The National Academies

NCHRP 15-66 [Active]

Operational Performance and Safety Effects of Arterial Weaving Sections

  Project Data
Funds: $750,000
Staff Responsibility: David M. Jared
Research Agency: University of Florida
Principal Investigator: Lily Elefteriadou
Effective Date: 11/16/2020
Completion Date: 5/16/2023



Arterial roadways are crucial links in the national transportation system. Providing both local and regional mobility and access, they are critical to economic vitality and quality of life in the United States. As drivers place increasing demands on transportation infrastructure and freeway congestion continues to increase, arterials have become an alternative route for many drivers, resulting in the lower performance of these roadways.


In many areas, weaving maneuvers negatively affect arterial operations and safety. For this research, arterial weaving is defined as the crossing of two or more traffic streams in the same direction between two or more access points on a multi-lane urban street with some type of traffic control. Furthermore, weaving maneuvers can affect the operations and safety of many alternative intersection configurations, including median U-turns and restricted crossing U-turns.


Understanding the operational and safety performance of arterials and the effects of weaving thereon is important for transportation agencies tasked with maintaining these roadways. The Highway Capacity Manual, Sixth Edition (HCM), provides a methodological approach for estimating the performance of weaving sections on freeway segments. This methodology, however, is not applicable to arterial weaving due to differences between freeways and arterials in traffic control, traffic flow characteristics, and driver behavior.




The primary objective of this research project is to develop a deterministic method for evaluating the operational performance of weaving sections on arterials. The secondary objective is to identify the safety effects of varying geometric, volume, and traffic control conditions in weaving sections on arterials.


Accomplishment of the project objective will require at least the following tasks:




Task descriptions are intended to provide a framework for conducting the research. The NCHRP is seeking the insights of proposers on how best to achieve the research objective. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and contract time. Proposals must present the proposers’ current thinking in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach to meeting the research objective.


Task 1. Synthesize operational analysis methods and performance measures for arterial weaving. Review prior research on arterial weaving operational analysis. Identify safety performance-related research that could apply to arterial weaving. The product of this task shall be a technical memorandum summarizing the synthesis.


Task 2. Develop a list of performance measures for arterial weaving sections. Using the findings from Task 1, identify a potential list of performance measures suitable for arterial weaving sections. The product of this task shall be the list of performance measures presented in a technical memorandum with annotations explaining each measure and the reason for its inclusion in the list. 


Task 3. Propose data collection approaches. Propose multiple approaches to collecting data for evaluation of the performance measures identified in Task 2. Provide descriptions of types and amounts of data that can be collected with each approach. Expected data elements shall include, at minimum (a) vehicle trajectory; (b) origin-destination pattern; (c) site geometry; and (d) speed of weaving and non-weaving vehicles. Field data collection shall be emphasized but may be supplemented with traffic simulation. Existing data sources should also be considered. The material developed in this task shall be included as a chapter in Interim Report 1.  


Task 4. Submit Interim Report 1. Summarize the results of Tasks 1 to 3 and recommend which data collection approach(es) should be used in subsequent tasks. Findings from Interim Report 1 shall be presented at an in-person meeting. NCHRP approval of Interim Report 1 is required before work on Task 5 may begin.  


Task 5. Develop a data collection plan. Following NCHRP approval of Interim Report 1, prepare and submit a technical memorandum containing a data collection plan based on the collection approach(es) recommended in Task 3 and approved in Task 4. Specify study sites and describe the characteristics thereof, including but not limited to, geographic, geometric, volume, and traffic conditions. NCHRP must approve the data collection plan before work on Task 6 may begin.


Task 6. Implement data collection. Collect data at sites approved in Task 5. Notify NCHRP of any changes to the data collection plan, e.g., additional and/or substitute performance measures utilized during data collection. The first product of this task shall be a technical memorandum including (a) summaries of the physical, operational, and safety data collected per site; and (b) evaluation of the scope of the data set, e.g., justification of additional sources.


NCHRP approval of the memorandum is required before Task 7 work begins. The second product shall be an annotated database that includes (a) data elements collected at the field sites; (b) metadata; and (c) explanation of any deviations from data collection protocols. This database shall be submitted with the final report.


Task 7. Develop methodology(ies) for evaluating the operational performance and assessing safety effects of weaving sections on arterials.


Task 7a. Develop and validate operational performance evaluation methodology(ies). Each methodology developed herein for arterial weaving sections shall be: (a) quantitative; (b) general enough to estimate the performance measures of the arterial weaving sections; and (c) suitable for inclusion in future updates to the HCM.


Task 7b. Characterize safety effects of varying conditions in arterial weaving sections. Develop an approach for characterizing the safety effects of varying geometric, volume, and traffic control conditions. Identify additional research to develop methodologies suitable for the Highway Safety Manual.


The products of Tasks 7a and 7b shall be a technical memorandum on the methodology(ies) developed and validation thereof. This memo shall be presented to and subsequently discussed with NCHRP by web conference.


Task 8. Develop instructional materials for dissemination. Provide and document a computational engine, as defined by the HCM, for implementing the operational methodology. This documented engine should include at least two sample problems to illustrate application of the methodology. A scripted PowerPoint presentation explaining the mechanics of the computational engine shall also be provided.


Task 9. Submit final report. A final report including the findings and deliverables from Tasks 1 to 8 shall be provided.


Note: Following receipt of the draft final deliverables, the remaining three (3) months shall be for NCHRP review and comment and for research agency preparation of the final deliverables.

Research in Progress

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