The rise or fall of the grade divided by the distance over which the rise or fall is measured. This calculation yields a decimal figure which is then multiplied by 100 to obtain the percent grade. The percent grade is important in evaluating the proposed slope of a parking lot, driveway road or other passage route, because the steeper the grade, the harder it will be to use or traverse. Too steep a grade can make a roadway hazardous or impassable especially in regions that are prone to receiving snow or ice. A heated driveway system may be appropriate yet difficult to install in steep grades due to the added stress or stretching of the snow melting cables. Contact a Warmzone consultant for installation guidelines.