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Author Topic:   Highway Towing: Maps with Grade Information
jimh posted 11-06-2009 09:27 PM ET (US)   Profile for jimh   Send Email to jimh  
I have done some searching for this information, but never found it. Are there any maps available that show highway routes with information about the grades? By this I mean highway maps that show the steepness of the grade of the ascent and descent of hills or passes on the route?

I believe that there are some standards for maximum grades on interstate highways in the U.S., but I have never seen any maps with annotation of the grades. I would be most interesting to know if such information was available.

Without a map with the grade information, I have been doing route planning using GOOGLE EARTH. I look at the surrounding terrain and make a judgement about the highway grade.

David Pendleton posted 11-06-2009 09:57 PM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
Every state I've driven through over the years publishes a "Truck Operators Map."

These document low bridges, weight restrictions, width restrictions, etc. as well as the nice-to-know stuff like rest areas.

Here's yours:,1607,7-151-9622_11033_32060---,00.html

Curiously, none of the ones I've used offer percent grade information.

I've worked in the trucking industry twice over the years and I still have some contacts. I'll see what I can find out.

Lil Whaler Lover posted 11-07-2009 07:30 AM ET (US)     Profile for Lil Whaler Lover  Send Email to Lil Whaler Lover     
jimh, it is a maximum of 6% allowed on an interstate highway. Try googling "maximum grade on an interstate highway". Rather long but some interesting links. If speciality maps are available this may get you close to them.
Are you a member of AAA? Years ago they would provide Trip-Tics (sp?), and adjust the route somewhat if you told them you were towing a trailer.
K Albus posted 11-07-2009 07:37 AM ET (US)     Profile for K Albus  Send Email to K Albus     
Here's a link to an easy-to-use website for planning bicycle trips that will allow you to plot grade changes over a specific stretch of highway.

It seems to work pretty good for short stretches of road, but gets a little quirky for long stretches.

jimh posted 11-07-2009 10:30 AM ET (US)     Profile for jimh  Send Email to jimh     
Thanks for the information about the maximum grade allowed on interstate highways, although I did not see any sort of reference cited or a link to where one could find that stated by the proper authority. Suggesting that one ought to make a search for information is not the same as providing a link to the information, and if there is a source of information, it is really best to give a link to the source of the information, rather than to suggest that such information could be found if one searched. As I mentioned, actually in the first sentence of my article, I have already done some searching for information I am seeking and not found it. The information I am seeking is a source of maps that might show where there were grades and what the grades were in the interstate highway system.

My thanks to Dave with his pointer to the Michigan Department of Transportation website. As it so happens, I was aware of that resource, and, quite coincidentally, they have an office a few blocks from where I work which I have visited and received some maps, albeit maps that did not show any grades.

Thanks to Kevin for the link to the bicycling website. I tried making a plot, but it did not work as I hoped.

K Albus posted 11-07-2009 11:11 AM ET (US)     Profile for K Albus  Send Email to K Albus     
Jim, there are map books available with the information you are seeking:

Unfortunately, it does not appear that the information you are seeking is readily available online for free.

jimh posted 11-07-2009 12:13 PM ET (US)     Profile for jimh  Send Email to jimh     
Kevin--Thanks for the pointer. The commercial maps looked interesting, and were supported with many favorable reviews. I ordered both maps. I will comment on them after I receive them.
ConB posted 11-07-2009 12:19 PM ET (US)     Profile for ConB  Send Email to ConB     
I recommend a Ford F250 with a Power Stroke diesel for
towing your Whaler.
You will have to look in the mirror to remind yourself you are towing your boat.
With this tow vehicle the steep grades are no worry and will be fun.
The none towing fuel mileage ain't bad either.


Jerry Townsend posted 11-07-2009 01:01 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
Jim - I have a trucker's atlas (compliments of a trucker friend) which has an abundance of information - but does not have the grade information. As such, I suspect the grade information you seek would have to come from a special map.

The 6% grade limit on interstates may be correct - but on non-interstate roads, such as mountain passes, can have grades of 10%. Makes for a slow climb - and a slow decline, and down-shifting (before starting the decline) to use the engine as much as possible to prevent boiling the brake fluid. --- Jerry/Idaho

number9 posted 11-07-2009 03:18 PM ET (US)     Profile for number9  Send Email to number9     
Anybody else notice this in South Carolina?

For some reason on the interstates in SC my vehicles have a difficult time maintaining a steady speed using the electonic cruise control. Typically they would slow 1-3mph up a hill and speed up going down. First noticed on a 1997 Isuzu Rodeo I4, 5 speed manual that I installed the ECC. The same vehicle would maintain speed on much steeper interstate grades in NC and TN. Other vehicles including 2001 Isuzu Trooper, V-6, 4wd, auto, 2001 Ford F-250, 7.3 diesel, 6 speed manual and 2003 Mazda Miata, 5 speed all have done the same thing.

