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"Bicycles are...a viable mode of transportation..., both for commuting and recreation." Bicycles can use a shared lane, a wide outside lane, a regular designated bicycle lane, a shoulder or a multi-use path according to the specific context and design requirements. Overall there are six main factors influencing the way bicycles are incorporated in a specific road configuration. The six factors are: traffic volume, average motorvehicle speed, traffic mix or balance, on-street parking, sight distance, number of intersections.
Accommodating Bicycles
Bicycles are recognized by many as a viable mode of transportation in the United States, both for commuting and recreation. Transportation designers should consider the needs of these users in the design of facilities. Basically, there are five types of
bicycle facilities:
Shared lane-a "standard-width" travel lane that both bicycles and motor vehicles share
Wide outside lane-an outside travel lane with a width of at least 4.2 m (14 ft) to accommodate both bicyclists and motorized vehicles
Bicycle lane-a portion of the roadway designated by striping, signing, and/or pavement markings for preferential or exclusive use by bicycles and/or other nonmotorized vehicles
Shoulder-a paved portion of the roadway to the right of the traveled way designed to serve bicyclists, pedestrians and others
Multiuse path-a facility that is physically separated from the roadway and intended for use by bicyclists, pedestrians, and others
There are three primary factors to consider when designing facilities to accommodate bicycles and other nonmotorized vehicles:
1. What type of bicyclist is the route most likely to serve, i.e., advanced bicyclists, basic bicyclists, or children?
Advanced bicyclists are the experienced riders who make up the majority of the current users of collector and arterial streets, wish to operate at maximum speed with minimum delays, and require sufficient space on the roadway shoulder to be treated as vehicles. Designated bicycle lanes along a roadway give riders an even greater degree of comfort along arterial and collector streets. Basic bicyclists and children generally prefer the most comfortable, although sometimes circuitous, access to destinations, using low-speed, low-traffic-volume streets or a separate, multiuse path.
2. What type of roadway project is involved, i.e., new construction, major reconstruction, or minor rehabilitation?
Recommended design treatments are most easily implemented when new construction or major reconstruction is planned. Although retrofit and/or enhancement projects may be relatively limited in scope, opportunities to make at least minor improvements to better accommodate the needs of pedestrians and bicycles should be investigated. Marginal roadway improvements undertaken as part of 3R projects, such as widening the pavement area 0.3 to 0.6 m (1 to 2 ft) will enhance the roadway for bicycle use.
3. What are the current and future traffic operations and design
characteristics of the route that will affect the choice of bicycle design
treatments?
Six factors are recognized by transportation planners and engineers as having the greatest effect on bicycle use:
Traffic volume-higher traffic volumes represent greater potential
risk for bicycles.
Average motor vehicle operating speed-operating speed is more
important than the posted speed limit; motor vehicle operating speed can negatively affect the bicyclist's comfort unless mitigated by special design treatments.
Traffic mix-the presence of trucks, buses, and other large vehicles can increase risk and have a negative impact on the comfort of
bicyclists.
On-street parking-additional width is needed for bicycle lanes on roads that have on-street parking.
Sight distance-this must be sufficient to allow a motor vehicle operator to either change lane position or slow to the bicyclist's speed when overtaking the bicycle, primarily on rural highways.
Number of intersections-the number and frequency of intersections should be considered when assessing the use of bike lanes. Intersections pose special challenges to bicycle and motor vehicle operators and require special treatments.
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