Guide for the Development of Bicycle Facilities

Excerpts from the 1999 AASHTO

The AASHTO guide is the industry standard for bicycle facility design issues. Subjects include shared roadways, signed shared roadways, bike lanes, shared use paths (trails), bicycle planning, and other issues. Below are some notable excerpts.

LIB recommends that every town and county in Illinois get a copy. Bicyclists, encourage your local agencies to purchase and use the AASHTO guide for roadwork and other projects that affect cycling. Go to the AASHTO website for ordering information.

Design Highways for Bicyclists

Assume cyclists will use the roads: "All highways, except those where cyclists are legally prohibited, should be designed and constructed under the assumption that they will be used by cyclists. Therefore, bicycles should be considered in all phases of transportation planning, new roadway design, roadway reconstruction, and capacity improvement and transit projects." Page 1

Measuring Bicycle Demand

Bicycle counts and potential demand: "Bicycle counts can be used to identify locations of high use. However, caution should be exercised when using bicycle counts as a measure of current demand. These numbers can considerably underestimate potential users. Traffic generators along the prospective route should be evaluated as to the potential bicycle traffic they would generate, given better conditions for bicycling."Page 9

Consider Different Cyclist Types

Bicycle facilities for different cyclist types: "...The choice of highway design will affect the level of use, the types of user that can be expected to use any given road, and the level of access and mobility that is afforded bicyclists. For example, a four-lane divided highway with 3.6-m (12-foot) travel lanes, no shoulder and an 85 km/hr (55 mph) speed limit will attract only the most confident of riders. The same road with a 1.5-m (5-foot) shoulder or bike lane might provide sufficient "comfortable operating space" for many more adult riders, but would still not be comfortable for children or less confident adults. This latter group might only be accommodated through an alternative route using neighborhood streets linked by short sections of shared use path. If such an alternative route is provided and the four-lane road has a continuous paved shoulder, most experienced and many casual adult riders will continue to use the shoulder for the sake of speed and convenience."Pages 6-7

Space Recomendations for Bicyclists

Minimum bicycle facility width: "An operating space of 1.2 m (4 feet) is assumed as the minimum width for any facility designed for exclusive or preferential use by bicyclists. Where motor vehicle traffic volumes, motor vehicle or bicyclist speed, and the mix of truck and bus traffic increase, a more comfortable operating space of 1.5 m (5 feet) or more is desirable." Page 5

Paved shoulder minimum width: "Paved shoulders should be at least 1.2 m (4 feet) wide to accommodate bicycle travel.... Additional shoulder width is also desirable if motor vehicle speeds exceed 80 km/h (50 mph)...." Page 16

Minimum width of bike lanes, no curb and gutter: "For roadways with no curb and gutter, the minimum width of a bike lane should be 1.2 m (4 feet).... A width of 1.5 m (5 feet) or greater is preferable and additional widths are desirable where substantial truck traffic is present, or where motor vehicle speeds exceed 80 km/h (50 mph)." Pages 22-3

Minimum width of bike lanes, with curb and gutter: "(For a) bike lane along the outer portion of an urban curbed street where parking is prohibited, the recommended width of a bike lane is 1.5 m (5 feet) from the face of a curb or guardrail to the bike lane stripe. This 1.5-m (5-foot) width should be sufficient in cases where a 0.3-0.6 m (1-2 foot) wide concrete gutter pan exists...." Page 23

Bike lane/shoulder maintenance and cleaning: "Regular maintenance of bicycle lanes (and shoulders) should be a top priority, since bicyclists are unable to use a lane with potholes, debris or broken glass." Page 8

Wide curb lanes: "Wide curb lanes for bicycle use are usually preferred where shoulders are not provided, such as in restrictive urban areas. On highway sections without designated bikeways, an outside or curb lane wider than 3.6 m (12 feet) can better accommodate both bicycles and motor vehicles in the same lane and thus is beneficial to both .... In general, 4.2 m (14 feet) of usable lane width is the recommended width for shared use in a wide curb lane." Page 17

Sidewalks and Bicyclists

Sidewalks as bike facilities: "In general, the designated use of sidewalks (as a signed shared facility) for bicycle travel is unsatisfactory. It is important to recognize that the development of extremely wide sidewalks does not necessarily add to the safety of sidewalk bicycle travel.... Sidewalk bikeways should be considered only under certain limited circumstances, such as: a) To provide bikeway continuity along high speed or heavily traveled roadways having inadequate space for bicyclists, and uninterrupted by driveways and intersections for long distances. b) On long, narrow bridges...." Page 20

"Utilizing or providing a sidewalk as a shared use path is unsatisfactory for a variety of reasons. Sidewalks are typically designed for pedestrian speeds and maneuverability and are not safe for higher speed bicycle use. (Various bicycle/sidewalk user conflicts described)...At intersections, motorists are often not looking for bicyclists (who are traveling at higher speeds than pedestrians) entering the crosswalk area, particularly when motorists are making a turn. Sight distance is often impaired...." Page 58

"It is important to recognize that the development of extremely wide sidewalks does not necessarily add to the safety of sidewalk bicycle travel. Wide sidewalks might encourage higher speed bicycle use and can increase potential for conflicts with motor vehicles at intersections, as well as with pedestrians and fixed objects." Page 58

Shared Use Paths and Bicyclists

Adjacent path crossings: "...occur where a path crosses a roadway at an existing intersection between two roadways.... It is preferable that this type of crossing be carefully integrated close to the intersection so as to allow motorists and path users alike to recognize each other as intersecting traffic." Page 48

Shared use paths and on-road facilities: "Shared use paths should not be used to preclude on-road bicycle facilities, but rather to supplement a system of on-road bike lanes, wide outside lanes, paved shoulders and bike routes." Page 33

"When two-way shared use paths are located immediately adjacent to a roadway, some operational problems are likely to occur. (9 listed) ...other types of bikeways are likely to be better suited to accommodate bicycle traffic along highway corridors, depending upon traffic conditions. Shared use paths should not be considered a substitute for street improvements even when the path is located adjacent to the highway, because many bicyclists will find it less convenient to ride on these paths compared with the streets, particularly for utility trips." Page 35

Width of shared use paths: "Under most conditions, a recommended paved width for a two-directional shared use path is 3.0 m (10 feet)." Page 35

Intersections of roads and shared use paths: "For a roadway user (at a path crossing), a clear message must be presented in a location where it will be seen by that user. Traditional treatments have included (various signs), or flashing yellow lights at the crosswalk. However, signs are frequently placed at the side of the road, out of motorists' line of sight, and historically, flashing yellow lights have also been used at non-crosswalk applications. In recent years, new applications have been developed, including...'zebra-style' or colorized pavement crosswalks, which are far more visible than traditional designs...." Page 53

"Traffic signals for path-roadway intersections are appropriate under certain circumstances. The MUTCD2 lists 11 warrants for traffic signals, and although path crossings are not addressed, bicycle traffic on the path may be functionally classified as vehicular traffic and the warrants applied accordingly." Page 50