Comparison of the Green Arrow and the Circular Green for Turn Prohibition to Reduce Wrong-Way Movements at Interchange Terminals

Comparison of the Green Arrow and the Circular Green for Turn Prohibition to Reduce Wrong-Way Movements at Interchange Terminals Jin Wang Department of Civil Engineering Auburn University March 27, 2017

Auburn University Samford Hall in the Spring.

Auburn University

Introduction How did wrong-way driving (WWD) happened? Entering from an exit ramp.

Motivation Some traffic agencies have replaced Circular Greens (CGs) with Green Arrows (GAs) to provide better lane-use indications to deter wrong-way left turns or right turns at signalized interchange terminals. However, the effectiveness of the strategy has not been well studied. Exit Ramps

Research Objective The study is to compare the Green Arrow and the Circular Green for turn prohibition use to reduce wrong-way movements at interchange terminals.

Comparison of steady green signals by turn-prohibition and WWD-prevention effectiveness Five commonly-used combinations of steady green signals (i.e. Green Arrow and Circular Green/Circular Green) with turn-prohibition (i.e. No Left/Right Turn and One Way) signs

Meaning of the Signal indication The Circular Green Signal Indication : Vehicular traffic facing a Circular Green signal indication is permitted to proceed straight through or turn right or left or make a U-turn movement except as such movement is modified by laneuse signs, turn prohibition signs, lane markings, roadway design, separate turn signal indications, or other traffic control devices. (MUTCD and Uniform Vehicle Code for Drivers by NCUTLO)

Meaning of the Signal indication The Green Arrow Signal Indication : Vehicular traffic facing a Green Arrow signal indication that displayed alone or in combination with another signal indication is permitted to cautiously enter the intersection only to make the movement indicated by such arrow, or such other movement as is permitted by other signal indications displayed at the same time. Refer to Manual on Uniform Traffic Control Devices(MUTCD )and Uniform Vehicle Code for Drivers by the National Committee on Uniform Traffic Laws and Ordinances (NCUTLO)

Data Collection Method: Survey and Interview Data: One public driver survey assessed drivers comprehension and preferences between GA and CG indications. One general WWD traffic agency survey gathered information of GA usage as a WWD countermeasure from agencies involved in WWD research. One comprehensive traffic agency survey obtained traffic agencies current practices and opinions, regarding GAs and CGs for lane-use indications. Interviews were further conducted for response clarification from participants.

Public Drivers Survey To assess drivers comprehension and preferences between GA and CG indications Solicit from different ages, genders, races, and education An information letter served as the cover page and documentation of consent Basic explanations of the research objective Research questions, the recruitment method How data would be collected and protected

Public Drivers Survey Cont. Contain 10 questions Take 5-10 minutes to complete Completely anonymous Distributed online by email with the link to survey 273 responses

Survey Content Public Drivers Survey Cont. The first six questions collected participants demographics Gender, age, nationality, race, education, and US licensed driver or not. The next three questions tested drivers comprehension of GAs and CGs by asking if they can make turning movement when facing the three signal displays shown in a Figure on next slides, i.e. CGs with turn-prohibition signs, GAs only, and GAs with turn-prohibition signs.

Illustrations of Circular Greens for turn-prohibition use

Illustrations of Green Arrows for turn-prohibition use

Survey Content Public Drivers Survey Cont. The last question inquired drivers preference among the three displays as a better indication of correct movements when presented.

Public Drivers Survey Cont. Data Analysis and Results 273 responses from a demographically well-balanced population of participants. (Details omitted) Drivers comprehension For indications given by CGs with turn-prohibition signs, 95.63% of participants had no trouble understanding and making the intended movements, 23.56% did not understand GAs displayed alone enough to make correct turning decisions. When supplemented with turn-prohibition signs, the GA was able to be understood by all

Public Drivers Survey Cont. Data Analysis and Results cont. Drivers preferences 11.99% Green Arrow with no-turn signs 10.26% Green Ball with no-turn signs 17.79% 59.96% Green Arrow only No preference

WWD Traffic Agency Survey To gather information of GA usage as a WWD countermeasure from agencies involved in WWD research To indicate a notion of the preference for steady green signals as a countermeasure of WWD from expert opinions and past experience

WWD Traffic Agency Survey Cont. Surveyed representatives from the 2013 National WWD Summit A group of active WWD researchers and practitioners from the National Transportation Safety Board (NTSB), Federal Highway Administration (FHWA), American Traffic Safety Services Association (ATSSA), Illinois State Toll Highway Authority, state departments of transportation (DOTs), state police and highway patrols, universities, and consulting firms.

WWD Traffic Agency Survey Cont. Survey Content One question regarding traffic signal use for WWD prevention is Does your state use GAs as traffic signal indications at the intersection of exit ramps and crossroads instead of CGs to create a better understanding of the correct movement direction? This question is part of a comprehensive WWD survey at the National WWD Summit.

WWD Traffic Agency Survey Cont. Data Analysis and Results 16 state DOT representatives out of 26 participating states Including Georgia, Illinois, Michigan, Alabama, Texas, Missouri, Massachusetts, Connecticut, Florida, South Carolina, Mississippi, California, Kentucky, Oregon, Rhode Island, and North Carolina. The survey revealed that 38% of participating states have used GAs at interchange terminals to deter WWD. Representatives mentioned to implement Green Arrows statewide and to unify traffic signals to reduce drivers confusion. For instance, the Rhode Island DOT replaced all CGs with GAs at all the interchange terminals in the state in 2014 immediately after the Summit.

