Bicycle Network: Good Design Guides

Lateral Clearances (Obstacles too Close to Paths)

Rate:

Comment
lateral clearances, clearance, obstacles

Obstacles too close to the edge of a path can pose a significant hazard for path users. At least one metre of clear space must be left each side of a path so that people do not run into obstacles or each other. The minimum safe vertical clearance for a bike rider is 2.5m.

What’s the problem?

Obstacles too close to the edge of paths cause a hindrance and hazard to bike riders. There is a history of serious crashes caused by such objects and judges have found councils liable for damages where they have allowed hazards to be installed or to remain next to a shared path. Fences and barriers are a particular problem.

What are the risks?

The major risks from objects too close to the edge of a path are:

crashes of single riders if they hit obstacles or “snag” the handlebars or pedals;
collisions or close calls between bicycle riders and others due to them having to travel closer to each other on the remaining usable path width;
crashes or near misses from people not being able to see each other, or hazards, on the path;
crashes between path users and people/animals stepping unseen onto the path from behind a screen;
a perceived (or real) risk to personal safety, especially at night, as trees and shrubs can provide hiding places for would-be attackers.

What is the solution?

Leave at least 1m clearance each side of the path as a “shoulder” or verge where people can ride off or stop if needed without crashing.

Paths should be designed using an “operating design envelope” which allows for the safe use of the path with included minimal lateral clearances to obstacles. The "operating design envelope" includes the actual path width plus 1m of clear space each side. Objects can then be placed an appropriate distance outside this envelope. For a 3m wide this equates to a 5m wide envelope. The clear space each side of the path should be a path shoulder that is rideable but not necessarily as smooth or solid as the path itself (eg grass or compacted gravel).

Larger clearances are needed for some obstacles such as trees whose branches can block views or whose future growth will impede the path. Entrances to buildings should also be set back further from the path.

Of particular concern are obstacles which can snag the handlebars or pedals of a bike or which can injure someone hitting or falling onto them. Common snag hazards include vertical bars or elements of fencing alongside paths, particularly the end elements of fences and barriers. “Softer” objects can also pose a hazard as tree branches and vines can snag handlebars or pedals.

If objects alongside the path are unavoidable, for instance when a path travels alongside a building, or alongside a fence barrier to a drop off, then they should present a “smooth” surface to the path users and avoid elements that would snag the bike or person riding it. Objects at head, handlebar and pedal height are particularly hazardous. The Austroads Guide to Road Design (Part 6A) refer to a minimum lateral clearance of 0.5m where obstacles with “smooth features” “align parallel to the path”. This can be dropped to 0.3m only in exceptional circumstances ("provided the design and end treatments are appropriate, or where extenuating circumstances exist").

Sometimes paths are retrofitted into existing spaces, for instance along railway lines, and only minimal space is available. In these cases where there is little clearance either side of the path, measures need to be taken to make the path as safe as possible. This means maximizing sight lines and path width and removing or modifying remaining obstacles so they are clearly visible and unlikely to cause a crash. If modifying walls or buildings to create smooth surfaces, keep the path as wide as possible. Adding rails can sometimes reduce the path width by up to 40cm which negates the safety effects by forcing riders closer together.

Where the path curves, larger clearance to objects alongside the path are needed to maintain sight lines so people on the path can see potential hazards and each other. Path design and maintenance of path side vegetation should allow path users to see 30m of the path ahead. This allows them to see other path users and slow down (or stop) if necessary.

Obstacles too close to the edge of the path also can reduce perceived personal safety by providing places where potential assailants can hide and await potential victims. This is especially true of unlit paths in quieter areas such as alongside creeks or railway lines.

What do the guidelines say?

The guidelines refer to 1.0m recommended, and 0.5m absolute minimum lateral clearances between the bicycle operating envelope and objects beside the path. A less clearance should only be used where safe and where unavoidable.

p72, Section 7.7.1 – Clearances: “It is important for safe operation that adequate clearance is provided between bicycle operating spaces for cyclists travelling in opposite directions and between the cyclist operating spaces and potential hazards beside paths (e.g. fixed objects, vertical drops, steep batters).

The following guidelines should be applied for clearances between the cyclist operating spaces and potential hazards beside paths:

Where both the areas beside the path and the path alignment are both relatively flat a lateral clearance of at least 1.0m (0.5m absolute minimum) should be provided between the edge of any path and any obstacle, which if struck may result in cyclists losing control or being injured. However, on high-speed paths it is most desirable to have a clearance considerably greater than 1.0m;
Where it is considered that a hazard beside the path has attributes that could cause serious injury to cyclists (e.g. sharp surfaces such as the rear side of the posts and rails or steel W-beam road safety barrier), designers should assess the risk of cyclists losing control of the particular section of path, and consider either increasing the lateral clearance or shielding cyclists from the hazard. Depending on the situation a rub rail behind the posts or a cyclist fence near the edge of the path could be provided;
Where a vertical drop or a steep batter exists or must be provided adjacent to the path the guidance in Section 7.7.2 should be applied.
Obstacles beside paths include bushes, culvert end walls, trees and large rocks used in landscaping. Provided the design and end treatments are appropriate, or where extenuating circumstances exist, a lesser clearance may be acceptable for fences and other obstacles that have smooth features and are aligned parallel to the path (0.3m absolute minimum).

