Bicycle Network: Good Design Guides
Fences and Barriers
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- fence, fences, barriers, clearances
A fence or barrier may be needed for paths running alongside a steep batter, drop off or other hazard. Fences should not be a hazard themselves - they should present a smooth surface that cannot snag a bike or rider and avoid sharp edges that could cause injury. Fences alongside paths should be 1.4m high (1.2m min.) and set back at least one metre from the edge of the path (0.5m min.).
What’s the problem?
Fences and safety barriers built to prevent falls can themselves cause crashes if not designed and positioned correctly. Fences can snag pedals, handlebars or rider’s bodies. They are an example of path-side obstacles – see lateral clearances.
In the example at right a person on a bike clipped the low bluestone wall and crashed, face first onto the stanchion support of the road safety barrier causing serious injuries. The council responsible for the design of the path was taken to court and forced to pay damages to the injured.
What are the risks?
When deciding whether to erect a fence or safety barrier beside a path, an assessment must be made of the risk of crash without the barrier versus the risk of crash with the barrier installed. Any assessment of risk should take into account the potential severity of a crash, but just as importantly the likelihood of the crash occurring.
Fences and barriers can be a hazard in themselves and can narrow the useable width of a path making a crash more likely. In Melbourne there are many kilometers of straight or gently curving sections of path with no safety barrier along creeks and rivers next to steep slopes. The reported crash rate along these sections is negligible. Fencing and barriers are best reserved for sections of path where serious crashes are more likely.
The major risks from incorrectly designed or located fences or safety barriers are:
- crashes of single riders if they hit the fence or “snag” the handlebars, pedals or a part of their body, especially vertical elements including the ends of the fence
- collisions or close calls between bicycle riders and other path users travelling too close to each other to avoid fencing that is too close to the edge
- riders crashing into or onto a fence or barrier placed too close to the path – sharp elements can cause serious injuries if hit
- bike riders falling over a low safety barrier or fence and falling onto the ground below, potentially head first, and injuring their neck or spine.
These must be weighed against the risks from not providing a fence or safety barrier. These include:
- path users falling off the edge of a path, potentially head first over the handlebars, and injuring their neck or spine
- crashes of single riders riding who ride off the path and into a hazard. Examples include riding into a ditch and crashing head first, down a slope where they loose control or onto a busy road.
See also the pages on lateral clearances and boardwalks and bridges.
What is the solution?
Provide fencing along paths only when needed. Weigh up the risk of falling into the fenced hazard against the risk that may arise from narrowing the path “user-envelope” by erecting fencing alongside the path. If fencing is needed make sure it is not a hazard to path users. Any fencing or barrier alongside a path should be designed to make sure it will not snag the bike or the body of a rider.
Leave as much clearance to the fence or safety barrier as possible – at least 1.0 m (0.5m min.) though 0.3m is acceptable if space is constricted and the fence presents a smooth face to path users.
What do the guidelines say?
The guidelines (see extracts at right) state that fences are desirable where:
• “there is a steep batter or large vertical drop located in close proximity to the path
• the path is adjacent to an arterial road and it is necessary to restrict cyclist access to the road
• a bridge or culvert exists on a path
• a hazard exists adjacent to a particular bicycle facility
• cyclists are likely to be “blazing a separate trail’ at an intersection between paths or around a path terminal.”
Many paths run alongside waterways and fences may be needed for certain sections:
“A fence barrier may be appropriate where a path is located adjacent to a watercourse or lake. A full barrier fence would be appropriate where a vertical fall to water occurs within 5m or a path.”
Fences should be high enough to prevent a bike rider falling over the top.
“The recommended height for fences (desirable 1.4m and minimum 1.2m) …The minimum height of 1.2m should be used only where the severity of the hazard is considered to be low. A higher fence (e.g. 1.6m) may be considered where the fence is protecting path user from a severe hazard (e.g. high vertical drop from a structure to a body of water or rocks).”
