If you’ve ever driven in an area with hills or mountains, you might have seen a road sign that warns of a steep grade. While the signs usually measure grade in terms of percent, they’re actually giving information about the angle of the hill. If the road rises at too steep an angle, trucks and other heavy vehicles may lose control, causing accidents.
Why It Matters
On most highways, grades are limited to 6%. That means the hill can’t be at more than a 3.4 degree angle. However, some mountains have angles as steep as 8%, or a 4.6 degree angle. While these angles seem pretty small when you measure them with a protractor, they can cause big problems for heavy trucks driving at high speeds.
If a downward slope is at too steep an angle, the truck can lose control and start rocketing quickly toward the bottom of the hill. If the upward grade is too steep, a heavy truck might not have enough power to climb it. Long distance truckers must learn how these steep angles affect their vehicles. They develop strategies for driving over steep grades.
See for yourself: http://www.youtube.com/watch?v=766O8QxYcGw
Learn more about steep grades and how they are handled by drivers and bikers.