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Capacity
Analysis of Pedestrian and Bicycle Facilities:
Recommended Procedures for the "Bicycles" Chapter of the Highway Capacity Manual |
4
- COMBINED BICYCLE FACILITIES
This
section focuses on operational analyses of combined designated
on-street bicycle facilities with uninterrupted and interrupted
elements (e.g., arterials).
The research
team proposes to use average bicycle travel speed, including
stops, as the service measure of effectiveness for combined
bicycle facilities. The average travel speed is based simply
on the travel distance between two points and the average
amount of time required to traverse that distance, including
stops at intersections.
For these procedures,
combined bicycle facilities are on-street arterials made up of both
segments and intersections with designated bicycle facilities. The first
step in analyzing an arterial is to define its limits. Once the limits
are defined, the arterial must be broken into individual segments and
intersections for analysis. Average travel speed is then computed as
follows:
ltotal = total length of arterial in km over which bicycles travel; li = length of segment (i) in km; asi = bicycle running speed over segment (i) in km/h; and d j = average bicycle delay at intersection (j) in s. Similar to motor vehicle traffic, bicycle speeds on uninterrupted facilities are not affected by volume over a large initial range. It is recommended that 25 km/h (15.5 mi/h) be used as the average bicycle running speed for the combined bicycle facility procedure. This speed falls within the range of speeds from previous studies as reported in the Bicycle Literature Review Section of the Research Report for this project ( Rouphail et al., 1997 ). The research team acknowledges that there are many other possible factors affecting speed, including adjacent motor vehicle traffic, which is often moving much faster than the bicycles; commercial and residential driveways; adjacent on-street parking; lateral obstructions; extended sections with appreciable grades; and other local factors. Unfortunately, factors such as these have not been sufficiently researched to date to make any quantitative assessment of their effects. Intersection delay is computed as described in the Interrupted Facilities section. It is then recommended that the LOS be determined as shown in Table 7. This table is based on roughly the same ratios of average travel speeds to the ideal average speed currently given in Chapter 11 of the HCM for motor vehicles on arterials. | |||
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