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2. Safety on the Highway
3. and , “Wrong-Way Driving: Off-Ramp Studies,” Institute of Transportation and Traffic Engineering, Department of Engineering, University of California, Los Angeles, California, 1965.
4. “The Interstate Sign Tests,” AASHO and U.S. Bureau of Public Roads, Washington, D.C., 1957, p. 22.
5. and , “Vehicle Spray Pattern Study,” Investigation 338, Minnesota Highway Department, Traffic Research and Design, Minneapolis, Minnesota, 1966.