Study: Higher Interstate Speed Limits are Safe

[MindPilot]

Source: thenewspaper.com

Purdue University this week released results of a study showing that there was no change in the number of accidents after Indiana increased the maximum freeway speed limit to 70 MPH on July 1, 2005. Civil engineering Professor Fred Mannering led the team that looked at accident data from one year before this change -- when the top legal speed was 65 MPH in rural areas -- for comparison with accident rates a year later.

(snip)

Mannering's study noted that expert opinion is divided on this controversial subject. For example, a 1999 report sponsored by the Insurance Institute for Highway Safety claimed increased limits resulted in higher accident rates. The insurance industry depends on speeding tickets to provide surcharge revenue. Other independent studies, including a 1994 review of the effect of the change from the national 55 limit to 65 on rural roads, have arrived at a contrary conclusion that the higher limit, in fact, saved lives.

Mannering used a statistical model to calculate accident probabilities based on his own examination of data from 390,000 accidents recorded by the Indiana Vehicle Crash Record System. After applying the model, he concluded that the increased speed limit had no effect on the probability of suffering an accident nor did it increase the severity of accidents that did occur.

In 2006, only 5.78 percent of the state's accidents were caused by unsafe speed, a decrease from 2004. The study also noted that a 15 MPH increase in the speed limit did not produce a 15 MPH increase in the actual speed traveled. Instead, real speeds increased only 12 MPH. The report suggested that speed limit changes may have had a negative impact on some non-interstate rural roads and that future changes for secondary roads should be evaluated on a "case-by-case basis."

Read more: http://www.thenewspaper.com/news/24/2442.asp

[sinkingfeeling]

1. Raising speed limits will certainly help conserve gasoline, right? (sarcasm)

[MindPilot]

6. The study dealt with accidents not fuel savings.

This is statisical evidence which shows that higher speed limits do not increase the accident rate on interstate highways.

So for those double nickel advocates who say "it saves lives too", this pretty much dispels that myth.

[snooper2]

33. My 1999 S-10 with 4.3L vortec V6 gets best mpg at around 55

Also have a 2006 Grand Prix V6 that gets best mpg around 70...

My motorcycle 650 V-star gets it's best mpg cruising around at 40, while my friends Triumph Rocket 2300 gets best mpg around 75


It's all due to gearing so you can stop with the sarcasm :rofl:

[izquierdista]

2. De jure or De facto?

Raising the number on a sign from 65 to 70 probably has zilch impact on the actual speed of traffic. This bozo needs to get his ass out of his basement computer lab, calculating probabilities out to the nth place and sit on the side of a highway with a radar gun and collect some actual, real data. In addition, a competent statistician would control for other variables such as: weather differences in the time periods under study, rates of driving while intoxicated, rates of cell phone use while driving, and differences in road construction activity in the time periods under study, and as many other confounding variables as possible, given the small differentials in the observed variables under study.

What a bonehead. :crazy:

[MindPilot]

7. I'm not sure I understand your point.

The whole idea is to factor out higher speed limits as a cause of accidents.

In other words if the speed limit is increased and the accident rate stays the same or decreases, then the lower speed limit was not preventing accidents. Something else is the problem.

[izquierdista]

8. He did an incomplete study

Suppose drunk driving was much different one year than the other, due to say law enforcement activity. Accident rates could be much different with that as the major factor. He needs to do a multi-variate analysis and control for other variables, which he hasn't done. The observation that small changes in speed limit don't really correlate too well with changes in accident rates tells me nothing. It is a non-result.

[MindPilot]

11. Can we see the result of the studies you've done on the subject?

Obviously your flawless methodology yielded indisputable results which traffic engineers the world over must be using.

[izquierdista]

12. Wouldn't do you any good

All you have shown here is that you have no grasp of statistics. :dunce:

[MindPilot]

14. And all you've shown is a lack of common sense.

Which is odd for someone claiming to be much smarter than a university professor who does this sort of research for a living.

So maybe you should just bow out of this thread until you have something substantive to offer.

[thunder35]

3. sounds good let people drive faster

and keep the government out of the speed business

[Javaman]

4. That's very energy conscious of you...

:eyes:

last time I checked driving is still a privilege not a right.

[MindPilot]

5. Yep. the question I always ask the "slow is safe" crowd:

"If you do not trust me to operate my vehicle in a reasonable and prudent manner, why the FUCK do you give me a license?"

[Baclava]

9. I can't drive 55.....but I don't drive like an idiot around town.

It's usually the morons that speed around in traffic, screeching brakes and diving into lanes to get one car ahead who are usually the same ones driving slow in the fast lanes on the interstates.

