Speed Limits

[John Boothby]

I was just sittin around think'n, and I was wondering just how they come up with the posted speed limits. I know the simple answer, but are there any highway engineers out there that can answer this?

[Franke]

Interesting thought about traffic engineering. We had a road next to the interstate that was 40 mph for years. Then one day the city put a traffic light at a T intersection of the road and removed the stop sign. The speed limit was dropped to 30 mph. ??? People began receiving tickets from the men in blue immediately thereafter because of the habit of driving at 40. Seems a lot of folks complained to city hall about the ridiculous new speed limit and lo and behold the speed limit went back to 40mph. Hmmmm. Could it be that speed traps are a consideration or politics or public safety or roadway design or....... where did common sense go anyway?

[John Boothby]

Originally Posted by Franke

Interesting thought about traffic engineering. We had a road next to the interstate that was 40 mph for years. Then one day the city put a traffic light at a T intersection of the road and removed the stop sign. The speed limit was dropped to 30 mph. ??? People began receiving tickets from the men in blue immediately thereafter because of the habit of driving at 40. Seems a lot of folks complained to city hall about the ridiculous new speed limit and lo and behold the speed limit went back to 40mph. Hmmmm. Could it be that speed traps are a consideration or politics or public safety or roadway design or....... where did common sense go anyway?

This is what got me thinking. Is it based on some formula using highway design; automobile design; driver ability and or political considerations?

[efnfast]

I heard somewhere, who knows where, that our interstate highways were designed for 80 mph.

[John Boothby]

Originally Posted by efnfast

I heard somewhere, who knows where, that our interstate highways were designed for 80 mph.

Ok, but back in the 50's when the highway system was designed the average auto was way less capable then today's autos. So, what speed would be just as "safe" for auto's of today? Back in the 50's cars did not even have seat belts! poor brakes, less traction, etc. Now Texas has increased some speed limits to 85 from what I hear. I know for a fact that parts of I-15 in Utah has been increased to 80mph. So, could this be a movement to increase speed limits to a level more up to date with modern auto technology? Just think'n, ya know.

[XfireZ51]

John,

Don't forget that in the 70's speed limits had more to do w gas mileage than
automobile capability. Prior to that speed limits were in the 70-75mph range depending.

[ZRXMAX]

Many factors to consider.
Condtion of road surface where many factors are present here in socal. We have some rough freeways. Occassionally a pothole on an interstate or state road will harm a large number of vehicles in a short period of time.

Traction and visibility also play a part. The rolling hills of many states as compared to the flat deserts in the western states makes for lesser speeds imho.

The skill level of average the drivers to anticipate corrective action at higher speeds also needs consideration.

The vehicles capabilities which vary.

I use to profile grind freeway surfaces for increased traction, ride quality, and wet weather skid reduction.

What this country needs are some German style audobahns! Roads that are smooth and have good guard rails would be perfect for 125 mph cruising!

http://www.graffconcrete.com/preserving-highways.php

[BigJohn]

Originally Posted by John Boothby

Ok, but back in the 50's when the highway system was designed the average auto was way less capable then today's autos. So, what speed would be just as "safe" for auto's of today? Back in the 50's cars did not even have seat belts! poor brakes, less traction, etc. Now Texas has increased some speed limits to 85 from what I hear. I know for a fact that parts of I-15 in Utah has been increased to 80mph. So, could this be a movement to increase speed limits to a level more up to date with modern auto technology? Just think'n, ya know.

In the late 60's - early 70's I-15 was 85 in Utah.
My 1938 Chevy will do 90.
Who needs seat belts??

[XfireZ51]

Originally Posted by BigJohn

In the late 60's - early 70's I-15 was 85 in Utah.
My 1938 Chevy will do 90.
Who needs seat belts??

Don't need a seat belt till you're headed for the windshield.

[John Boothby]

Could you imagine a high speed freeway (Autobahn) from L.A. to NY City! 3 thousand miles of wide-open road!! Include a separate divided parallel road for truck traffic.