Expert: 75 mph might be safe

June 24, 2008
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A Purdue University civil engineering professor made news this week by rolling out a study showing the new 70 mph speed limit on rural interstates in Indiana caused virtually no increase in fatalities or injuries.

The study was prompted by the stateâ??s increasing the limit from 65 mph in summer 2005.

The engineer, Fred Mannering, thinks slower drivers went faster but fast drivers didnâ??t increase their speeds as much. The result was more people traveling at about the same rate, which reduces accidents.

Indiana could get away with bumping the limit to 75 mph if Illinois and Ohio ever move theirs from 65 to 70, Mannering says. If they donâ??t, the difference between 65 mph in Illinois and Ohio and 75 mph in Indiana would cause accidents.

â??As drivers go from one state to the next, there may not be this smooth transition,â?? he says.

What do you think? Will there come a point when Indiana should consider increasing the speed limit again?
  • The air resistence on a car increases dramatically at 70mph reducing gase mileage by up to 30%. From the view of conserving fuel, I don't think it would be a good idea.
  • Make it 100 mph !
  • The difference in gas mileage is not all that significant, I routinely drive up and down I-65 on a daily basis and see little difference in my gas mileage at 90 or 70 mph. Granted if you drive a large SUV with considerable drag (and torque geared large engine) you will see significant differences. The speed limit should be raised to at least 80.
  • I love to drive fast but have lowered my speed substantially since gas prices have spiked. By rarely going over 65 mph, I average over 30 mpg in my 2006 Jetta. When I was driving over 70, I would average 26 mpg or so.

    Raising the speed limit would be the height of foolishness.
  • Oh sure, raise it to 75 during an oil crisis. Your tax dollars hard at work at Purdue.
  • I'm for raising the limit, then ticketing people to do not Stay Right, Pass Left. We've been setting the cruise at 60-65 to gain some efficiency over driving at 70mph. I've been behind people travelling at 55--the best tradeoff speed for speed & efficiency.
  • Really just another example of narrow academic study. If you narrow the parameters enough, it could look like a good idea to go to 85 mph speed limits, but if Indiana is to join the rest of the country and the world in saving fuel, the wasted fuel that it takes to get to Chicago 15 minutes early is just not worth it. I think this engineer needs to wake up and talk to some other disciplines, like environmental scientists, global economists and so on. Purdue can do much better than this!
  • Increased fuel and patrolling costs, more violent collisions,and who cares, but more pollution. Why don't you Purdon'ts develop a better engine and quit boliermaking.

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