Click for next page ( 110

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 109
J-1 APPENDIX J PRIMER ON DESIGNING BICYCLE FACILITIES When considering, planning, or constructing a bike facility, the 15 feet (4.5 m): preferred where extra space required for maneu- first step is to identify the project scope. As more detailed information vering (e.g., on steep grades) or to keep clear of on-street parking becomes available on site limitations, construction cost, and funding or other obstacles project impacts, the scope will be refined through the design develop- ment process. Basic considerations in defining the scope are facility Continuous stretches of lane 15 feet (4.5 m) or wider may encour- type (on-street, off-street, equipment), paving, drainage, structures, age the undesirable operation of two motor vehicles in one lane. Where and design guidelines used to identify dimensions such as width of this much width is available, it is recommended to more seriously paths. The following text provides some basics in identifying the consider striping bike lanes or shoulders. project scope. When developing the cost of on-street bicycle facilities and shared use paths, the user will need to know how to select construction Bicycle Lanes materials, recommend dimensions, and decide on a path surface. The following is a primer for design consideration of bicycle facilities. Critical dimensions Pavement design focuses primarily on shared use paths and other Bicycle lane width off-street facilities. Bicycle facilities on roadways are considered to 4 feet (1.2 m): minimum width of bike lane on roadways with no be a minor part of the structural design of the roadway and are there- curb and gutter fore not included as part of the primer. This primer should be used 5 feet (1.5 m): minimum width of bike lane when adjacent to in conjunction with the 1999 AASHTO Guide for the Development parking, from the face of the curb or guardrail of Bicycle Facilities. 11 feet (3.3 m): shared bike lane and parking area, no curb face 12 feet (3.6 m): shared bike lane and parking area with a curb face On-Street Facility Bicycle lane stripe width On-street facilities consist primarily of paved shoulders, wide 6-inch (150 mm): solid white line separating bike lane from curb lanes, and bike lanes. All are part of the roadway surface that motor vehicle lane (maybe raised to 8-inches (200 mm) for is also used by motor vehicles. Structural requirements of the road emphasis) bed including pavement depth are dictated by motor vehicles: 4-inch (100 mm): optional solid white line separating the bike lane from parking spaces Paved Shoulders Off-Street Facility (typically shared use paths) Critical dimensions Less than 4 feet (1.2 m): any additional width of paved shoulder Standards recommend the width be 10 feet or 3 meters for a is preferred than no facility at all, but below 4 feet a shoulder two-way, shared use path on a separate right of way. Other critical should not be designated or marked as a bicycle facility measurements include the following: 4 feet (1.2 m): minimum width to accommodate bicycle travel measurement must be of useable width and should NOT include the gutter pan or any area treated with rumble strips 8 feet (2.4 m) may be used where bicycle traffic is expected to 5 feet (1.5 m) or more: minimum width recommended from the be low at all times, pedestrian use is only occasional, sightlines face of a guardrail, curb or other barrier are good, passing opportunities are provided, and maintenance vehicles will not destroy the edge of the trail Widths should be increased with higher bicycle use, motor vehi- 12 feet is recommended where substantial use by bicycles, cle speeds above 50 mi/hr, and higher percentage of truck and bus joggers, skaters, and pedestrians is expected, and where grades traffic. are steep 2 feet of graded area should be maintained adjacent to both sides of the path Wide Outside Lanes 3 feet of clear distance should be maintained between the edge of the trail and trees, poles, walls, fences, guardrails or other lateral Critical dimensions obstructions 14 feet (4.2 m): recommended width for wide outside lane width 8 feet of vertical clearance to obstructions should be maintained; must be useable and measurement should be from the edge line rising to 10 feet in tunnels and where maintenance and emergency or joint of the gutter pan to the lane line vehicles must operate

OCR for page 109
J-2 Drainage Preserve natural ground cover adjacent to the trail to inhibit erosion The AASHTO Guide recommends a cross slope of 2%. The fol- Include price of seeding, mulching, and sodding of slopes, lowing are considerations to ensure adequate drainage: swales, and other erodible areas in the cost Slope the trail in one direction rather than having a crown in the middle of the trail Proper drainage is one of the most important factors affecting pave- Provide a smooth surface to prevent ponding and ice formation ment performance. Proper drainage entails efficient removal of excess Place a ditch on the upside of a trail constructed on the side of water from the trail. Surface water runoff should be handled using a hill swales, ditches, and sheet flow. Catch basins, drain inlets, culverts and Place drainage grates, utility covers, etc., out of the travel path underground piping may also be necessary. These structures should of bicyclists be located off the pavement structure.