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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
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Publication Number: FHWA-HRT-05-138
Date: July 2006
Shared-Use Path Level of Service Calculator
A User's Guide
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3. LOS FOR SHARED–USE PATHS
WHAT IS LOS?
For motor vehicles on roadways, HCM defines LOS as a "quality measure describing operational conditions within a traffic stream, generally in terms of such service measures as speed and travel time, freedom to maneuver, traffic interruptions, and comfort and convenience."(3) HCM defines six levels of service for a particular facility type and uses letters A to F to represent them, from best to worst. Each LOS represents a range of operating conditions. Safety is not explicitly included in the measures that establish motor vehicle LOS.
The trail LOS model developed through this research is similar to that which is used for motor vehicle LOS. Listed below are some key similarities and differences.
The key difference is:
It is important to note a host of other factors the reader may want to consider in a trail users' assessment of comfort and enjoyment of a trail, such as the following:
Just as motor vehicle LOS measures a limited aspect of the experience of driving and does not take into account the quality of the vehicle in which a person travels, the scenery along the road, etc., the trail LOS model has similar limitations. While such factors of trail design are important to the user's experience, they will be left to further research.
THE SHARED–USE PATH LOS MODEL
The Shared–Use Path LOS (SUPLOS) model is a mathematical formula that uses select inputs describing conditions along a trail to calculate an LOS score. A key task in model development was to determine what inputs should be used and what mathematical relationships existed among them. The goal was to develop a formula that would yield scores consistent with the evaluation of similar conditions made by participants in the perception survey. A secondary objective was to use only those inputs that are truly necessary and most readily available.
Using a variety of statistical methods, the operational and user perception survey variables were examined to evaluate which variables had the most influence in determining the grades users gave to the different conditions represented in the video clips. A model (mathematical equation) was built that would use the most significant factors as inputs to generate LOS scores and grades. The model was tested and adjusted to ensure that it generated grades that closely correlated to the perception scores that trail users gave each video clip.
The equation in figure 1, below, is the basic SUPLOS model. Appendix B provides additional details about the factors used in the model. For a complete explanation of the derivation of the model see chapter 7 of the Final Report.(8)
Figure 1. Equation. Basic SUPLOS model.
E = Events = Meetings per minute + 10 (active passes per minute)
The SUPLOS model generates a LOS score between zero and five. Table 5 describes the SUPLOS scale, which shows how raw scores correspond to letter grades. An A is the highest score, excellent, and an F is the lowest score.
Table 5. SUPLOS scale.
INTERPRETING SHARED–USE PATH LOS GRADES
In general, grades A–C can be considered acceptable levels of service and D–F can be considered degraded levels of service. The LOS descriptions in table 6 provide a more refined framework.
A benefit of this LOS model is that it provides a uniform quantitative measurement for use throughout the United States and North America. However, each political jurisdiction and trail managing agency certainly has latitude to adopt different policies covering acceptable levels of service for trails within their own communities, as is the case with roadway levels of service. To some degree, determining what scores and grades are acceptable can vary for each different application of the model. For example, a jurisdiction may elect to establish a policy to ensure that new trails meet a higher performance standard than the standard considered acceptable for existing trails.
Table 6. Interpreting SUPLOS grades.
A: Excellent. Trail has optimum conditions for individual bicyclists and retains ample space to absorb more users of all modes, while providing a high–quality user experience. Some newly built trails will provide grade–A service until they have been discovered or until their ridership builds up to projected levels.
B: Good. Trail has good bicycling conditions, and retains significant room to absorb more users, while maintaining an ability to provide a high–quality user experience.
C: Fair. Trail has at least minimum width to meet current demand and to provide basic service to bicyclists. A modest level of additional capacity is available for bicyclists and skaters; however more pedestrians, runners, or other slow–moving users will begin to diminish LOS for bicyclists.
D: Poor. Trail is nearing its functional capacity given its width, volume, and mode split. Peak–period travel speeds are likely to be reduced by levels of crowding. The addition of more users of any mode will result in significant service degradation. Some bicyclists and skaters are likely to adjust their experience expectations or to avoid peak–period use.
E: Very Poor. Given trail width, volume, and user mix, the trail has reached its functional capacity. Peak–period travel speeds are likely to be reduced by levels of crowding. The trail may enjoy strong community support because of its high usage rate; however, many bicyclists and skaters are likely to adjust their experience expectations, or to avoid peak–period use.
F: Failing. Trail significantly diminishes the experience for at least one, and most likely for all user groups. It does not effectively serve most bicyclists; significant user conflicts should be expected.
LOS SCORES FOR 15 STUDY TRAILS
Table 7 provides LOS scores and grades for 15 trails studied as part of this research. This table includes two–way and one–way user volumes, mode splits, trail widths, and presence of centerline variables. It also provides a data profile for the average trail and its corresponding LOS score and grade (3.15, C).
Table 7. Study trail level of service grades and characteristics.
† The profile of the Average Trail was created by averaging the data for 13 of the 15 study trails. The high and low volume trails (W&OD and Lakefront) were dropped from the mix and the data of the remaining trails was averaged. The mode splits were rounded to the nearest increment of five.