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The central findings of this study have important implications for trail design. The following is a list of key findings that can be used to inform design choices:
The findings of this study provide strong support for the standard trail width guidance provided in the AASHTO Guide for the Development of Bicycle Facilities .(2) Trails having 2.4-m (8.0-ft) width, which AASHTO recommends only in "rare instances," were found to have poor LOS, except at very low volumes or with user mixes that included few pedestrians and runners. The findings of this research support AASHTO's minimum "recommended paved width for a two-directional shared-use path of [3.0 m] ten feet." [8]
The study found that widths of 3.4–4.6 m (11.0–15.0 ft) provide improved LOS for higher volumes and more balanced user mixes than narrower widths. This is consistent with AASHTO recommendations that "under certain conditions it may be necessary or desirable to increase the width of a shared-use path to 3.8 m (12.0 ft) or even to 4.3 m (14.0 ft), due to substantial use by bicycles, joggers, skaters and pedestrians, ...." [9] Trails of 3.4–4.6 m (11.0–15.0 ft) are wide enough to operate as three-lane paths. The increased passing capacity provided by a trail that operates as three lanes improves LOS and increases the trail's ability to absorb higher volumes and more diverse mode splits without severely degrading service.
A striped centerline was found to have strong impact on the bicyclist's perception of freedom to maneuver. This finding appears to support the intent of trail designers in providing a centerline, which is clear delineation of opposing travel lanes. A centerline reinforces the idea that, to pass a slower-moving user, the cyclist may need to use the travel lane of opposing trail users and should pass only when the opposing lane is open.
This research found that the presence of a centerline stripe results in a significant reduction in the LOS. It appears that bicyclists may feel less comfortable making a same-direction passing movement when a centerline stripe is present. While this finding might appear initially to mean that a centerline stripe degrades pathway LOS and should not be used, it is important to note that there may be other valid safety reasons for providing a centerline stripe, particularly on crowded trails, on curves with limited sight distance, and in other appropriate circumstances.
Only two trails in this study were striped with more than two travel lanes. The Pinellas Trail was striped as a three-lane trail, with one lane in each direction for bicycles and skaters and one lane for pedestrians. The Lakefront Trail was striped as four lanes, with two lanes in each direction. These two examples did not represent a sufficient number of study trails to fully assess the impact of multilane striping patterns on LOS. However, it is likely that having sufficient trail width for a four-lane operation (a minimum of 4.6 m (15.0 ft)) increases the ability of bicyclists to pass slower-moving users without encountering blockage from trail users in the opposing lanes.
A number of shared-use trails have been designed with two treadways in the same trail corridor. Often, one is paved and the other is a soft surface. Frequently, one of the treadways is provided for exclusive use by one or two trail user groups, or user restrictions are imposed on both paths in an effort to segregate users.
Given this study's findings about the impact of user mix on bicyclist LOS, a multiple treadway design that effectively reduces the number of pedestrians and runners mixing with bicyclists will have significant LOS benefits for the treadway used by bicyclists. This study did not address compliance with use restrictions, an issue that is often raised by trail managers as a problem when separate treadways are provided.
While this study did not examine issues related to trail operations and management, the framework of the tool may lend itself to applications in this area. Such possibilities might include the use of LOS grades in warrants for trail etiquette or warning signs. Trail etiquette signs address the sharing of treadways or the use of designated passing protocols. LOS may also be useful in setting trail speed limits or other advisory or regulatory protocols that will increase user safety and moderate user conflicts.
HRT-05-138 |
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