1.1 Sustainable Safety

The principle of functionality is that the design which is fit for purpose is safer. Urban streets, roads and spaces are always multi-functional.

The functions are either movement or place related. It is important therefore that the designer understands and accommodates the functions applicable to the particular scheme.

The lists below offer an aide-memoire to typical functions encountered in urban areas. Bear in mind that functions can vary at different times of the day or week, e.g. bus lanes, parking weekends etc

Movement Related Functions (inter alia)

• Pedestrians – walking, crossing
• Cycling
• Vehicular traffic (all modes)
• see Road Classification Section 1.6, Traffic Management Guidelines http://www.dto.ie/traffic_manual.pdf
• Drop-offs and pick-ups
• Access to property
• Turning
• Abnormal vehicle manoeuvres
• Parking of vehicles and bicycles
• Bus stops – waiting and crossing to and from the bus
• Loading and delivery
• Refuse collection

Place Related Functions (inter alia)

• Housing and access
• Parks and open space
• Communication and information points
• ATMs and postal services
• Meeting and gathering
• Play and recreation
• Shops including window display
• Social and community services
• Shelter and public convenience
• Heritage and architectural value
• Services (gas, water, sewerage etc.)

The principle of Homogeneity is that reducing the relative speed, mass and directional differences of different road users sharing the same space increases safety. This has a beneficial impact on the level and severity of accidents that might otherwise occur.

Where the relative speed, mass or direction is not homogenous, different road users may need to be segregated.

Relative Speed: As average cyclist speeds are 15 to 20 km/h, designers should pay particular attention to vehicular traffic exceeding 50km/h

Relative Mass: In general, bicycles should not be positioned close to large vehicles. Bicycles are however frequently permitted within bus lanes where there is generally consistency in speed and diection, and the bus driver has been trained in relation to driving with cyclists..

Relative Direction: The most common directional issues occur where drivers turn left across cyclists or right across opposing cyclists, and when cyclists weave across traffic lanes. While these movements cannot be precluded, they must be accommodated in a controlled, low speed and legible manner.

In summary, consider the following:

• The current or proposed mix of transport modes
• The relative speed profile across the transport modes
• The likely changes of direction or crossing movements to be catered for

The principle of Legibility is that a road environment that all road users can read and understand is safer. A legible design will be self-evident, self-explanatory, and self-enforcing. Legibility is equally necessary in both mixed and segregated cycling environments, and is not therefore simply about lane markings and streaming traffic.

A legible road environment is such that:

• all potential conflicts are obvious and the resolution of the conflict is mutually understood by all road users.
• all road users know where to position themselves, e.g. cyclists “taking the traffic lane” or using a dedicated lane or track.
• all road users are instinctively aware of the expected position and likely behaviour of all other road users.
• potential hazards can be identified in advance
• road users can communicate visually with each other
• road users can understand in advance the route they have to negotiate

Design considerations

• Ensure that each mode is properly positioned?
• Ensure that the urban design and layout communicates the desired behaviour to all road users
• Ensure there are no contradictory messages within the layout
• Ensure the legibility is effective at night and in poor weather

The principle of Forgivingness (Passive Safety) is that environments that contribute to benign outcomes of accidents are safer.

Consider in particular:

• Falling: Should a cyclist lose balance or tumble, nearby traffic should have sufficient time and space to stop
• Evasion room: Non traffic areas could be used for evasion, e.g. grass verges
• Cross falls: Slope cycle tracks away from the traffic
• Physical hazards: Remove guardrails, protruding street furniture, gullies etc.
• Lighting: Higher level of illumination where cyclists are positioned

Design Considerations

• What are the risks to vulnerable road users?
• How forgiving are the principal conflict points?
• Does the accident database support this view?
• What information / training do road users need?

The principle of Self-Awareness is that where road users are aware of their own abilities and limitations to negotiate a road environment, the environment is safer.

Consider in particular:

• Provide a higher Quality of Service close to locations where cyclists are less experienced or more limited, e.g. school children, parents with cycling trailers, tourists with panniers etc.
• Alternative routes within the vicinity that match reduced ability
• Site specific information and signage
• Training for inexperienced users
• Peak and Off-Peak – is the cycling challenge more difficult at different times of day or week?