Fences and barriers adjacent to roads have particular requirements.
The Austroads Guides (Part 6B: Roadside Environment) also list requirements for fences for cyclists.
“The width of path and lanes should also account for the presence of fences and reference should be made to the Guide to Road Design – Part 3: Geometric Design (Austroads 2009a) for details of required clearances. The following types of fence should not be used in close proximity to bicycle lanes or paths. They should be located at least 1m from the edge of bicycle facilities and preferably should be much farther away:
• Treated pine log – these are often constructed with exposed ends and are invariably too low to be used adjacent to bicycle routes.
• Chain mesh – these may catch pedals, have exposed elements (e.g. bolts and nuts, loose wire) and in some instances have been responsible for spearing injuries.
• Post and wire – these have exposed elements.
Irrespective of the type of fence used, the main requirement is that adequate clearance is provided between the edge of the path and the fence. More guidance on the need for fences adjacent to paths and clearances is provided in Austroads (Guide to Roads Design Part 6A: Pedestrian and Cyclist Paths, 2009g).
It is also very important to provide fences that cater for people who have impaired mobility, particularly on ramps and bridges. Figure 4.9 shows a pedestrian/cyclist bridge with additional rails to provide for people who use wheelchairs.”
What does Bicycle Network Victoria say about the guidelines?
Need for fences and barriers
The guidelines recommend that fence barriers are appropriate where a drop off greater than 25cm high occurs within 5m of the edge of the path (full barrier for drops more than 2m and partial barrier for drops 25cm to 2m). On many paths alongside creeks and waterways this would mean continuous full safety barriers for long lengths of the path. In Melbourne this is not the case where long sections of path run within 2m of significant drop offs or steep slopes with no safety barrier fence. There has not been any reported evidence of increased crash or injury rates in these locations.
In practice barrier fences have been only provided in higher risk sections where other factors contribute to the risk of a crash. These include:
- downhill sections of path and/or curves
- narrow paths and/or high path usage which leaves little room for manoeuvre
- slippery of bumpy path surfaces (e.g. wooden boardwalks)
- unclear or blocked sight lines meaning the path cannot be seen and a drop off might be unexpected.
Design of fences and barriers
The full and partial fence barrier designs provided in the AustRoads Guides (figures 7.5 & 7.6) include vertical elements to the design that could snag the body of a bike rider or their bike. This is especially true if the fence barrier is located within 0.5m of the edge of the path.
A more suitable design would eliminate the risk of snagging bike riders and might comprise fine mesh panels (in metal or other inflexible material) between the vertical elements. There are some current examples of fences that come close to achieving this. We have attempted to take the most promising elements and proposed a concept that would meet the requirements of path users (see pictures below).
One common problem with fence barriers on slopes is that the hand rails, required for disabled access provisions, are attached by diagonal supports. These diagonal supports are usually at a height that could catch bike handlebars and cause serious crashes if a rider is pulled off balance. If the hand rails were attached via horizontal supports this would eliminate this problem. DDA requires a 270° around the top surface of the handrail so the attachment must be made at the base. See Australian Standard 1428.1-2009 Design for Access and Mobility. Handrails must be 865-1000mm from the path surface. Note that handrails are only required on sloping paths.
Any examples, good and bad?
|This bridge over Manningham St has mesh panel fences topped with a handrail. A good result except for the low height of the fence which should have been 1.4m and the brackets of the hand rail would have been better if horizontal so that snagging of a handlebar would be eliminated.|
A concept design of a fence that would meet the requirements of the guideline and be acceptable for path users. The fence is 1.4m high with mesh panels between, and flush with, the vertical elements providing a smooth surface that cannot catch or snag a bike or rider. Note that the first segment is angled back (splayed) from the edge of the path an additional 200mm to reduce the risk of riders running into the end element of the fence. Splaying back also help increase the visibility of the fence to oncoming riders and should be done for at least the last 1000mm. The hand rail (position shown 865 to 1000mm from path surface for DDA requirements) is only needed for disabled access if the path is on a slope. The supports for the handrail do not extend below the handrail itself so cannot snag the handlebars of a bike (DDA requires a hand grip for 270 degrees on the rail) Other DDA requirements: The hand rail must extend 300mm from the end of the fence; a kerb rail 150mm is needed that is not set back more than 100mm from the hand rail and a hand rail would be needed on the opposite side of the path.
