Abstract
This report describes the circumstances surrounding wrong-way driving on California freeways and expressways. It provides some insight into the biographical background of the wrong-way driver. Data concerning observed wrong-way driving incidents during three separate 9-month periods were furnished by traffic enforcement officers. In addition 168 wrong-way drivers were interviewed. The effectiveness of various preventive devices installed on California freeways and expressways was tested. The before and after study method was used, using both incidents of wrong-way driving and wrong-way driving accidents. Reported incidents were also used to measure the efficacy of various off-ramp types in preventing wrong-way entry.