Preparing To Select A Facility Treatment
To determine the appropriate highway design treatment to accommodate bicyclists, several factors associated with the specific route or project must be assessed:
What types of bicyclists is the route most likely to serve?
What type of roadway project is involved (new construction, reconstruction, or retrofit)?
What are the current and anticipated traffic operations and design characteristics of the route that will affect the choice of a bicycle design treatment?
What Types Of Bicyclists Is The Route Most Likely To Serve?
To varying extents, bicycles will be ridden on all highways where they are permitted. All new highways, except those where bicyclists will be legally prohibited, should be designed and constructed under the assumption that they will be used as a bicycle street.
All streets and highways where bicycles are permitted to operate should, at a minimum, incorporate the design treatments recommended in Selecting Roadway Design Treatments to Accommodate Bicyclists (Wilkinson, et. al. 1994) for group A bicyclists (i.e., advanced). Where it is determined that use by group B/C bicyclists (i.e., basic riders and children) is likely, the tables recommending design treatments for group B/C should be used. The group B/C design treatments will also accommodate group A bicyclists.
At a minimum, all streets and highways open to bicycle use should have roadways incorporating the design treatments recommended for group A bicyclists. Where a planning process has determined a given route is the best choice to form part of a network of routes to provide access to the community for group B/C bicyclists, the recommended design treatment appropriate to B/C riders should be implemented.
New Construction And Reconstruction Vs. Retrofitting
The recommended design treatments in the tables (see Wilkinson, et. al. 1994) are most easily implemented when new construction or reconstruction is planned. It is a relatively straightforward process to adopt the specified design treatment for bicycles at the project planning stage.
When implementation involves retrofitting an existing roadway to accommodate bicycle use, the project can be more complex. Existing streets built with a curb and gutter section will often be viewed as having a fixed width and improvements will likely be limited to "moving paint," that is, restriping the existing lanes.
When working with existing streets and highways, planners should investigate the opportunity to make at least minor or marginal improvements. However, where the need is to serve group B/C bicyclists, it is essential to commit the resources necessary to provide facilities that meet the recommended design treatments. Only then can routes and facilities be designated for bicyclists and provide the desired access to the community.
Which Traffic Operations And Design Factors Help Determine The Appropriate Design Treatment?
A general consensus has emerged among transportation planners and engineers working with bicycle facilities on the traffic operations and design factors having the greatest effect on bicycle use. Six factors are most often cited.
Each of these factors is discussed below along with the ranges of values used to differentiate levels of needs. These ranges should only be considered as a general guide; there is little research available, and there is tremendous regional variation in prevailing conditions. For more information, consult Wilkinson, et. al. (1994), especially the six tables where all the factors (except intersections) are incorporated into the design guidelines.
The six major factors are as follows:
Traffic volume. Higher motor vehicle traffic volumes represent greater potential risk for bicyclists and the more frequent overtaking situations are less comfortable for group B/C bicyclists unless special design treatments are provided. The recommendations for bicycle facilities are based on the three ranges of AADT (Average Annual Daily Traffic count):
Low: Under 2,000 AADT
Medium: 2,000 to 10,000 AADT
High: Over 10,000 AADT
Average motor vehicle operating speed. The average operating speed is more important than the posted speed limit, and better reflects local conditions. Higher speeds have a more negative impact on perceived risk and comfort. Four ranges of average speeds are used:
Less than 30 mi/h (less than 48.3 km/h)
30 to 40 mi/h (48.3 to 64.4 km/h)
41 to 50 mi/h (66 to 80.5 km/h)
Over 50 mi/h (over 80.5 km/h)
Traffic mix. The regular presence of trucks, buses, and/or recreation vehicles (i.e., approximately 30 per hour or more) can increase risk and have a negative impact on comfort for bicyclists. At high speeds, the wind blast from such vehicles can create a serious risk of falls. Even at lower operating speeds, shared lane use is less compatible. All types of bicyclists prefer extra roadway width to accommodate greater separation from such vehicles. Many bicyclists will choose a different route or not ride at all where there is a regular presence of such traffic unless they are able to remove themselves several feet from these motor vehicles.
On-street parking. The presence of on-street parking increases the width needed in the adjacent travel lane or bike lane to accommodate bicycles. On street parking also adds the additional element of risk with car doors suddenly opening as bicyclists ride by. Along designated bicycle routes, parking should be off street, or limited in duration.
Sight distance. "Inadequate sight distance" relates to situations where bicycles are being overtaken by motor vehicles and where the sight distance is likely less than that needed for a motor vehicle operator to either change lane positions or slow to the bicyclist's speed. This problem is primarily associated with rural highways, although some urban streets have sight distance problems due to poor design and/or sight obstructions.
The most effective response to the problem is to correct it. Providing for bicycle operation to the right of the designated motor vehicle lane (i.e., on a bike lane or shoulder) or, at speeds less than 41 mi/h (66 km/h), by adding extra width to a wide outside lane, are viable options.
Number of intersections. Intersections pose special challenges to bicycle and motor vehicle operators, especially when bike lanes or separate bike paths are introduced. The AASHTO Guide and various State design manuals include general guidelines for intersection treatments.