I hate them all.

[timtom]

10. I'm a speeder.

And I also pay the f**k attention to what I'm doing when I'm driving (as I'll bet you do as well). To me, driving is a total commitment that demands 99% of my attention at all times.

[skoalyman]

13. same here if someones talking to me on the passengers side

I don't turn my head back and forth talking to them my eyes are always on the road each side and behind me. lot of wrecks are caused from not paying attention.

[snooper2]

34. Most accidents happen way below highway speeds...

:hi:

[Jack_DeLeon]

15. I support increasing the speed limit...

I think low speed limits are stupid. That being said I'm not driving much past 60mph these days due to the cost of fuel.

[Orsino]

16. So driving more slowly is smart...

...but mandating slower driving is stupid?

[Jack_DeLeon]

20. Yes I generally dont think its a good idea...

for us to use government to take away choice from people or force it upon them.

[Orsino]

26. So, companies' lowering their CO2 output is a good thing...

...but it would be stupid to have laws requiring them to do so?

[Zachstar]

17. Then you will support lowering the speed limit.

Or you dont give a rats a** about our energy situation.

[Jack_DeLeon]

21. "because if your not with us then you are against us."

:eyes:

[Zachstar]

23. In this matter yes because the poor are who will suffer the hardest.

They don't drive around in Corvettes or Minis they drive around with barely running early 90 civics and other cheapo cars. They are keeping it slow just to keep from having to empty the wallet at the gas station for just one more day.

So yes you want to turn this into a Bush/Star Wars thing go ahead but we have to reduce it NOW we dont have 2 decades to talk about it. I would rather be sworn at by people driving Vipers than see gas prices rise yet again because demand has not slowed down enough.

Bring the HW speeds DOWN!

[JVS]

24. There's no rule that they have to drive 70. If people want to go 55 that's their business.

[Zachstar]

27. Where do you live cause where I live it is against the law to go a large speed under the speed limit

[Jack_DeLeon]

28. I live in Texas...

have you read your actual laws? Is it illegal, or are police just ticketing people for it in the hopes that they wont even contest it. Cause with rising fuel prices chances are they arent getting as many speeding tickets so they might just be trying to generate revenue in other ways.

If it is illegal in your state then perhaps you should work to change your law instead of trying to change the laws of all the states. Its pretty presumptuous to think that all the states should all be the same in regards to laws.

[Bill McBlueState]

29. minimum interstate speed is usually 40

Thus, the poster's suggestion of driving 55 in a 70 shouldn't get anyone into trouble.

[lumberjack_jeff]

32. Where I live, it's against the law to hold up traffic.

Going slow, provided you're not holding up lots of other drivers, is not a problem.

[Chuggo]

18. I drive fast.

That's why I'm crazy.

[JVS]

25. YES! CHUGGO IS ON DU

And you better not be somone's sockpuppet

[Doctor_J]

19. If I am driving in a 65 mph zone, the person driving 75 is much less dangerous

than the one driving 55. I personally go about 73 or so because I have better things to do with $100 than pay for Bitch Daniels' inaugural ball.

[JerseygirlCT]

30. I do think greater problems, safety-wise, are caused by

inattentive drivers and slow drivers not keeping to the right.

When traffic is all moving well, people are able to leave good space between cars.

More and more lately, I've gotten stuck behind a slow mover in the left lane. Who then suddenly gets up to speed, then slows down. Inevitably, the person is on the phone - obviously paying no attention to the road. THOSE are the people I wish they'd stop.

That said, traffic here is definitely moving much faster than say 5 years ago. If you're in the left lane, you'd best be doing 80 or better in order to keep with the traffic - that's high even for me. And that's a problem, too - when the difference between the average speed of the different lanes is so big, that's bound to cause difficult situations.

But the phones... geez, people!

[KillCapitalism]

22. It is, but only under PERFECT conditions.

It mostly depends on driver ability, but I've done 120 on desert highways in the middle of nowhere for miles (don't flame I know it's stupid, but I was young then). The problem is that if you hit a large pothole, an animal runs out into the road, or you hit some road debris, then you're gonna be toast at those speeds.

[lumberjack_jeff]

31. Speed doesn't kill, delta-v does.

On the typical 55mph interstate, 55mph traffic shares the road with 75mph traffic. Also, some of the more cagey speeders move to the parallel state highway where there are fewer cops. On the typical 70mph highway, scofflaws drive 80, but those scofflaws avoid the two-lane roads.

Set the speed limit at a level that 95% of cars could negotiate the road in question safely. If you set it significantly lower than this, safety suffers and the impact on fuel consumption is minimal.