An Analysis of the Impact of Increased Speed Limits on Interstates and on Highways in Louisiana

National Highway Traffic Safety Administration2001PDFStatistical ReportSchneider, HelmutLouisiana Highway Safety CommissionUnited States. Department of Transportation. National Highway Traffic Safety Administration. National Center for Statistics and AnalysisUnited States. Department of Transportation. National Highway Traffic Safety AdministrationUnited StatesAdolescentsAdultsBefore and after studiesFatalitiesInjury severityInterstate highwaysRural areasSpeed limitsRural transportationRural highwaysTeenage driversUrban transportationStatistical analysisHS-809 367DTNH22-99-H-07004A law was passed in mid-year 1997, raising the speed limit on rural interstate highways in Illinois to 70 mph. Therefore, 1996 and 1998 were compared. Dependent variables were fatality count and injury severity. Factors controlled for were road type, speed limit, vehicle type, time of day, weather, driver age and gender and vehicle miles traveled by roadway type and month. Fatal crashes increased by 37% on interstates while fatal crashes in Louisiana as a whole increased by less than 1% during the same period. Fatal crashes on rural interstates increased by 2 crashes per month after the speed limits were raised in August, 1997. The number of injury crashes on interstates did not increase significantly but the number of property damage only did. The number of fatal crashes on urban interstates with speed limits below 70 mph increased by 13% but the number of fatal crashes on rural interstates increased by 46% during the same period. Involvement of young drivers (age 18 to 20) in fatal crashes on interstates more than tripled between 1996 and 1998. Youth driver (age 18-20) involvement in fatal crashes on interstates increased by 211% from 1996 to 1998, while the involvement of drivers aged 21 and older in fatal crashes increased by 70% during the same period.131