While not usually included as a selection factor for bicycle route designation, the number and/or frequency of intersections should be considered when assessing the use of bike lanes. There is some evidence to suggest that the disruption in traffic operations associated with bike lanes is temporary. Over time, both bicyclists and motorists adapt to the new traffic patterns, learning to look for each other and effect merges prior to intersections.
Beginning Now To Develop Bicycle And Pedestrian Friendly Communities
There are a number of specific steps that communities can take to put them on the road to being known as bicycle and pedestrian friendly. The Capital District Transportation Committee (CDTA) has developed the following list of actions organized under five main headings, ranging from immediate and low-cost steps, to long term projects involving significant investment (CDTA 1994).
1. Immediate Steps to Improve Existing Bicycle/Pedestrian Facilities
a. Clear roadway shoulders of glass and other sharp objects that could puncture bicycle tires or cause injury to pedestrians.
b. Keep roadway shoulders clear of seasonal hazards such as snow, ice, raked leaves, tree limbs, etc.
c. Devote greater attention to repairing pot holes. These holes are even more detrimental to bicycles than to autos.
d. Maintain existing striping on roads; clearly distinguish between road shoulder and auto lane.
e. Repave road shoulders as roads are repaved; paved shoulders are safer and more pleasant to walk and ride upon.
f. Add informational signs to heighten awareness of other transportation means: "Bike/Pedestrian Crossing", "Share the Road..", etc.
g. Improve signal timing to allow adequate time for persons to cross road. Devote special attention to areas with children and senior citizens.
h. Repair and maintain existing traffic control devices, especially walk lights.
i. Crosswalk improvements: Repair and maintain vehicular stop lines and crosswalk stripes.
j. Prohibit "right on red" turns in high density pedestrian crossing zones.
2. Low-Cost Steps to Improve Bicycle/Pedestrian Facilities
a. Create advanced "bicycle stop lines" at intersections to increase rider visibility & safety.
b. Create bicycle "safe zones" for non-turning cyclists in areas with vehicular right turn lanes.
c. Remove existing circulation barriers. Repetition poles, signs, etc. off of sidewalks and crosswalks.
d. Replace slotted storm drain grates with safer, non tire-eating storm drain grates.
e. Crosswalk improvements: Install distinctive road textures/paving in crosswalks and include highly visible striping.
f. Create textured and striped pedestrian islands in wide roadways as pedestrian-safe zones.
3. Moderate-Cost Steps to Improve Bicycle/Pedestrian Facilities
a. Improve existing roadway shoulders during general maintenance, scheduled improvements and new construction to accommodate cyclists & pedestrians.
b. Level-off storm drains. Much safer for ALL - pedestrians, cyclists, autos and transit.
c. Provide bike racks and benches at major population, employment, and shopping centers.
d. Crosswalk improvements: Install traffic control devices - walk/don't walk lights, etc.
4. New Bicycle/Pedestrian Facility Construction
a. Construct bike lanes to appropriate specifications and include adequate signage and directional striping.
b. Construct bike lanes and paths with "continuity & linkages" in mind. Build new sidewalks and bikeways to connect to existing pathways.
c. Actively preserve available "rights of way" for future construction of bike and recreational paths.
d. Enhance bicycle/pedestrian linkages from residential areas to employment centers and shopping centers through the additional construction of sidewalks and bikeways.
e. Build additional sidewalks and bikeways with particular attention to transit boarding zones and areas with high levels of bicycle/pedestrian activity (schools, libraries, playgrounds, backfields, shopping areas, etc.).
f. Reinforce natural pedestrian thoroughfares when constructing new walkways. Footpaths generally show the most direct route between two points.
g. Improve street lighting to enhance bicycle/pedestrian safety and security.
h. Install bicycle lockers or "bicycle safes" at highly-used bicycle activity areas.
i. Develop bicycle parking facilities in existing automobile garages.
j. Develop landscaping designs with attention to safety and security as well as aesthetics.
k. Incorporate facilities to safely accommodate pedestrians and bicycles on existing automobile bridges.
l. Construct separate pedestrian/bicycle bridges and tunnels where no safe alternative exists.
5. Planning Future Investments in Bicycle/Pedestrian Facilities
a. Identify specific routes to link existing pedestrian and bicycle-generating activity centers via sidewalks, bicycle paths and bicycle lanes; develop these routes as part of an ongoing capital Improvement process.
b. Develop a community-wide Pedestrian and Bikeway Plan to integrate and enhance non-motorized access to future activity centers.
c. Plan for the construction sidewalks and bikeways to enhance access to general points of interest such as the schools, parks, museums, business districts, hiking trail heads, etc.
d. Adopt performance standards, including a policy for maintenance responsibilities, requiring the installation of sidewalks based upon street classification and intensity of development.
e. Require that pedestrian/bicycle circulation considerations be part of any road widening improvements.
f. Allow for the flexible placement of sidewalks and bikeways to preserve topographic or natural features.
g. Promote the inclusion of bicycle parking facilities in the design of new automobile parking facilities.
h. Design new residential subdivisions that effectively incorporate adequate pedestrian and bicycle access to major business, retail and activity centers.