A bicycle can be ridden on almost any kind of roadway, yet certain traffic conditions create a sense of discomfort, even for the skilled bicyclist. A high volume of traffic is one of those conditions and can inhibit a bicyclist’s feeling of safety and comfort. This is particularly true when no bicycle facilities exist on these roadways.
Motor vehicle traffic speed is equally critical to bike-ability and safety. Though bicyclists may feel comfortable on streets that carry a significant amount of traffic at low speeds, faster speeds increase the likelihood of bicyclists being struck and seriously injured. At higher speeds, motorists are less likely to stop in time to avoid a crash. At a mere 49.9 km/h (31 mi/h), a driver will need about 61.0 m (200 ft) to stop, which may exceed available sight distance. Reducing speed limits and subsequent motor vehicle speeds should improve bicycle safety. A driver traveling at 30.6 km/h (19 mi/h) can stop in
about 30.5 m (100 ft).
High motor vehicle traffic volume can create a sense of discomfort for bicyclists when they don’t have space.
Unfortunately, many of our streets are designed to accommodate higher motor vehicle traffic volumes and speeds in an attempt to better handle peak hour congestion. Most bicyclists will try to avoid these streets if possible, but a problem exists if these same streets are part of a bicycling corridor. Fortunately, there are tools that can improve the speed profile, primarily by redesigning streets through traffic calming measures. However, care must be taken to ensure that the traffic calming method is suitable for bicycling. New streets can also be configured with lower design speeds without a great sacrifice in capacity. Speed reductions can increase bicycling safety considerably. The safety benefits of reduced speeds extend to motorists and pedestrians as well. On slow speed city streets and lightly traveled roadways, bicyclists may safely operate in the normal traffic lanes. However, on heavily traveled streets, bicyclists need space to operate and to provide room for overtaking motorists. Space can be provided through the use of bike lanes, paved shoulders, or wide curb lanes (although wide curb lanes may not be the best choice for a high-speed and high-volume combination), and these facilities can often be created through the narrowing of traffic lanes through remarking, or what has come to be known as “road diets” (e.g., reducing traffic lanes from 3.7 m (12 ft) to 3 or 3.4 m (10 or 11 ft).