Sounds crazy but what has happened to me on a regular basis.

Wasatch Whaler posted 11-07-2009 07:39 PM ET (US)     Profile for Wasatch Whaler  Send Email to Wasatch Whaler     
ConB is right.

I live at about 7,200 feet elevation. A turbocharged Diesel (and I'm not talking a Volkwagen; think Ford, Dodge or GM heavy duty pickups) makes towing heavy loads up steep grades at high elevations a breeze.

You also have a long wheel base which adds longitudinal stability and typically excellent brakes as well.

At least several times a year I'll tow a trailer weighing about 10,000 lbs. It's no problem.

David Pendleton posted 11-07-2009 11:22 PM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
Jim, a friend tells me truckers can get highway grade info on their in-cab Qualcomm computers which, of course, you have to pay for.
jimh posted 11-08-2009 09:14 AM ET (US)     Profile for jimh  Send Email to jimh     
Dave--I have not been in the cab of a modern over-the-road truck in twenty years, and it sounds like they're quite modernized these days.

As I mentioned above, I ordered the map set that shows grade information. Unfortunately, it does not show any grades in Michigan, but, on the other hand, we really do not have very many steep grades of any length on our highways in Michigan. For the ones we do, I guess I can figure the grade from topographic maps. I do enjoy gazing at a good map, however, and what better way to spend a winter of planning trips than with a good highway map. The samples of the maps I saw looked quite decent, so I have high hopes for the map booklets.

jjandpop posted 11-08-2009 11:00 AM ET (US)     Profile for jjandpop  Send Email to jjandpop     
Try Camping they provide grades for the RV community.
jimh posted 11-08-2009 11:57 AM ET (US)     Profile for jimh  Send Email to jimh     
Your suggested resource is not a fully-qualified domain name.
Buckda posted 11-09-2009 08:05 AM ET (US)     Profile for Buckda  Send Email to Buckda     
Jim -

I'm having trouble recalling, but I thought you pointed a reference to google earth or some other program that showed you the elevation changes on a specified route and allowed you to compare two routes?

I seem to remember having the discussion when talking about your trip to the PNW.

Is that option no longer available, or is it not detailed enough?

jimh posted 11-09-2009 08:43 AM ET (US)     Profile for jimh  Send Email to jimh     
It would be nice if GOOGLE EARTH had that feature. I don't think it does.
Buckda posted 11-09-2009 08:51 AM ET (US)     Profile for Buckda  Send Email to Buckda     
Ok. I will admit it is possible that we had a discussion about how NICE it would be if that option were available...
jimh posted 11-09-2009 09:32 AM ET (US)     Profile for jimh  Send Email to jimh     
Now that Dave has reminded of the potential of GOOGLE EARTH to help in discovering grades, I have to agree, it is useful. In GOOGLE EARTH the elevation of the terrain is shown, and there is a RULER function that allows you to measure distances. You can find the grade from calculating the elevation change on the highway over distance.

For example, I know that there is a substantial uphill grade on northbound I-75 just northwest of the town of West Branch. Using GOOGLE EARTH I found the summit of the hill to be 1,444-feet in elevation. I then moved down the slope of the hill 2,000 feet and found the elevation to be 1,329-feet. The change in elevation was 115-feet in a distance of 2,000-feet. This means the grade is

115 / 2000 = 0.0575 or 5.75-percent

That grade is within the specified maximum of the federal Interstate Highway system design specifications. The design standards of the federal Interstate Highway system are mentioned in a Wikipedia article on that topic at

and the grade is said to be limited to a maximum of 6-percent.

This method is useful if you already know where there are grades and you wish to measure then, but it is a bit tedious to inspect a long highway route. You'd have to be alert for elevation changes and then compute the grades when you found a significant change.

gnr posted 11-09-2009 10:47 AM ET (US)     Profile for gnr    
I'm curious as to the reasoning behind plotting the grades one would encounter while traveling the interstate highway system.

Can it not be safely assumed that any section of the interstate highway system would meet the 6% maximum guideline and be relatively easily handled by pretty much any combination of recreational vehicle and trailer?

Not trying to be a smart a$$. I'm sure there must be a good reason.

It just escapes my feeble mind.


I think the Delorme Topo mapping software that I have makes it relatively easy to determine grade. I've used this feature to get a feel for hiking a new area and for mountain biking a new area.

