4.3.1 It may be of value to the non-riding road designer to briefly explain how motorcycles are different:

Surface grip and consistency

4.3.2 Motorcycles have a much greater need for a consistent and high coefficient of friction from the road surface than twintrack vehicles, especially on wet surfaces and in areas requiring braking and steering.

Riders adopt an angle of lean to negotiate a corner that is related to speed and bend radius - any change in grip between tyres and surface can destabilise the machine.
Any deviation from a consistently level surface in the same areas can seriously impair the motorcycle’s road-holding ability.

A sudden change in surface level rapidly loads and unloads the suspension, thus reducing the grip between front wheel and road surface. In other words, the wheel rebounds upwards and in severe cases can lose contact with the surface.

Unpredictable changes in the road environment that call for rapid deceleration or braking while cornering can cause the motorcycle to”sit-up” and take a tangential line away from the bend.

Bends

4.3.3 There is anecdotal evidence that riders who are losing control of their machine on a bend tend to “fixate” on what seems to be the object in their path most likely to hurt them - typically a tree or signpost.

The argument goes that, once this “target fixation”occurs, the rider will usually hit that object. Whether or not target fixation is a genuine phenomenon, research indicates that a significant percentage of motorcycle fatalities (17% in GB in 2003) involve collision with road side objects (unpublished DfT STATS19 data, see also ATSB 2000, quoted in MCC 2002).

Wherever possible, any highway furniture or signage should not be positioned on the outside of bends, creating a “clear zone” in higher speed rural situations, to minimise this problem.Other options are:

Visibility

4.3.4 Drivers often do not “see”motorcyclists because of the relatively small frontal area presented by their machines, the presence of other road vehicles and roadside obstructions. Junction design should ensure that drivers do not have their sight lines obscured.

Rural roads

4.3.5 The higher speed potential on rural roads, especially those that are attractive to leisure riders, means that many of the aspects covered in this section have greater importance for casualty reduction on these roads.

Safety barrier

4.3.6 Research in Australia has shown that the probability of a falling rider being killed doubles in a collision with safety barrier systems. Injuries were less severe from impact with the beam or the face of a concrete safety barrier system, compared to collisions with the posts used in the system or the roadside posts being protected by the safety barrier (Gibson and Benetatos 2000). Falling riders, as they slide along the road surface, are most likely to be at risk of added injury from the unprotected barrier support posts and projecting surfaces or by sliding underneath barriers (FEMA 2004).

Riders often express concern at the perceived dangers of wire rope safety fence, but the Government’s Advisory Group on Motorcycling concluded that this form of safety fence appears, from the limited research completed so far, to be no more hazardous than other types of post-and-rail barrier.

There is general agreement that more research is required on the effects of different types of fence on falling riders and on the posts that cause the most severe injuries to riders when they hit safety fence (AGoM 2004).

4.3.7 Pending further research it seems that retro-fitting impact mitigation measures to posts and some means of preventing dismounted riders from passing under rails would improve secondary safety for falling riders in safety barrier collisions. TD 19/06 Requirement for (Vehicle) Road Restraint Systems (DMRB Vol 2 Sec 2) advices designers tthat "at high risk sites it is recommended to use an 'add on' motorcycle protection system to post and rail type safety barrier to minimise the risk of injury to motorcyclists.

Priority junctions and roundabouts

4.3.8 Important considerations at priority junctions and roundabouts are to optimise sight lines and provide good braking surfaces for all users.

This will mitigate the problem of drivers not responding to motorcyclists’ presence - even when the latter have priority.

The relatively small frontal aspect of motorcycles makes this particularly important. Low entry angles on roundabout approaches mean riders in the circulatory area can be obscured by the central pillar on emerging cars. Entry angles that are too high can lead to excessive speed on approach and tail-end collisions.

Wide entries encourage drivers to pull up on the offside of the rider, especially if the latter is on a low-powered machine. Both of these potential problems are mitigated with entry angles between 30° and 40° and entry widths no greater than absolutely necessary - and these measures should also have the effect of reducing entry speed. A balance will need to be struck between capacity and safety.

The positioning of street furniture and vegetation at junctions is critical for good sight lines. A very high proportion of collisions between motorcycles and cars in urban situations are due to emerging drivers failing to see the oncoming motorcycle.

The higher speed of traffic on rural roads requires that designing for adequate sight lines is even more important.

