Grade Signs and What They Mean

Dec 5, 2017

Take a short drive just a few hours east or west from the Northwest Adventure Rental office and you will find some of the most beautiful mountain ranges and scenery in the world. With the Olympics on one side and the Cascades on the other you are bound to find a sign warning of a steep grade.

When you first see these bright yellow signs they can seem a bit cryptic and mysterious, but they are actually very simple and extremely useful to RV drivers. In simple terms- grade is the amount of rise or drop in a given distance. For example: a five percent grade would mean that the road is going to rise or fall five percent over the next 100 feet. In a more specific example: if a sign says 5% downgrade next four miles, this means you will descend 1,056 feet over the next four miles. This is how we got to that number: there are 5,280 feet in a mile multiply that by 4 to get 21,120 feet and multiply that by .05 to get the five percent grade.

Grade Signs and What They Mean

Luckily you don’t have to do all that math in your head when you see a road grade sign to decipher if the grade is going to be steep. When a grade is 5 percent or greater you will see signage to make you aware. Law prohibits U.S. Interstates from having grades higher than 6 percent, however on other roads and non U.S. highways there is no limit. What RV drivers really want to be cautious of is stretches of road with long grades. The longer the grade, the more care should be taken. A short length super steep grade into the double digits may seem more intimidating, but a long grade of only 5 percent can do a number on your brakes if you are not driving properly.

When driving over a lengthy grade there are a few techniques to employ. Going uphill, keep an eye on how the engine is operating. You might want to switch off the air conditioner when climbing a hill to keep the engine cool. Watch the temperature readings and if you have one, keep an eye on the transmission temperature gauge as well. If you see a rise in temperature release the throttle a bit and downshift. Follow this procedure if the engine seems to drag a bit as well.

Going downhill requires a lot of steady patience to keep the RV under control. Slow and steady wins the race here. Remember this old trucker’s phrase when driving down a sizable grade “ You can come down the hill too slow many times, but you can come down the hill too fast only once.” This also applies to RV drivers. It is always always always better to start out slower than you feel you should go because downhill momentum is going to begin to build and if you start too fast it is easy too lose control quickly. A good rule of thumb is to remember what gear got you safely up the hill and use that or a gear lower to come back down again. "Diesel engines will have more effective/actual compression braking whereas gas engines only have grade shifting by using the transmission to reduce speed, much less effective than a true compression/exhaust brake that Diesel engines provide." - David Izbicki

The gear you use for downhill grades should sustain your RV at a comfortable speed and not feel like you are on the edge of rushing down the hill. Some truck drivers use an aggressive braking method that can work for driving an RV as well. It works like this: keep the vehicle with the right gear and find your safe speed when the RV is at that speed bear down on the brake until you are five miles an hour below it. Now release the brakes and do not touch them again until the vehicle reaches that safe speed. You should never continuously ride the brakes this will burn them out.

Navigating road grades in an RV is not as intimidating as it seems with the right technique. For more great RV information and RV rentals please browse or site or contact us anytime.