These horizontal clearances are partially illustrated in Appendix A.
The minimum vertical clearance required by cyclists is 2.5m, measured above the riding surface (also shown in Appendix A) (sic – actually in Figure 4.7, section 4.2.2). This applies to tree branches, underpasses, doorways, sign structures and any other overhead structure."

Figure 5.1 (below) gives examples of clearances from a shared path to obstacles within a road reserve.

What does Bicycle Network Victoria say about the guidelines?

The guidelines do not place enough emphasis on designing paths with an “operating design envelope” that incorporates rideable shoulders on each side that allow riders to safely “run off” the path if needed.

Though the guidelines refer to operation envelopes for bike riders and the need for space each side of riders, the emphasis is on provision of lateral clearances to other path users and objects immediately alongside the path.

The new guidelines refer to a recommended 1.0m lateral clearance with 0.5m “absolute minimum” which is an improvement on the old 0.3 m absolute minimum that tended to become the default in tight situations. The lesser 0.3m clearance is only allowable where obstacle are "smooth features and are aligned parallel to the path" where "extenuating circumstances exist."

The result should be an improvement in the design of paths which, at times, have been designed allowing only for the minimum path width and minimum clearances to obstacles.

Any examples, good and bad?

Trees/ Vegetation


St Georges Rd path, Northcote (at about Melways 30, D6) Pathside vegetation has overgrown the path making it hazardous for path users. The right and centre photos show the vegetation growing over the path. At right, a bike rider has to ride in the centre of the path to avoid palm branches. At centre, bushes grown over the edge of the path reducing its usable width. The palm to the left blocks views of any traffic at the intersection. The photo at left how the path newly built. Notice the bushes alongside the path have been set back almost 0.5m. Newly planted they do not block the path but have quickly grown across the path. They should have been set back at least 1.5m to allow for future growth.

Fences


Examples of fences that are hazardous to bike riders. At left the Main Yarra Trail at Mary St (ramp on right, Melways 2M, B2) the fence has been erected right up to the edge of the path on the path corner and leaned over the path. Not only does this reduce the usable path width but the vertical pole of the fence could snag on bicycle pedals. The fence could have been set back from the path. In centre, the Moonee Ponds Creek path at Dean St (Melways 29,B8) the top part of the fence intrudes on the path and can catch handlebars. Also, anyone crashing into the end piece of the fence is likely to be injured. At right the Bay Trail in Hobsons Bay has wooden bollards along the edge pose a hazard to path users. Not only have they been place on the edge of the path but have since loosened in the ground and lean over the path itself. They are likely to catch on bike pedal and are likely to injure anyone falling on them.

Boardwalks

The fencing along the Bay Trail at Middle Brighton Baths is much better. The fence is set back from the edge of the trail and curves so that the top rail is smooth and at handlebar height. There is little chance of snagging pedals or handlebars. The full width of the path is still available on this boardwalk section.

Confined Areas

Upfield Path, Brunswick. Before and after replacement of fence. The old wooden fence was built on the edge of the path. The new steel fence was set back about 30cm from the edge and reduces the crash risk on the path. The verge of the path beneath the fence needs to be reinstated to the level of the path to remove the lip that could still cause crashes from wheels being deflected. The wall at left also needs a smooth surface as the vertical pillars can catch handlebars and cause a crash. A wooden board 30cm high at 1.0 to 1.3m height would be one solution.

Signs

Often signs or temporary structure are placed too close to the edge of paths. Here the portable traffic hazard sign is over the path and the sign itself is at head height.

The following are pictures of the figures mentioned in the excerpts of Austroads Part 6A at right

Lateral Clearances - AustRoads Guides Text

Excerpts from AustRoads Guides

AustRoads Guide to Road Design - Part 6A: Pedestrian and Cyclist Paths (2009)

Page 21

4.2 Cyclists
4.21. Principles
In relation to path and road engineering all cyclists have six basic requirements whenever they ride:
• Space to ride
• A smooth surface, free of debris
• Speed maintenance
• Appropriate sight lines to path surface
• Connectivity
• Information

These requirements apply equally on roads and paths. By implication the important objective of a safe environment for cyclists must exist, given the provision of space to ride, a smooth surface and the ability of cyclists to maintain their speed, objectives which are reflected in the principles of the path user requirement for pedestrians (see Section 4.1).

