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Scott R. Falb Michael D. Pawlovich Iowa Department of Transportation

A Study of the Effects of Higher Speeds Limits on Iowa Expressways on Elderly Driver Crash Involvement. Scott R. Falb Michael D. Pawlovich Iowa Department of Transportation 29 th International Traffic Records Forum July 14, 2003. Preamble:.

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Scott R. Falb Michael D. Pawlovich Iowa Department of Transportation

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  1. A Study of the Effects of Higher Speeds Limits on Iowa Expressways on Elderly Driver Crash Involvement Scott R. Falb Michael D. Pawlovich Iowa Department of Transportation 29th International Traffic Records Forum July 14, 2003

  2. Preamble: • “This is not so much a presentation of what has been as it is about what will be.” Michael and Me

  3. Background on Speed Limit ChangesThe Nation • In 1995 national uniform maximum speed limit was abolished. • Many western and southern states increased their speed limits. • Many states east of the Mississippi and north of the Ohio rivers did not.

  4. Background on Speed Limit ChangesThe Midwest • South Dakota, Nebraska, Kansas, and Missouri raised their at least some of their speed limits above 65 mph. • Iowa, Minnesota* and Wisconsin did not. These states raised some expressway speed limits from 55 mph to 65 mph. • Those states that raised their speed limits beyond 65 mph experienced an increase in traffic fatalities. • Those states who did not raise their speed limits beyond 65 mph saw small decreases in traffic fatalities. * Minnesota raised interstate speed limits beyond 65 mph in 1997

  5. The Iowa Report on Speed Limit Increases • Iowa’s Safety Management System set up a committee of traffic safety professionals to study the effects of the 1987 speed limit increase to 65 mph, early data from states who automatically repealed the 65 mph maximum speed limit and produce a report in time for the legislative session. • The report showed that traffic deaths increased for a time after the 1987 then slowly resumed the previous downward trend. • The report showed that after the 1987 increase in the speed limit on Interstate highways there was a period where the majority of drivers drove at speeds that were below the new speed limit. • The study showed in time average driving speeds exceeded the new limit by the same amount as the old limits were exceeded.

  6. Iowa Speed Limit Debate • The Iowa Legislature debated raising the speed limit. • Iowa refused to raise speed limits on Interstate highways. • Iowa refused to raise speed limits on two lane highways and county roads. • Iowa did raise the speed limits on four-lane expressways from 55mph to 65 mph. • The speed limit change involved approximately 250 miles of expressway in the first year.

  7. Iowa Experience with the New Expressway Speed Limit • Iowa experiences a 497% increase in fatal crashes and a 587% increase in traffic fatalities on the original expressways where the speed limit was increased. • Other roadways in Iowa experienced a decline in fatalities. • Iowa’s overall fatalities declined while the surrounding states which raised their speed limits saw an increase in traffic fatalities. • Iowa expressway fatality rates have continued to outpace fatality rates on other roadways. • The number of miles with the 65 mph speed limit has increased from 250 miles to over 680 as more expressway miles were built.

  8. The Effects of Higher Speed Limits on Overall State Traffic Fatalities--Iowa/Kansas

  9. The Effects of Higher Speed Limits on Overall State Traffic Fatalities--Iowa/Kansas

  10. Iowa Experience with the New Expressway Speed Limit • Crash data analysts believe they are seeing an increase in the number of intersection fatal crashes involving drivers over the age of 60. • Crash data analysts believe they are seeing a higher number of crashes involving older drivers (over age 60) colliding with young driver (under age 30).

  11. The New Study • We have proposed to study crashes for five years before the speed limit increase and five years after to determine: • If older drivers are involved in more crashes and more fatal crashes since the speed limit change, • If older drivers are involved in more crashes and fatal crashes with young drivers, • What type of crashes are increasing (broadside, rear-end, head-on, etc.), • Is severity of these crashes increasing.

  12. Preliminary Data • Increase in broadside crashes • Increase in broadside left-turn crashes • Slight increase in rear-end crashes

  13. Questions? Scott R. Falb Phone: 515-237-3154 Email: scott.falb@dot.state.ia.us

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