Well built paths and trails attract more people who want to walk, ride their bikes and otherwise get active. Poorly built paths are unsuitable for bike riding or soon become unrideable as the path degrades. Poorly built paths discourage people from riding.
What’s the problem?
Some paths are built with rough or slippery surfaces that are dangerous and uncomfortable for riding. Bike riders will avoid these if possible and they will not encourage more people to ride. Poorly built paths soon become unrideable as the path degrades.
What are the risks?
The most common risks of a poorly built path are:
rough or slippery surfaces that can cause a bike rider to fall. For instance: unstable gravel paths are slippery, especially on curves; rough joints can deflect bicycle tyres;
unstable or rough edges of the path which can cause a crash if a rider swerves to avoid another path user. This is often caused by grass or other vegetation growing into the path, or the edges of the path collapsing due to inadequate foundations;
crashes due to the path surface degrading over time. For instance erosion ruts or potholes that can catch a rider’s wheel. Erosion ruts running parallel to the path on a downhill section are especially dangerous. Poor camber or drainage of paths and inadequate foundations are common causes of degradation. Heaving of path sections due to tree roots or expansion of the path surface (especially concrete) can cause dangerous ruts and ridges;
crashes in poor light as a person rides off the edge of the path due to poor demarcation of the path. This can include poorly defined edges; dark coloured paths and/or lack of linemarking;
crashes due to riders falling over their handlebars if their wheel gets caught in soft shoulders of a path;
crashes due to riders falling over the edge of the path when the shoulders have not been built up the path level leaving a dangerous step or ledge.
Bike riders will avoid rough or slippery paths if possible. See below for example of low path usage on a tourism trail due to poor path surface.
Poorly built paths may be cheaper to build initially but the overall lifetime costs can be substantially higher due to higher maintenance costs or the need for remedial treatments or reconstruction.
What is the solution?
Build paths to an appropriate standard suitable for the existing foundation conditions. These standards are well established. Initial construction costs savings for low quality paths will usually be surmounted by the increased cost for reconstruction, upgrade and maintenance of the path.
concrete paths provide a longer lasting, smooth and non-skip surface that is visible in low light and are usually preferred by bike riders (see VicRoads report at right). They have a higher initial construction cost and care needs to be taken with providing smooth construction joints (saw cut, not trowelled) to allow expansion and contraction of the path without heaving or cracking. Concrete paths should be broomed or hessian dragged finished before hardened to provide a non-slip all-weather surface - this is best done perpendicular to the direction of travel
asphalt or flexible pavements also provide a smooth, non-slip surface but a shorter life-span. They are more suitable for use on expansive (clay) soils which move with moisture absorption. Asphalt paths are susceptible to edge degradation often due to grass and other vegetation. Use of concrete edging can reduce this and also helps demarcation of the edgeo of the path, especially in low light, but adds substantially to the initial cost. Their aggregate size needs to less than 10mm and spray seal aggregates less than 7mm
unsealed paths (gravel, earth, lilydale topppings etc) have the lowest initial cost but may only be acceptable for the first stage of development of a path or to preserve the path alignment. Care needs to be taken to avoid erosion of the path which can cause dangerous ruts and potholes. Raising the path above the surrounding ground level and “crowning” the path may help reduce degradation and erosion. Unsealed paths are not suitable on slopes as they erode too easily.
Bicycle Network Victoria recommends using the AustRoads Guide specifications combined with those for skid resistance, roughness, texture from the VicRoads performance based specification. Note that the VicRoads report tested comfort and safety of riders over several thicknesses of sheeting and found that anything over 15mm high for a step perpendicular to the direction of travel is unacceptable (as opposed to the 20mm in the AustRoads Guide see wording at right)
Above table from Cairney and King 2003 (VicRoads report by ARRB)
Table adapted from 2005 report for Australian Bicycle Council. Note costs are a guide only and now dated. Constrained sites will have higher relative costs.
What do the guidelines say?
The Austroads Guide to Road Design – Part 6A: Pedestrian and Cyclist Paths provides extensive guidance on the construction of paths for cycling.
Under “Construction and Maintenance Considerations for Paths” the guide states: “If bicycle paths are not adequately constructed and maintained, cyclists are not likely to use them, or may swerve in order to avoid surface irregularities thus creating a hazardous situation.
