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This report is an archived publication and may contain dated technical, contact, and link information
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Publication Number:  FHWA-HRT-19-025    Date:  March 2019
Publication Number: FHWA-HRT-19-025
Date: March 2019

 

Simulator Assessment of Alternative Lane Grouping at Signalized Intersections

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FOREWORD

The Federal Highway Administration (FHWA) is focused on improving highway design by increasing knowledge of how intersection design affects operational efficiency and safety. Two intersection configurations designed to increase capacity without adding lanes are the dynamic reversible left-turn lane at diamond interchanges and contraflow left-turn lane at signalized intersections. These intersection configurations were explored in the project Simulator Assessment of Alternative Lane Grouping at Signalized Intersections. This project consisted of two studies, both conducted in FHWA's Highway Driving Simulator, that assessed driver behavior and comprehension in response to signs and symbols used to convey reversible-lane operations.

This report is of interest to engineers, planners, and transportation professionals concerned with implementing signs and pavement treatments for alternative intersections and responsible for highway design and public safety.

Brian P. Cronin, P.E.
Director, Office of Safety Research and
Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation (USDOT) in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

Technical Report Documentation Page
1. Report No.
FHWA-HRT-19-025
2. Government Accession No. 3. Recipient’s Catalog No.
4. Title and Subtitle
Simulator Assessment of Alternative Lane Grouping at Signalized Intersections
5. Report Date
March 2019
6. Performing Organization Code
7. Author(s)
Stephanie M. Roldan, Tracy B. Gonzalez, and Vaughan W. Inman
8. Performing Organization Report No.
9. Performing Organization Name and Address
Leidos, Inc.
6300 Georgetown Pike
McLean, VA 22101
10. Work Unit No. (TRAIS)
11. Contract or Grant No.
DTFH61-13-D-00024
12. Sponsoring Agency Name and Address
Office of Safety Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101
13. Type of Report and Period Covered
Technical Report; February 19, 2016-March 30, 2018
14. Sponsoring Agency Code
HRDS-30
15. Supplementary Notes
The Contracting Officer's Representative (COR) was Brian Philips (HRDS-30). The Task Order COR was Michelle Arnold (HRDS-30).
16. Abstract
Throughput during peak-period traffic at signalized intersections with high left-turn demand commonly creates a bottleneck. Two intersection configurations designed to increase the capacity at locations without adding lanes are the dynamic reversible left-turn (DRLT) lane at diamond interchanges and contraflow left-turn (CLT) lane at signalized intersections. The DRLT design replaces back-to-back left-turn bays with reversible lanes that span the distance between interchange nodes. The direction of flow alternates within a signal cycle. Signals and changeable-message signs control the direction of flow. The DRLT configuration may result in drivers intending to make a left turn at the downstream ramp viewing opposing traffic in the lane they are to use in a subsequent signal phase. In a CLT intersection, a gap in the median allows drivers turning left to queue in a lane that is normally used by opposing through traffic. The CLT design allows for an additional left-turn lane without widening the roadway. Two experiments, conducted in a highway driving simulator, evaluated driver comprehension and lane usage in DRLT and CLT intersections compared to conventional intersections, which were also simulated. Data were obtained from 96 participants in each experiment. The results of the DRLT interchange experiment showed that up to 25 percent of participants made inappropriate lane changes when first encountering the DRLT lane and observing opposing traffic in their lane prior to receiving a green signal. Early signs of confusion dissipated in later trials, such that only 4 percent of participants made more than 1 inappropriate lane change in the DRLT interchange. Participants in the CLT-intersection experiment used the CLT lane more frequently after the first encounter, with probability of use rising to 58 percent during the second exposure when there was a long queue in the nonreversible left-turn lane. Lane changes in the CLT intersection were uncommon and occurred in only 5 percent of trials. Under some circumstances, however, acceleration- and brake-release delays were longer in the CLT intersection than in the conventional intersection configuration. These delays did not improve during the second exposure. Findings show that signs and markings used in both studies will work well in a real-world environment. Recommendations are provided for additional and modified signs and markings on the approach sides of DRLT and CLT intersections to improve comprehension and comfort of drivers who may see opposing traffic in their lane while waiting for a green signal.
17. Key Words
Dynamic reversible left-turn interchange, diamond interchange, contraflow left-turn interchange, reversible lanes, signs, markings, driver behavior, driving simulation
18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.
https://www.ntis.gov
19. Security Classif. (of this report)
Unclassified
20. Security Classif. (of this page)
Unclassified
21. No. of Pages
74
22. Price
N/A
Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized.

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