Interstate speeds in various states

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We are in the process of planning our trip out west and I was wondering what speeds traffic normally flows at on the interstates in the following states. In FL, even though the posted speed is 70, normal flow is more like 80 mph.

I am using Microsoft Steets and Trips for planning and it will allow you to enter speeds for the various types of roads (interstates, limited access etc).

The states we will be traveling through are:

GA, AL, MS, OK, AR, TX, NM, AZ, CA, OR, WA, ID, MT, WY, SD, CO, KS, MO, IL, KY and TN.

Your help is appreciated.


I am assuming 70 mph interstate speeds for all of the above listed, if I am in error, please let me know.


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Noticed that you mention WA - patrolled heavily - stay close to their speedlimit on the freeways.

OK inforces their speedlimit, too,

TX you can get away with 10 over and people travel even faster - limited patrolling.

Complete interstate speed limit info is here:
Traffic flow in Texas is usually 7-8 miles over the posted limit, depending on traffic.
My impression on my last drive to Utah and Nevada was that flow was generally a bit faster. This isn't very reliable information, I realize. Maybe you'd should just chill out and go with the flow

RTBRD, when you get out on the open freeways of the west, where there is no congestion, there is no general "flow" to speak of. The trucks usually stick with their speedlimits and most cars do, too or slightly over, so it's hard to give you a general flow pattern for each state that is different that the posted speed.

In TX, there is congested flow between the major cities so it's easier to give you a flow speed, but even that will depend on the traffic conditions.

Some of the states have posted interstate speeds of 75.

When we're planning a trip, we figure an average of 55 to 60 mph which includes the short stops we make for gas and quick meals. If you take longer breaks, plan on about 50mph which is about what AAA gives for time on their triptiks.

The software also gives you the option of putting in rest stops at various intervals and also calculates gas stops.

I am using 15 min. breaks every 3 hours, 17mpg city and 24mpg hiway (this is where knowing your milage and not smiles helps, no option for smiles/mile).

In a state such as CA (driving almost the entire S to N length), if I can use 80 instead of 70 for hiway speeds, that will amount to several hours driving time and will signifcantly change our stopping points. This is why I am interested in the normal flow.
I think that you may be planning this trip a little bit too close!
Are you sight-seeing? How many miles do you think you can handle each day, day in, day out? We usually figure our travel by how many miles we want to put in for the day or where we want to end up and let the hours fall where they may.
That's the nice thing about the software, I can do "what if" real easy.

We are 2 months away and still in the planning process, so things are still somewhat up in tha air. We have the major stops planned but are open to changes.

I'm more or less just trying to get a feel for things. Will we have 2 days for Yellowstone or 3 to 4? Things like that.
In CA, I5 is the main interstate artery from LA north to Oregon and beyond. We have driven part of it from Central CA to San Francisco Bay area recently - posted speed limit 70, but I have kept up with traffic at 80 through this stretch at least. The more scenic and populated Freeway 99 splits from I5 from around Bakersfield to around Sacramento - posted speed limits from 65 to 70 and I usually keep it around 75 no matter what is posted. Hope this helps a little.

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As a general rule of thumb the normal flow of traffic on Interstate 40 in the Texas panhandle is 5MPH over the limit of 70MPH.
But one thing you have to be careful about in Texas is the night speed limit is lowered to 65MPH from 70MPH. So at night 70 is safe but not 75MPH. Again this is only the general rule. You still run across the occassional DPS Officer that will write you up for 2MPH over the limit.

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Posted speed limit in IL is 65. Flow usually around 70 but be careful in construction areas. Generally the roads are too rough to do much faster anyway. Will you be anywhere near Springfield? It is in the center of the state and serviced by I55 and I72.

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Generally 5 mph over will be tolerated by the Highway Patrol in Oklahoma. Interstates (I-40 & I-35) are 70 mph speed limit and toll roads (also part of the interstate system, I-44) are 75 mph. Hopefully by the time you come through Oklahoma the bridge on I-40 that was knocked down by a barge will be repaired. If not, the detour could cost you well over an hour.


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If you want to really enjoy your trip in your new bird, and have the time, avoid the interstate high ways and use secondary roads. In most cases you can find a good road that runs along side the interstate on which you can drive 55-60 mph. You will be amazed at the wonderful things that our great Country has to offer. However, you will not see them on the interstates. When you reach a large city you can use the interstate to get around the congestion. In 1994 we drove from Pennsylvania to Washington State. I think that the only time we were on an interstate was I-90 in Montana or Wyoming for a short distance when the secondary road merged with the interstate. On the way home we followed US 20 from Eugene, Oregon to Chicago. It was unbelievable. This route followed the Oregon Trail. Most small towns had early Western murals painted on the sides of buildings. On our last trips South we followed old Us 17 and avoided I 95. I guess one good thing about being old is that I now have the patience to enjoy the small things in life. By the way, the trip to Washington and back was done in our 1931 Model "A" Station Wagon, over 8,000 miles. Enjoy your trip.
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