“Smooth, debris free surfaces are a fundamental requirement for riding bicycles in safety on paths, and on all roads, from freeways to local streets … a rough surface or pothole can cause a cyclist to fall, leave the path and crash or come into conflict with other path users.”
“In order to gain an appreciation of the problems faced by cyclists with respect to maintenance it is suggested that road maintenance supervisors should ride a bicycle over sections of road commonly used by cyclists. This enables a more detailed examination of the surface to be made including problems that are easily missed from a motor vehicle.
“A substantial capital investment is often made in providing bicycle paths and jurisdictions' authorities should also have an effective management regime to define responsibilities and to ensure that these facilities are adequately maintained.”
The Guide provides some detailed path cross sections that may be used to guide the specification of paths – see bottom of this page.
What does Bicycle Network Victoria say about the guidelines?
The Guide is clear on the need for a smooth, debris-free surface for cycling and the need to build and maintain path to an adequate standard. It is also clear on the tolerances for defect in the path surface.
They do not however provide a specification of skid resistance or guidance on how many defects per length of path is acceptable.
The VicRoads report on a performance based specification for a bicycle facility covers these issues and also provides a user based review (mostly male) of some path surfaces.
The performance-based specification recommends:
no vertical displacements greater than 15mm based on feedback from people riding over differing thickness sheets of timber (as opposed to 20mm in the Road Design Guide);
a skid resistance greater than 60 (as measured by the pendulum test) for path.
It also provides recommended specifications for both asphalt and concrete path for roughness (measured by Walking Profiler) and texture (measured by sand path test).
The irony is that the state government, having received the report, proceeded to let a tender for a cheaper, substandard path with a rough chip seal surface. The path had to be resurfaced within a year following complaints from path users. See this page on the Federation Trail.
Any examples, good and bad?
When Banyule City Council and VicRoads were upgrading the Main Yarra Trail in the Warringal Park area they chose to use a coloured concrete to be more sympathetic with the surrounding environment.
This ensured that a high quality path could be built in keeping with the aesthetic concerns of stakeholders.
The contrast between this path and bitumen can be seen in this photo (right), which also illustrates a good road crossing treatment.
The Gardiners Creek Path is ashpalt with a concrete edge 200mm deep. The edge defines the edge of the path, which is helpful for bike riders in low light. It also helps reduce encroachment of weeds and grass onto the path surface and reduces maintenance costs to council - albeit at a higher initial cost.
Example of poor path surface from the VicRoads report on performance criteria for paths. This path in Werribee was rated as unacceptably rough by riders. Path users will tend to use the verge of the path rather than put up with the discomfort of the path itself. The aggregate size is greater than 7mm as recommended in the AustRoads Guide to Road Design.
The Koonung Creek Trail alongside the South Eastern Freeway in Melbourne has been built with a gravel surface. The surface is loose and slippery and on slopes dangerous ruts have developed that could catch a bicycle wheel and cause a crash.
Trail Surface and Economic Benefit
The High Country Rail Trail is a spectacular trail following the shores of Lake Hume and offers a fantastic ride between Wodonga and Old Tallangatta. This difference in surface directly influences which sections riders choose to use and the amount of tourism spending in local businesses.
These figures, based on a recent economic study, show that the higher capital cost of sealing a trail will be quickly repaid by increased use and tourism spending. Whilst these direct economic tourism benefits may not be available to communities in urban areas, the distinct message from riders is that they prefer a sealed path please!
The 21km trail between Wodonga and Tallangatta is unsealed and not suitable for bikes with narrow tyres.
Unsealed path attracts only 15% of riders.
The 21km unsealed section of trail attracts an estimated 35 users per week, which could generate up to $8,000 in tourism spending per week.
The trail then continues for 6km east of Tallangatta to the abandoned town of Old Tallangatta. This section is sealed and is enjoyable on all types of bikes.
The sealed section of the path attracts 85% of riders.
The 6km the sealed section has had 175 users counted per week and could generate up to $45,000 in tourism spending over the same time period.
Diagrams from Austroads Guide to Road Design - Part 6A: Pedestrian and Cyclist Paths