Bicycle Network: Good Design Guides
Hills, Gradients & Slopes
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- slope, hill, gradient, hills, path, drop off, underpass, culvert, steep
Steep grades are a barrier and potential hazard for bike riders. Riders build up speed on steep descents and may have trouble stopping or staying in control. This may lead to serious crashes. If a hill is too steep, riders will look for a way around. Grades over 5% are only acceptable for short distances. Remember: Not too steep!
What’s the problem?
Steep slopes are a danger for bike riders going downhill, especially inexperienced riders who may have trouble stopping safely. They are also a barrier for riders going uphill. Longer slopes should be 2% or less in grade. Grades over 5% should be avoided and only used if necessary over short distances. Slopes combined with sharp bends and/or sharp drop offs, especially at the base of the slope, are particularly dangerous.
What are the risks?
On steep slopes path users could:
- Build up too much speed going downhill and not be able to stop to avoid hazards or other path users. This can result in serious injury especially if a rider falls off a drop at the bottom of the slope; hits an obstacle; or falls over trying to negotiate a sharp corner at the bottom.
- Not be able to ride up the hill and be forced to walk their bike or take a long detour to negotiate the route. People pushing their bikes take up more width than those riding - this can cause a blockage or hazard for those riding downhill.
What is the solution?
Keep cycling grades as flat as possible. Avoid slopes greater than 5% grade where possible.
If steep slopes must be used, for instance to negotiate a road crossing or beside waterways then:
- Lengthen the slope to reduce the grade. This can often be done by cutting into the hillside at the top and extending the ramp or run up at the bottom of the hill ;
- If longer sections of steep path need to be used consider providing intermediate flat sections (or landings) for people to recover control of their bikes on the downhill or their breath on the uphill;
- Keep the path as wide as possible; avoid path-side obstacles and leave plenty of run off room for people to “bail out” if necessary. This is especially important at the bottom of the slope;
- Avoid hard obstacles or drop offs at the bottom of the slope which can cause serious injury if the rider hits or falls over them. Riders are especially susceptible to riding over a ledge or drop off which can cause them to fall over the handlebars and injure their neck;
- Avoid sharp corners at the bottom of the slope which are hard to negotiate if the rider is going fast. A corner at the base of a slop also reduces the chance to build up speed if riding up the hill;
- Keep sight lines clear so people so people can see how steep the slope is; how long it is; where it leads; any other people using the path and any obstacles.
The base of the slope is critical as it is where the highest descent speeds are likely to occur and the potential site of the most serious crashes. People also tend to gather at the bottom and top of hills to wait for others or prepare themselves for the climb (or catch their breath and admire the view). Leave as much room as possible at the base of the slope. Enhance sight lines (including lighting), path surface and width and path alignment as much as possible.
What do the guidelines say?
The Austroads Guide to Road Design – Part 6A Pedestrian and Bicycle Paths makes it clear (in section 7.4 on gradients) that steep slopes are a barrier and potential hazard for not only bike riders but pedestrians and those with mobility impairments (e.g. those in wheelchairs). The guide states:
“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%.
“Figure 7.1 shows the maximum lengths of uphill travel acceptable to cyclists. The figure is bases on a review of the ease of uphill travel (Andrew O’Brien & Associates 1996).
"In using the figure designers should understand that:
• Above 3% the acceptable length reduces rapidly and it is considered this is the desirable maximum gradient for use on paths. However, in practice there are cases where it is not feasible to achieve a 3% maximum and the designer has no choice but to adopt a steeper gradient.
• In cases where 3% cannot be achieved consideration should be given to limiting gradient to a maximum of about 5% and providing short flatter sections (say 20m) at regular intervals to give cyclists travelling both uphill and downhill some relief from the gradient.”
The section on pedestrian path surface treatments is also relevant as it shows the requirements for people walking and those with mobility impairments including those in wheelchairs. Hand rails and intermediate landings may be required on slopes on shared paths that are likely to be used by people who have trouble walking. The use of hand rails may impinge on the usable path width and this should be taken into account when designing the width of the path.
Where it is not possible to avoid steep grades consideration may be given to provision of stairs with wheeling ramps to allow bike riders to push their bike up the stairs rather than carrying it. Consider though, that may people cannot get up stairs with their bikes, even if stairs have wheeling ramps - for instance older people, children or people with young children in child seats. Section 11.4 of the Guide states:
“Where it is not possible to locate a path for cycling so that an acceptable gradient is achieved a bicycle wheeling ramp (figure 11.4) may be provided to accommodate a significant change in level over a short distance.
"Wheeling ramps should be used as a last resort and should not necessarily be regarded as a treatment that serves the needs of cyclists well. They can be unsatisfactory to recreational cyclists (i.e. carrying children) as for commuters (due to inconvenience). They are generally regarded as inappropriate where used in association with new path facilities if alternative access is possible.
"Existing stairs can often be readily modified to provide for cyclists by the addition of a ramp formed by concrete infill or steel plate. Ramps may be either on the sides or within a median of the stairs.”
The Guide goes on the provide details on the design of wheeling ramps (sometimes called Chinese wheeling ramps). See figures from the guidelines at the bottom of the page.
