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Evaluating and Refining the Bicycle Level of Traffic Stress (BLTS) Methodology for Geometric Design of Intersections

Description:

Performance-based practical design calls for the scope of a project to remain within the intended purpose and need. In considering the geometric design of intersections, those needs are often defined by the design vehicle. Some intersections are specifically designed to handle heavy vehicles progressing along a truck route while the design vehicle for a minor neighborhood intersection may be much smaller. In the same manner, bicycle level of traffic stress (BLTS) allows for the classification of a design bicycle user. BLTS is a measure used to map the level of traffic stress accepted by four different types of bicycle users: children (LTS1), “interested but concerned” adults (LTS2), “enthused and confident” adults (LTS3), and “strong and fearless” adults willing to accept larger speed differentials (LTS4). Mekuria et al showed that at the segment level, the geometric needs (e.g., cross-sectional elements) vary with each user type. This research would evaluate and extend the current methodology for segments to intersections.

Objective:

The objective of this research is to improve the riding experience for bicyclists through the development of practitioner guidance regarding the multimodal intersection operations and geometric design elements that impact bicyclists at intersections. Understanding that there are many geometric elements within an intersection, this project would first identify and then prioritize each element on the basis of impact to bicyclists’ stress level and feasibility of collecting data. For the highest priority elements, the research team would then collect data in an effort to determine the needs of each user type with regard to those elements. The test subjects should represent all user types and ages. The data would then inform the categorization of elements – either the presence or absence of an element or the quantitative value (e.g. facility width) – for each of the four user types.

Research products include:

  1. Prioritized list of geometric elements, including recommendations of those elements that have a substantial impact on bicyclist stress level and require further research but which were not prioritized in this project;

  2. Geometric element – user type matrix listing the criteria of each element studied to meet the needs of every user type;

  3. Identification of each section of the Guide for the Development of Bicycle Facilities which is impacted by the research; and,

  4. Design guidance for each of the sections identified in Product 3 for possible inclusion in the next edition.

Benefits:

By clearly defining the geometric needs of each of the four user types, professionals will be empowered to design the intersection for a specific user type. Further, the research will provide national guidance, which can be referenced in justifying why an element was included or excluded, widened, or narrowed.

Related Research:

Mekuria et al.1 classified the four levels of traffic stress based on the four types of cyclists outlined by Geller2. Mekuria et al. developed a framework for determining geometric needs for each of the cyclist types on segments, but no such work exists at intersections. Most research regarding bicyclists at intersections has focused on technological or pavement marking implements to improve bicyclist safety3,4,5. Current efforts are underway to address the safety of bicycles at intersections6, but this effort, along with existing guidance documents7,8, does not consider the differences in needs among the four cyclist types. Current efforts also exist to understand bicyclist facility preferences by cyclist type, but the scope with regards to intersections is limited to traffic control. Further, the resulting guidance will focus on planning level decisions9.

1Mekuria, Mazza C., Peter G. Furth, and Hilary Nixon. "Low-stress bicycling and network connectivity." (2012).

2Geller, Roger. Four Types of Cyclists. Portland, OR: City of Portland Office of Transportation, undated, circa 2007,

http://www.portlandonline.com/transportation/index.cfm?&a=237507&c=44597

(accessed August 5, 2016).

3Paulsen, Kirk, et al. "Analysis of Active Warning Sign to Address Potential Bicycle 'Right-Hook' Conflict at Signalized Intersections." Transportation Research Board 95th Annual Meeting. No. 16-4330. 2016.

4Kading, Andrew. "Performance Implications of Bicycle Specific Treatments at Signalized Intersections." (2016).

5Gilpin, Joe. "Building Better Communities Through Complete Streets-The Protected Intersection." Institute of Transportation Engineers. ITE Journal86.3 (2016): 40.

6NCHRP 15-63: Guidance to Improve Pedestrian and Bicycle Safety at Intersections. Research in Progress.

http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=4048.

7Bowling, R. G., et al. Multimodal Level of Service Analysis for Urban Streets, NCHRP Report 616. Transportation Research Board, Washington, DC (2008).

8Highway Capacity Manual 2010. Transportation Research Board, National Research Council. Washington, DC (2009).

9NCHRP 08-102: Bicyclist Facility Preferences and Effects on Increasing Bicycle Trips. Research in Progress.

http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=3861.

Implementation:

The resulting product will be used by traffic engineers and geometric designers. It will detail the design elements which are desired by each of the four user types. With an understanding of the expected bicycle user base, the BLTS methodology will assist and provide the operational tools for planners and engineers in identifying the geometric elements which are conducive to those users. Further, it will provide a scientific basis for designers to justify the inclusion or exclusion of various roadway elements.

Target Audience: Traffic and geometric design professionals

Key Decision Makers: State DOT Chief Engineers

AASHTO Committees: Technical Committee on Geometric Design; Joint Technical Committee on Non-Motorized Transportation

Early Adopters: FHWA Non-Motorized Transportation Pilot Program Communities (Columbia, MO; Marin County, CA; Minneapolis, MN; and Sheboygan County, WI)

Relevance:

Currently, there is no national work recognizing and classifying the unique bicycle user types leading to the inability to identify a “design user”. Without this context, there is no standard and consistent method to determine what geometric elements are appropriate at an intersection. Instead, designers are left to either assume all intersections with a given bicycle volume should have similar elements or guess at the appropriate elements for the most populous user type. The narrow scope required for performance based practical design is undefinable because the user’s needs are unknown. This can lead to either under- or over-designing the intersection for bicyclists.

Sponsoring Committee:AFB10, Geometric Design
Research Period:24 - 36 months
Research Priority:Medium
RNS Developer:Shannon Warchol, Henry Brown, Hermanus Steyn, Nick Foster, Matt Braughton, Karla Kingsley, Sarah O'Brien
Source Info:Developed as part of the 2016 mid-year meeting of the TRB Committee on Geometric Design (AFB10), TRB Committee on Operational Effects of Geometrics (AHB65), and AASHTO Technical Committee on Geometric Design.
Date Posted:10/26/2016
Date Modified:11/14/2016
Index Terms:Intersections, Geometric design, Highway design, Cyclists, Stress (Psychology), Neighborhoods,
Cosponsoring Committees:AHB65, Operational Effects of Geometrics
 
Subjects    
Highways
Pedestrians and Bicyclists
Design
Operations and Traffic Management
Safety and Human Factors

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