20dauntless posted 11-09-2009 12:35 PM ET (US)     Profile for 20dauntless    
I70 through the mountains in Colorado is pretty steep...not sure if it has sections that are steeper than a 6% grade, but it certainly is taxing on nearly every vehicle that drives it. Particularly in the summer, when it is in the 80's and you are driving at nearly 11,000 feet. The Glenwood Canyon section of I70 definitely has sharper curves than a normal interstate and a slower speed limit. I'd imagine hauling a Whaler over this section of I70 would be slow going towing any sizable Whaler. On some of the steeper grades I have had my Pilot floored and not been accelerating beyond 75, and this is with a reasonably light load. Our Excursion with the V10 struggled as well.
David Pendleton posted 11-09-2009 07:58 PM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
Can it not be safely assumed that any section of the interstate highway system would meet the 6% maximum guideline and be relatively easily handled by pretty much any combination of recreational vehicle and trailer?

You've never driven I40 between Nashville and Knoxville, have ya?

jimh posted 11-09-2009 09:16 PM ET (US)     Profile for jimh  Send Email to jimh     
There is a difference between running up a 6-percent grade for a few thousand feet and hauling up one for five miles. The duration of the grade is an important factor. When you are hauling a big boat, it is nice to know what's ahead or to be able to plan ahead .
gnr posted 11-10-2009 09:01 AM ET (US)     Profile for gnr    
Actually I have driven 40 through that area. I guess ridden would be more appropriate since I was on my bike. I've also been across Colorado on 70, again on my bike.

There are a few sections of I-89 here in the Green Mountains of Vermont that bounce right up against the 6% grade limit.

I applaud your paying attention to the details jimh. I wish every single one of the big RV driving, trailer towing rigs I had to get around while running every pass from RT 50 south in southern Colorado had planned ahead.

I do think that an appropriately sized tow vehicle should have no problems traversing any interstate highway in the country though.

Have fun. There is NOTHING like a road trip!

Jefecinco posted 11-10-2009 07:29 PM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     
It might be worthwhile to look into USGS Topographic Maps. Try


Buckda posted 01-11-2010 05:20 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Jim -

GoogleMaps now has a path profiler application that can "snap to" roads and provides detailed/graphical evaluations of the elevation changes along your route.

It still doesn't solve the "how steep are the highway grades" question, but provides some useful information. At the maximum zoom, you can combine it with a distance measurement tool to arrive at the gradient (elevation change over distance) between two exits. That should/could help with the few trouble spots/mountain passes that you might be most concerned about along differing routes.

Just some food for thought.


Buckda posted 01-11-2010 05:22 PM ET (US)     Profile for Buckda  Send Email to Buckda     
...and this is the earlier discussion that I mentioned above. I KNEW that I recalled having this "conversation".

David Pendleton posted 01-11-2010 07:29 PM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
Well Dave, it's nice to see that you haven't completely lost your mind...


PeteB88 posted 01-21-2010 09:00 AM ET (US)     Profile for PeteB88  Send Email to PeteB88     
Jim, you will do just fine using the gears and staying off the brakes on down hill grades. Some of those 5-6 percenters can be 5 miles long. Which way are you going? If I-90 there are some big grades Homestake in Montana and Lookout Pass close to Idaho boarder.

On I-80/84 heading into Oregon you'll one near Laramie, WY as I recall and the big daddy Cabbage rolling into Pendleton, OR. Cabbage is a long but scenic 6 miles of 6% grade. I think there are two escape ramps so if you heat up the binders you can ride'er like a bronco until you hit the bailout as long you hold the wheel straight, don't flinch and aim for the ramp.

I have pulled all kinds of loads on those grades, most memorable was fully loaded 1980 Toyota Corolla wagon, including roof top, pulling fully loaded (light stuff) wooden drift boat all the way to Michigan running along with an ice storm all the way the entire length of I80 alone.

Summer in Eastern WA, OR and those areas can get real hot although cooler at higher elevations.

Like I said you will be just fine, I wouldn't worry one bit, just go easy and use the gears. It's true that some of the pitches on secondary roads are pretty steep but you can handle it no problem. I have seen flatlanders hauling huge, eyesore house trailers and 5th wheelers up some of the steepest grades in the west, like up to Windy Ridge on Mt St Helens or over the Sierras.

Let me know if you want trip ideas, I tramped around that country for many years - I would strongly recommend a cruise on Lake Chelan or even Columbia River Gorge - you could easily launch and do a short cruise or even overnight in the boat on your way esp Chelan.

Bon Voyage.

jimh posted 01-21-2010 09:31 AM ET (US)     Profile for jimh  Send Email to jimh     
As I mentioned earlier in the discussion, I ordered the set of U.S. highway maps with notations of grade information from

and said I would comment on them after receiving them.