What does Bicycle Network Victoria say about the guidelines?
We agree with the Austroads guide's advice on avoiding steep gradients and what to do if you cannot avoid a steep hill.
The guide however, provides limited advice for downhill travel on what the limits of acceptability are for slopes of different lengths and gradients. The only advice comes in figure 7.1 which deals with the difficulty of uphill travel. There is no similar advice on downhill travel apart from the following in the Commentary:
"It has been suggested (State Bicycle Committee of Victoria 1987) that ‘many existing bicycle facilities have gradients which require riding skills beyond those of most recreational and child cyclists when they are riding down the grade. As a guide, a grade greater than 10% over 50m with horizontal curves or a gradient of 12% over 50m on a straight path is considered to be extremely hazardous.
"It should be noted that grades of 10% or greater are difficult for cyclists to ascend and may be avoided by recreational and novice riders."
Guidelines from the US gives clearer guidance and might be more useful. The American Association of State Highway and Transportation Officials' (AASHTO) 1999 Guide to the Development of Bicycle Facilities gives the following guidance on grades of paths:
Grades on shared use paths should be kept to a minimum, especially on long inclines. Grades greater than 5 percent are undesirable because the ascents are difficult for many bicyclists to climb and the descents cause some bicyclists to exceed the speeds at which they are competent or comfortable. On some shared use paths, where terrain dictates, designers may need to exceed the 5 percent grade recommended for bicycles for some short sections. As a general guide, the following grade restrictions and grade lengths are suggested:
- • 5-6% for up to 240 m (800 ft)
- • 7% for up to 120 m (400 ft)
- • 8% for up to 90 m (300 ft)
- • 9% for up to 60 m (200 ft)
- • 10% for up to 30 m (100 ft)
- • 11+% for up to 15 m (50 ft)
Grades steeper than 3 percent may not be practical for shared use paths with crushed stone or other unpaved surfaces for both handling and drainage erosion reasons.
Options to mitigate excessive grades:
- When using a longer grade, an additional 1.2-1.8 m (4-6 feet) of width to permit slower speed bicyclists to dismount and walk may be considered.
- Provide signing that alerts bicyclists to the maximum percent of grade.
- Provide recommended descent speed signing.
- Exceed minimum stopping sight distances.
- Exceed minimum horizontal clearances, recovery area and/or protective bike rails.
- When possible, use a wider path [1.2-1.8 m (4-6 feet) addition recommended] and a series of short switchbacks to contain the speed of descending bicyclists
Any examples, good and bad?
A steep hill down to the creek level from Heidelberg Rd Bridge level on the Merri Creek Path. The slope is steep and has a bend at the bottom with a 0.5m drop off. There is a real danger of people losing control of their bike and riding over the edge of the drop off and breaking their neck.
Protected vegetation on the river bank restricts the options for flattening the slope.
One option is to realign the path on the opposite bank and install a bridge.
A steep hill at Lily St, Essendon West. The gradient of the slope has been reduced through long switch backs. This has greatly lengthened the route length but allows riders to negotiate the gradient. Warning signs erected at the bottom and top of the Lily St hill (insert).
Even at the reduced gradients the long slope length allows high speeds to be attained downhill but sight lines are clear and there is plenty of room at the bottom of the slope to recover control.
The ramp up to Flemington Bridge overpass, Flemington.
An old ramp is used for the popular Capital City Trail. Hand rails installed on both sides of the ramp to meet Disability Discrimination Act requirements to aid people in wheelchairs etc negotiate the slope.
Unfortunately the rails have narrowed the usable space and make it hard for bike riders to pass each other or other path users.
|Eel Trap Bridge, Docklands.
Built on the remains of the Webb Dock Rail Bridge this bridge has been hailed as an architectural marvel. For bike riders though, its like Paris Hilton - looks good but doesn't work.
When designing this shared path bridge the designers failed to take into account the grade which required the installation of hand rails in the centre of the path to meet the DDA requirements. These hand rails reduce the usable width and bring path users into potential conflict. They are also a hazard in themselves especially the central rail with its vertical poles that can catch pedals, and the low wall.
If the bridge design had allowed a longer slope and gentler gradient these may not have been necessary .
|Gipps St Bridge Steps.
These steep steps are a barrier for many people.
A long running campaign has been running to replace these steps on Melbourne's premier cycling path. The steps and wheeling ramp were erected to negotiate a steep slope up to a bridge crossing of the river.
|Manningham St Bridge steps.
These steps have wheeling ramps on both sides and a central hand rail. Notice the groove in the ramps to help guiding the bike wheel up the slope. These steps still exist but a bridge over Manningham St means the path is now accessible to all path users - see below. Notice at the top of the steps the path slopes upward to reach the height of the bridge deck so the steps are just spanning the last section of the slope.
The ramp up to the Manningham St Bridge.
The ramp up to the bridge deck faces the steps shown above on the opposite side of the road.
A long slope has been broken by intermediate landings (notice the stepping of the hand rail which follows the slope) that allow riders to regain control on the downhill or regain their breath on the uphill.
Figures and Table below from Austroads Guide to Road Design Part 6A: Pedestrian and Cyclist Paths