papers. Orlando, FL August, 1990. David L. Harkey, et. al., "buttessment of Current Speed Zoning Criteria," Transportation Research Record, no. 1281, 1990.
