9%

A grade is a slope, or the rise over run. It basically measures how steep a canyon, road, or handicap ramp is. This relates to right triangles and tangents. Finding the tangent can find the grade of the slope. Trains have less gradeability (the ability to ascend grades) than cars. On railroads, a steep grade can be a problem. Even a 1% grade could cause the train to be able to pull half of what it could pull on a zero grade surface. So, for grades steeper than 7%, a rack railway is typically used. This helps keep the train on the tracks. When I say a 1% or 7% grade, its just the ratio of the grade multiplied by 100 into a percent. For example: a 0% grade is flat, and a 100% grade is straight up. A 1% grade has a slope of 1/100.