Steep slopes can be a barrier and potential hazard for not only bike riders but pedestrians and those with mobility impairments (e.g. those in wheelchairs). So we thought it might be useful for planners and advocates to look at a map showing which roads are steeper than others.
The Gradient Map displays average slope for a road segment and have been classified as follows:
- Less the 3% Grade (ideal for attracting novice riders)
- 3% – 5% Grade (attracting novices becomes increasingly difficult above 3% – see below)
- Above 5% Grade (should not be provided unless unavoidable – see below)
The Austroads Guide to Road Design state: “As a general principle longitudinal gradients on paths should be as flat as possible. The potential hazard for cyclists due to high speeds on steep downgrades is as important as the difficulty of riding up the grade when determining maximum gradients on two-way paths.”
“Gradients steeper than 5% should not be provided unless it is unavoidable. It is most important that sharp horizontal curves or fixed objects do not exist near the bottom of hills, particularly where the approach gradient is steep (greater than 5%) and relatively straight. If a curve must be provided at the bottom of a steep grade then consideration should be given to providing additional path width, and a clear escape route or recovery area adjacent to the outside of the curve.”
The guide states that uphill travel is difficult for bike riders and cites a study and figure which indicates that riding becomes increasing difficult at grades above 3%. (ref: https://www.bicyclenetwork.com.au/general/for-government-and-business/2864/)