Relationship of Average Car Speed vs Speed limit

[Throckmorton]

Do you people really drive around at 80mph? That speed is uncomfortable for me because of my all terrain tires. Gas mileage also drops by probably 33% from 65 or 70.

 

[Throckmorton]

Originally posted by: thomsbrain
I did some research on this for a project once.

When Michigan raised their speed limits from 55 MPH to 65 MPH, average speeds increased by only 1 percent.

Here's a direct quote from a Department of Transportation study: "Raising speed limits by 5, 10, 15, or 20 mph? had a minor effect on vehicle speeds."

For the most part, people drive the speed at which they feel comfortable driving, regardless of the limit.

There is tons of data out there to support the theory that higher speed limits and higher overall speeds both support reductions in speed variance and accident rates. Support comes from reports from NHTSA, DOT, AAA, Institute of Transportation Engineers, etc.

The DOT are the first to admit that most highway agencies set speed limits below the average speed of the traffic and that speed limits are set artificially lower than their own recommended "85th percentile" speed.

Does the DOT have authority to lay the smack down and say "screw you Podunkville, make your speed limits reasonable and find another way to raise funds"?

 

[eflat]

Originally posted by: legoman666
I'll go 65 in a 55, 60 in a 50, and 72-75 in a 65. Rarely do I ever go over 75.

yeah I highly recommend not going 78mph.

 

[thomsbrain]

Originally posted by: Throckmorton

Originally posted by: thomsbrain
I did some research on this for a project once.

When Michigan raised their speed limits from 55 MPH to 65 MPH, average speeds increased by only 1 percent.

Here's a direct quote from a Department of Transportation study: "Raising speed limits by 5, 10, 15, or 20 mph? had a minor effect on vehicle speeds."

For the most part, people drive the speed at which they feel comfortable driving, regardless of the limit.

There is tons of data out there to support the theory that higher speed limits and higher overall speeds both support reductions in speed variance and accident rates. Support comes from reports from NHTSA, DOT, AAA, Institute of Transportation Engineers, etc.

The DOT are the first to admit that most highway agencies set speed limits below the average speed of the traffic and that speed limits are set artificially lower than their own recommended "85th percentile" speed.

Does the DOT have authority to lay the smack down and say "screw you Podunkville, make your speed limits reasonable and find another way to raise funds"?

I'm just guessing, but I get the impression they'd really like us all to go 40 MPH. The 85th percentile speed has more to do with reducing speed variance between cars (which is what causes most accidents, oddly enough ). The NHTSA would love everyone to go really slow, too, and they spin their statistics in that way, but the fact is that when the speed limit went up to 65 MPH, fatality rates per mile dropped. AAA found that as speed increases, speed variance decreases, so that isn't too surprising.

Consumer Research Magazine once reported that per mile driven, there are 300% more fatal crashes at 35 MPH than at 85 MPH. That is obviously due to the type of roads on which you'd drive those speeds, but it just goes to show that you're probably safer at 85 on the freeway than at 35 around town, and we happily drive around town all the time.