The set of books are nicely bound and printed, but as maps go I cannot give them very high marks. I was disappointed in the size of the maps, and in the general design of them. I cannot give this product a strong endorsement. A great deal of the information is actually presented in the form of associated text. The maps are too small for my liking, and hard to read. They could be useful for trip planning. Since I very much enjoy the reading of a good map or chart, it is primarily in this regard that I did not experience the pleasure I was hoping to find in this cartographic presentation.

jimh posted 01-21-2010 09:38 AM ET (US)     Profile for jimh  Send Email to jimh     
Pete--Thank you for the advice on how to drive a truck and trailer combination vehicle in downhill grades. Also thank you for your narrative of your experiences in travel over grades with a boat trailer in tow. In this discussion, however, I was looking for information on highway grades of major interstate roads, more so than advice on how to drive over them.
boatdryver posted 01-21-2010 11:04 AM ET (US)     Profile for boatdryver  Send Email to boatdryver     
Jimh, scanning the thread above I don't see the following mentioned, so I'll offer it as a "don't do what I did" comment.

I'm assuming the trailer you will tow has surge brakes.

I towed my 4500 lb Aluminum jet boat/trailer from sea level up over 7200 ft Donner Pass. The 6 litre gas engine with supposed 8,000 lb tow capacity was maxed out on some of the grades and down to 45 mph.

On the 50 mile descent I used the cooled auto trans for braking which worked fine.

BUT, I didn't think about what that would do to the stainless steel disc brakes on the boat trailer. Without giving them a chance to cool, i cooked them. Pads were gone and rotors badly grooved.

In hindsight, I should have let her run in overdrive every chance I had or even pulled over intermittently to let the brakes cool.


PeteB88 posted 01-21-2010 01:07 PM ET (US)     Profile for PeteB88  Send Email to PeteB88     
Jim - I simply love that country out there and miss it everyday even though where we live ain't bad at all. I am sure you will have no problems and respect serious planning and prep. We are hoping to spend 2-3 weeks out there this summer between N Cali, Oregon and WA State. We're working out the plan but will not be hauling a Whaler X country.


Jerry Townsend posted 01-22-2010 12:31 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
Jim - I have a trucker's map - which shows everything! - except slope grades. Given that, I suspect you are not going to find the information you want.

I suspect from what I have seen, but not paying all that attention to it - but the largest slope on the most roads you will be using is about 6 degrees. There are others which have 10 deree slopes, but generally they are NOT on the major highways - for example, Teton Pass across the Idaho/Wyoming border, Loss-Trail Pass north of Salmon Idaho, et al. But the passes on I-90 are a no-never-mind.

Someone commented that they had to slow down to traverse a grade - but that, as you know, is normal. Someone also mentioned the pass east of Laramie Wyoming - and I recall a few examples of that one. Ocassionally, a trucker would be going east into Laramie, try to downshift and miss it (a bit easier a few years ago) and go into Laramie at around 90 mph or faster - and none of them made the 90 degree turn in downtown Laramie and found themselves broken down among Laramie's 6 - 12 sets of railroad tracks (Laramie used to be a major rail hub) or colliding with a railroad car. Fortunately, the interstate bypasses Laramie today.

I have mentioned this before - but, if you have time, put your boat in Lake Pend Oreille (Pond-d-ray) which is a bit north of Couer d'Alene. Pend Oreille is big, deep and very beautiful. The Farragut State Park and nationally used Boy Scout camp are on the south end of Pend Oreille. Years ago, the navy used Pond Oreille in their submarine testing activities - because of the depth.

And a bit north of Pend Oreille is Priest Lake - another big and very beautiful lake.

Surprisingly, I have never seen another Boston Whaler on Lake Cour d'Alene other than mine. ---- Jerry/Idaho

jimh posted 01-23-2010 08:06 AM ET (US)     Profile for jimh  Send Email to jimh     
JimL--Thanks for your narrative of your experience with towing a trailer with surge brakes on an extended down hill grade. Yes, my trailer has surge brakes. I don't think I have ever been on a 50-mile down hill grade.

Jerry--ROGER on the ten-percent grades on secondary roads. I imagine they are not for long stretches. A few years ago we rented a place on Watts Bar Lake, an impoundment lake on the Tennessee River in hilly terrain. We made the mistake of driving down the road that led to the cottage with the boat trailer still attached. We almost did not make it out of there. The hill we had to descend and then later climb was the steepest road I have ever seen, and hauling the boat and trailer up that road put the transmission in our truck to the test.

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