Need for a safety barrier
Pedestrians or cyclists may require shielding by a road safety barrier in situations where they are considered to be exposed to a higher than normal risk of being struck by an errant vehicle. Where a pedestrian/cyclist facility either exists or is proposed for an existing site that has a run-off-road crash history an assessment of pedestrian, cyclist and bystander exposure should be undertaken so that crash reductions for alternative treatments can be considered.
For new works, the protection of pedestrians and cyclists from passing traffic may also be
considered and should be investigated by undertaking a risk assessment to assess the likelihood of the encroachment of errant vehicles into proposed pedestrian/cyclist facilities.
When considering the need to protect pedestrians and cyclists at a site the designer should consider the combination of factors that would require shielding of the facility including the:
number and type of path users (e.g. whether large numbers of people congregate in or pass
through the area, the presence of primary school children)
factors that make the site more hazardous than other sites along the road (e.g. road
geometry and characteristics that would increase the risk of run-off-road events)
type of traffic that may cause a run-off-road event to be particularly severe (e.g. high
numbers of heavily laden freight vehicles).
Situations where a road safety barrier may be appropriate are:
intermediate and high-speed roads where a path is within the clear zone
Treatment options
A road safety barrier is also a hazard to motor vehicle occupants and if located closer to the road has a higher probability of being impacted by errant vehicles. Where practicable the preferred options for treatment are:
design and management of the road to minimise the likelihood of encroachment into the
roadside by motor vehicles
location (or relocation for existing facilities) of the pedestrian bicycle facility away from the
road where it has a low probability of encroachment by errant vehicles
provision of a road safety barrier (where installed to protect bystanders consideration should
be given to it being placed closer to the bystanders rather than the road in order to minimise the potential for vehicle impacts).
Cyclists and pedestrians may require a barrier to prevent them inadvertently running onto a traffic lane from an adjacent shared path (e.g. footpath on a bridge with high numbers of young
pedestrians/cyclists). In cases where there is no need to protect path users from errant vehicles, or errant vehicles from roadside hazards, a pedestrian fence of a suitable height for cyclists should be adequate.
Design considerations
Where there is a need to provide a road safety barrier between a path and road traffic it is important that the rear of the road safety barrier is not a hazard for pedestrians and cyclists. Designers should ensure that:
adequate clearance is provided between the rear of the road safety barrier and the path
(refer to the Guide to Road Design – Part 6A: Pedestrian and Cyclist Paths) (Austroads 2009g)
no sharp edges, burrs or other potential hazards (e.g. protruding bolts) exist
where sufficient clearance cannot be provided, cyclists are protected from ‘snagging’ on
posts by the provision of suitably designed rub rails
where sufficient clearance cannot be achieved, consideration is given to the need to increase
the height of the barrier either to prevent errant cyclists from falling over the barrier and into a traffic lane or to discourage pedestrians from jumping over the barrier to cross the road at an unsafe location.
Where sufficient space is available, a frangible pedestrian fence may be erected behind the road safety barrier at a distance that would accommodate the likely deflection of the barrier under impact by an errant vehicle. Adequate clearance is also required between pedestrian fences and bicycle paths and shared paths. In situations where space is restricted, it may be necessary to consider provision of a higher rigid barrier.
Designers should ensure that any modification or attachments to a barrier would not be detrimental to its performance under vehicle impact or result in components being hazardous to motorists or path users in the event of a crash with the barrier (e.g. horizontal rails spearing vehicles).
Separate rails may be provided to meet these requirements provided they do not have the potential to spear through an impacting vehicle, create debris that poses a serious hazard, or change the characteristics of the system to the extent that crash outcomes are significantly altered.
Pedestrian and cyclist access through barriers
Preferred practice is to avoid providing breaks in a road safety barrier. However, it may be
necessary to consider breaks at locations where pedestrians cross the road and where breaks are necessary, barriers may be overlapped and/or safe end treatments must be provided.
Bridges and overpasses
AS 5100.1 – 2004 provides information on barriers for bicycle and pedestrian bridges and for some design elements for bicycle/pedestrian paths as they relate to bridges.
Temporary barriers and roadworks
During roadwork activities, consideration needs to be given to provision of bike and/or pedestrian access through the works and temporary barriers may be required to provide protection with respect to road traffic and construction traffic. Other situations where provision of temporary barriers may be required include during special events where there is a need to physically control both vehicle and pedestrian movements.