Space to ride
Where data is available (e.g. census information and jurisdictional surveys) the space required for new major bicycle paths should be based on an estimation of the likely demand for cycling on the proposed facility. However, where such information is not available the bicycle design envelope and clearances shown in Figure 4.6 proved the basis for design of the bicycle facilities described in this guide. It is important for designers to understand the basis of the design, including clearance requirements, so that they can make appropriate judgements in constrained situations where knowledge of minimum cyclist space requirements is needed. The envelope is relevant to the design of lanes on roads, off-road paths and bicycle parking facilities (refer to AS 2890.3).
The 1.0m wide envelope allows for the width of a bicycle and for variations in tracking. Not all bicycle riders can steer a straight line and when riding uphill experienced riders work the bicycle from side to side whilst the inexperienced may wobble. Bicycle riders also need adequate clearance to fixed objects and to passing vehicles in addition to the 1.0m envelope.
In some situations it may be appropriate to provide for alternative forms of pedal cycles in the design of facilities. For example, it may be appropriate on heavily utilised recreational paths to allow for the space (e.g. width, length, swept path) required by a bicycle trailer that is commonly used by parents to tow young children.
…
Sight Lines
It is important that appropriate sight lines are provided between a cyclist’s eye height and pedestrians to assist in minimising conflict, and between a cyclist’s eye height and the path surface so that cyclists can stop in the event that a hazard exists on the path (e.g. mud deposited during inundation, potholes due to washouts, broken glass, and fallen tree limbs).
Designers should therefore resist the temptation to proved curves that are smaller than necessary (e.g. to create an artificially winding path for aesthetics or urban design reasons). It is much better for safety of path users if larger curves with greater sight distances are provided. Sight distance for cyclists is covered in Section 7.8.
…
4.2.2 Cyclist Operating Space and Clearances
The concept of a cyclist operating envelope (Figure 4.6) and clearances (Figure 4.7) may be used to construct the appropriate width of facility required for cyclists under various conditions. The envelope is assumed to be consistent over the range of operating conditions and allowance for higher speeds is provided through larger clearances to both other cyclists and fixed objects beside the path. Appendix A provides guidance on how the envelope and clearances are applied to particular situations in order to determine satisfactory operating widths.

Page 48

7.7 Clearances, Batters and Need for Fences
7.7.1 Clearances
It is important for safe operation that adequate clearance is provided between bicycle operating spaces for cyclists travelling in opposite directions and between the cyclist operating spaces and potential hazards beside paths (e.g. fixed objects, vertical drops, steep batters).
The clearance between cyclist operating spaces varies according to the type of use and operating speeds as follows:
• on paths designed for commuting and major recreational activity a minimum lateral clearance of 1.0m is required between opposing bicycle operating spaces because of the high relative speed which exists when cyclists approach one another from opposite directions at speeds of 30km/h or more (i.e. closing speed of 60km/h)
• on recreational paths where the speeds of cyclists are not likely to exceed 20km/h a minimum lateral clearance of 0.4m is necessary between opposing bicycle operating spaces.
Consideration should be given to the provision of a centreline on all two-way paths that have minimal clearance between opposing flows in order to provide guidance and certainty regarding the opposing travel path.
The following guidelines should be applied for clearances between the cyclist operating spaces and potential hazards beside paths:
• Where both the areas beside the path and the path alignment are both relatively flat a lateral clearance of at least 1.0m (0.5m absolute minimum) should be provided between the edge of any path and any obstacle, which if struck may result in cyclists losing control or being injured. However, on high-speed paths it is most desirable to have a clearance considerably greater than 1.0m.
• Where it is considered that a hazard beside the path has attributes that could cause serious injury to cyclists (e.g. sharp surfaces such as the rear side of the posts and rails or steel W-beam road safety barrier), designers should assess the risk of cyclists losing control of the particular section of path, and consider either increasing the lateral clearance or shielding cyclists from the hazard. Depending on the situation a rub rail behind the posts or a cyclist fence near the edge of the path could be provided.
• Where a vertical drop or a steep batter exists or must be provided adjacent to the path the guidance in Section 7.7.2 should be applied.
Obstacles beside paths include bushes, culvert end walls, trees and large rocks used in landscaping. Provided the design and end treatments are appropriate, or where extenuating circumstances exist, a lesser clearance may be acceptable for fences and other obstacles that have smooth features and are aligned parallel to the path (0.3m absolute minimum).
These horizontal clearances are partially illustrated in Appendix A.
The minimum vertical clearance required by cyclists is 2.5m, measured above the riding surface (also shown in Appendix A) (sic – actually in Figure 4.7, section 4.2.2). This applies to tree branches, underpasses, doorways, sign structures and any other overhead structure.