Light Rapid Transit systems

4.3.9 The rails of on-street Light Rapid Transit (LRT) systems can have a destabilising effect on motorcycles and cycles. Ongoing research at Nottingham University into the effects of tram infrastructure on cyclists is awaited.Discussion with recent LRT providers indicates that flush rails with high-PSV surrounding surfaces offer the best compromise between tram utility and the safety of other road users, including riders of mopeds or motorcycles. Seek out the experience of earlier LRT projects such as Manchester, Sheffield, West Midlands, Nottingham and Croydon.

Design Points

4.3.10 To reduce the need for sudden variations in steering or braking and to minimise the consequences of any loss of control, consider these points:

•	Consistent horizontal alignment - for example avoiding bends that tighten after entry - minimises the need for change of steering angle, and hence angle of lean, especially in a critical situation, such as a road surface compromised by water, detritus or leaf fall. Chapter 8 deals with vertical and horizontal alignment in the specific circumstances of traffic calming. Chapter 9 looks at this issue in a Road Safety Audit context.
•	Cross-sectional design consistent with the speed of the road and the radius of the bends.This is more of a problem for roads that have”evolved”over time, rather than new-build, but adverse camber or inadequate super-elevation can be a problem for all motor vehicles, but with worse consequences for motorcyclists.
•	Wherever possible a motorcycle should be able to brake and stop while upright, travelling in a straight line and on a consistent grip surface. Clear and adequate sight lines to pedestrian crossing facilities minimises the need for last minute reactive behaviour. This means keeping formal crossing facilities away from bends where possible and where pedestrian desire lines permit.
•	Consistent skid resistance, including that of extra surface features, such as coloured patches. This is especially important on bends, given the rider’s need to vary position across the lane to maximise safety and provide maximum forward visibility.
•	Use high friction surfacing at junctions with a history of drivers emerging against priority into the path of motorcyclists. This maximises the rider’s chances of braking safely.
•	Terminate high friction surfacing on straight sections. Sudden changes in road surface properties on bends and at junctions, especially skid resistance, can lead to stability problems as the rider tries to cope with the sudden change in the dynamics and response of the motorcycle.
•	Avoid using different surfaces, for example granite setts, to emphasise a change in circumstances, at turning points such as priority junctions and small roundabouts where motorcycles may be destabilised by their use.
•	Thermoplastic markings rarely have the same skid resistance properties of the surrounding road and their skid resistance deteriorates faster than the road surfacing. Arrows and destination markings on bends or roundabouts are of concern to riders as the motorcycle may be leaning over or may be accelerating or braking. Consistent and informative advance warning and direction signs should minimise the need for such surface signing. Careful thought should be given before using large areas of hatching.
•	Specifications for and positioning of in-road and roadside furniture, including impact characteristics when struck by a fallen or sliding body. The principle should be to minimise the number of obstacles, especially on higher speed bends, and to use supports that do not shear off leaving jagged or sharp remnants or that have protrusions that could snag a fallen rider. On higher speed roads consideration must also be given to the swept path of the rider leaning into bends, something that is not of concern for twin track vehicles.
•	Gentle changes in vertical alignment to minimise potential for loss of tyre adhesion and to optimise drainage, both of which have a greater effect on motorcycles than on twin track vehicles.
•	Allow for the higher eye level of riders when positioning street furniture or planting vegetation, especially at junctions. Consider the full growth of trees and shrubs, along with leaf fall characteristics and maintenance.
•	Where it is absolutely necessary to use kerbs in rural areas, use battered kerbing to minimise potential injury to a sliding body.
•	When redesigning an existing layout consider the position and level of utility covers, especially on bends and within braking or steering areas. Avoid forcing riders to over-run them whenever possible. If it is unavoidable, use covers with a skid resistance similar to the surrounding road surface.
•	Consistent signing along a route so that rider expectations are met. This links to the concept of ‘self-explaining roads’, where the level of signing and marking is proportionate to the severity of the hazard and this proportion is the same along the whole route. If the road can “deceive” then warnings are required - a tightening radius or a horizontal deviation immediately over a crest are examples where advanced warning is appropriate.
•	Consider the role that probable future levels of maintenance of the design may have on continued safety. Avoid including design features that require higher levels of maintenance than the road is realistically going to receive, which could in turn lead to future safety problems.