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Publication Number: FHWA-RD-98-108
Date: February 1998

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:

equation 1 [9]

where:

atsbike= average travel speed of bicycles in km/h;
ltotal= total length of arterial in km over which bicycles travel;
li= length of segment (i) in km; as i= 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 Reportfor 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 HCMfor motor vehicles on arterials.

TABLE 7 Bicycle arterial Level of Service (LOS)

Bicycle running speed 25 km/h
LOS Average travel speed* (km/h)
A ≥ 22
B ≥ 15
C ≥ 11
D ≥ 8
E ≥ 7
F < 7
*computed from Equation [9]; includes stops
SOURCE: Adapted from TRB, 1994.

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