7.7.2 Batters and Fences
General
The installation of a fence at the side of a path used by cyclists is 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.
Steep batter or vertical drop
Figure 7.4 provides a specific recommendation for the provision of a fence on a path in close proximity to a steep batter or vertical drop. In addition to those referred to in the figure, other circumstances may exist where it may be desirable to erect fences even if provision is not required by the figure (e.g. curving path alignment, located in the vicinity of batters or a drop-off, bridges).
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.
Figure 7.4 highlights the circumstances in which either a partial fence (refer to Figure 7.5), or a full barrier fence (refer to Figure 7.6) or equivalent form of protection should be used. These barriers are intended to prevent access to a slope or to a fall away from a path or other riding surface, where injury might otherwise be expected in the event of a cyclist riding inadvertently off the line of a path. Examples of these fences are provided in the Guide to Road Design – Part 6B: Roadside Environment (Austroads 2009g).
The recommended height for fences (desirable 1.4m and minimum 1.2m) is illustrated in Figure 7.5 and Figure 7.6. 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 sever(e) hazard (e.g. high vertical drop from a structure to a body of water or rocks).
Similar or even more stringent measures may be required adjacent to roads. Where a batter or fall is located in close proximity to a road, designers should have regard for the requirements of Figure 7.4, particularly where no kerb exists at the edge of a road. However, the actual measures required should be decided upon with consideration of all road users and of the particular circumstances.

7.8 Sight Distance
For safe travel cyclists must be able to see across the inside of horizontal curves, under overhead obstruction in sag curves (e.g. where a path passes under a road) and over vertical crest curves to a sufficient distance to enable them to stop or take evasive action if necessary to avoid another cyclist, a pedestrian or an obstacle in their path.
Figure 7.7 gives stopping sight distances required to enable a cyclist to stop for various combination of bicycle operating speeds and gradients. The table is based on a coefficient of friction of 0.25 and a perception/reaction time of 2.5 seconds. The eye height of the cyclist is assumed to be 1.4 metres and the object height is assumed to be zero to recognise that impediments to bicycle travel exist at pavement level (e.g. potholes or stones).
Paths should be designed and constructed to provide the greatest sight distance possible at any given location.
The stopping sight distance to be used in the geometric design of paths should be at least equal to that shown in Figure 7.7, and in particular should be used:
• for intersection design;
• in setting out the alignment of paths;
• in relation to the position of terminals and handrails;
• at entries to underpasses;
• for landscaping in the fields; and
• otherwise as required to ensure the safety of path users.
All two-way bicycle paths should be designed to provide a sight distance between opposing cyclists (i.e. as shown across a horizontal curve in Figure 7.8) at least equivalent to twice the stopping sight distance given by Figure 7.7. This is to ensure that cyclists who are overtaking can avoid a head-on collision.
Path sight distances can be drastically reduced by the growth of vegetation and hence their maintenance is critical to safe operation.
Figure 7.8 illustrates the relationship between stopping sight distance, radius of the curve and the lateral clearance to significant visibility obstructions such as extensive vegetation or an earth embankment. Isolated features including trees do not necessarily constitute a significant obstruction of cyclists can see most of the curve beyond them.
Whilst the graph is provided by use by engineers, it is suggested that it (or a simple tabular representation) should be supplied to works staff to be used in construction and routine maintenance operations. (figures referred to above are exacting guides in the determination of sight distance requirements, in many instances it may be convenient to seek a minimum sight distance of say, 30 metres. Such a dimension could be provided to works staff to be used to assess the need for routine maintenance operations and the like.)
Where an existing path is narrow, the level of use of a path is high (such that cyclist may be expected to travel in both directions across the width at coincident periods i.e. ‘non-tidal flow), and widening is not feasible (because of physical or financial constraints), it is recommended vegetation should be set back as shown in Figure 7.8. This set back is to prevent the possibility of head-on crashes. If such a set back is not possible then consideration should be given to any one or a combination of the of: (it may be desirable in some instances to calculate lateral clearance on horizontal curves based on the sum of the stopping sight distances for cyclists travelling in opposition directions around a curve. Where such provision is impractical, on or a combination of the following may be appropriate:)
• local widening of path around the curve;
• warning sighs
• tactile lines.
A vertical curve should join all changes of grade. Crest vertical curves must be of sufficient length to give the cyclist the stopping sight distance shown in Figure 7.7. Where practicable, sag curves should be the same length as equivalent crest curves to ensure comfort and an aesthetically pleasing path alignment (good appearance). Figure 7.9 shows the minimum length of vertical curve for various changes of gradient and design speeds.

VicRoads Cyclenotes

VicRoads also provides some guidance in their Cyclenotes no. 3 on shared path design: Shared bicycle pedestrian path design.pdf