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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
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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.