Since the fence is smooth the set back from the edge of the path can be reduced to 0.3m if needed. Mesh panels allow a view of the area behind and allow light onto the path both which help improve the amenity of a path.
|The William Barrak bridge over the Flinders St rail yards has excellent flat panel fences complemented with a handrail at the required height for disabled users. A very good result except for the brackets supporting the hand rail (circled) which would have been better if set horizontally so that snagging of a handlebar would be eliminated. The design above tries to remedy this.
The height of the fence at 1.2m is the minimum recommended and adequate for the situation - the bridge is wide, smooth and flat so the risk of a crash into and over the fence is low. Some panels are clear Perspex which works well too to open up the views of the surrounding parkland.
This safety fencing on the Moonee Ponds Creek Trail is of correct height and has a hand rail for the disabled. Unfortunately the many vertical elements may snag handlebars although the clearance of the order of 40cm compensates and decreases the chances of a rider hitting the fence.
An example of a full barrier fence - see Fig 7.6 below.
This safety fencing on the Moonee Ponds Creek Trail is of correct height and has a hand rail for the disabled. Unfortunately the many vertical elements may snag handlebars and the lack of clearance by fixing the fence on the path increases the danger of a rider hitting the fence.
The end element is especially hazardous and the upper joint presents a sharp edge that could injure path users.
The open panels also could allow a child to fall through the fence.
Federation Trail bridge over Werribee River shows clean smooth surfaces and a good safe height of fence. Highly recommended. If on a slope a hand rail would be required and in fitting this, the support brackets should be horizontal to avoid snagging of handlebars.
Note the yellow bollards. The middle bollard has been removed to allow vehicle access. The bollards should be taller and highlighted with linemarking - see page on middle of path obstacles.
On the Eastlink Trail architectural elements seem to have priority over practicality with unfriendly vertical metal strips forming the fences. The risk of injury to a rider impacting the vertical slats has been partly remedied by the placement of the 2 horizontal pipe rails although the diagonal supporting brackets can still catch the handlebars of a bike.
The safety fence is well placed on the outer edge of the concrete ramp so as not to reduce the effective path width.
On the Yarra Trail in Abbotsford near the Convent this safety fence has been designed with concave supports so as to minimise snagging of handlebars of a wayward rider. The top rail (at approx. 1.2m) is adequate considering the low risk of injury in the event of a rider going over the top.
The well spaced horizontal wires would be inadequate in a higher structure with greater danger but here children would be expected to be under supervision. The wires also allow open views of this natural environment.
The supports for road safety barriers can present a hazard for path users. At this site on the Bay Trail at Black Rock a person on a bike hit the bluestone edging of the path and fell, face first onto the Armco barrier stanchion support. He sustained serious injuries. The council, which was responsible for the design and maintenance of the path, was found liable damages to the man.
The guard rail here on the Outer Circle / Anniversary Trail at Hartwell has been protected by a fence made of recycled plastic planks. The design developed by Replas and the City of Boroondara gives greater protection to cyclists by overlapping the top of the steel support posts.
The risk of hitting the support posts and their sharp edges is removed but the fence is still too low - a path users hitting this fence is likely to fall over the top and risk falling head first onto the road and sustaining serious injury.
Figures and extracts below from Austroads Guides - see panel information
Extract from Table 4.1 from Austroads Guide to Road Design Part 6B: Roadside Environment (2009)