Comprehensive Traffic Agency Survey To collect details about current and emerging practices employed by different traffic agencies regarding the use of GAs versus CGs to reduce WWD at interchange terminals To obtain traffic agencies current practices and opinions, regarding GAs and CGs for lane-use indications Surveyed personnel on the National Safety Engineers List and state DOT traffic engineers Contain 15 questions Take 5-10 minutes to complete

Comprehensive Traffic Agency Survey Survey content Cont. Questions on agencies application and preferences of steady green signals and turn-prohibition signs for dedicated through lanes Regarding size and type, the order and placement manner, installation cost, and application circumstances Information on the guidelines of GAs and CGs the agency are using Opinions of GAs and CGs related causes and suggested countermeasures for WWD at terminals

Comprehensive Traffic Agency Survey Survey content cont. Cont. Questions on agencies application and preferences of steady green signals and turn-prohibition signs for dedicated through lanes Regarding size and type, the order and placement manner, installation cost, and application circumstances Information on the guidelines of GAs and CGs the agency are using Opinions of GAs and CGs related causes and suggested countermeasures for WWD at terminals

Comprehensive Traffic Agency Survey Cont. Survey content cont. Rank the five combinations of the steady green signals given five real-world examples (Figures follow). GA + turn-prohibition sign (LED) GA + regular turn-prohibition sign GA Only CG + turn-prohibition sign (LED) CG + regular turn-prohibition sign

Comprehensive Traffic Agency Survey Cont. Survey content cont. Rate the overall performances GA + turn-prohibition sign (LED) GA + regular turn-prohibition sign GA Only CG + turn-prohibition sign (LED) CG + regular turn-prohibition sign

Example: Green Arrow + turn-prohibition sign (LED) Image: Image: Mahdi Huaguo Pour Rouholamin Zhou Chicago, IL

Example: Green Arrow + turn-prohibition sign (Regular) Image: Jin Wang Birmingham, AL

Example: Green Arrow Only Nighttime Image: Jin Wang Daytime Image: Jin Wang Montgomery, AL

Example: Circular Green + turn-prohibition sign (LED) (turn-prohibition signs shall be mandated, not optional) Location 2 Image: Huaguo Zhou Location 1 Image: Huaguo Zhou Chicago, IL

Example: Circular Green + turn-prohibition sign (Regular) (turn-prohibition signs shall be mandated, not optional) Nighttime Image: Jin Wang Daytime Image: Jin Wang Image: Jin Wang Montgomery, AL

Comprehensive Traffic Agency Survey Cont. Data Analysis And Results Participated by 73 representatives from 12 states Alabama, Georgia, Massachusetts, Connecticut, Iowa, Illinois, Idaho, Ohio, Missouri, Michigan, Pennsylvania, and North Carolina GAs are used just as commonly as CGs. Driver Manual Green Arrow Installed 100% 50% 55% 36% 45% 64% 0% Yes No

Comprehensive Traffic Agency Survey Cont. Data Analysis And Results cont. GAs are used just as commonly as CGs. The installation and maintenance costs are about the same. It is very cheap and easy to replace CGs with GAs. MUTCD is the only guideline they use for the installation and application of traffic signals and supplemental signs. Factors that may influence the effectiveness: the visibility of supplemental signing and marking has significant influence.

Comprehensive Traffic Agency Survey Cont. Data Analysis And Results cont. Ranking the turn-prohibition use of GAs and CGs based only on WWD prevention effectiveness NO.1. GA + turn-prohibition sign (LED) NO.2. GA + turn-prohibition sign (Regular) NO.3. CG + turn-prohibition sign (LED) NO.4. CG + turn-prohibition sign (Regular) NO.5. GA only

Comprehensive Traffic Agency Survey Cont. Data Analysis And Results cont. Rating the overall performance of GA and CG displays considering all possible impact factors Scores were given on a scale from 1 to 5 (1= unacceptable; 2= fair; 3= good; 4= very good; 5=excellent). Higher scores indicate better performances.

Comprehensive Traffic Agency Survey Cont. Rating: each cell is the average of all participants ratings. Variable CG + turnprohibition sign (LED) CG + turnprohibition sign (Regular) GA only GA + turnprohibition sign (LED) GA + turnprohibition sign (Regular) Equipment Cost 2.6 4.0 4.4 2.6 4.0 Understandability 3.9 3.4 2.9 4.4 4.1 Visibility 4.3 3.7 3.6 4.8 3.9 Current Popularity 2.4 4.3 2.7 2.3 3.1 Response 3.8 3.4 2.9 4.3 4.3 Complexity Perception time 3.9 3.4 3.0 4.5 4.0 Conformity 2.6 3.4 2.6 3.0 3.2 Easiness of 2.8 4.2 4.3 3.0 4.0 Implementation Existing Education Materials 2.6 2.8 2.0 2.0 2.2

Comprehensive Traffic Agency Survey Cont. Data Analysis And Results cont. By summing up ratings of the variables: Understandability, Visibility, Response Complexity, and Perception time, which are directly affects driver behavior, the overall ratings from the highest to lowest are: 18 for GA + turn-prohibition sign (LED) 16.3 for GA + turn-prohibition sign (Regular) 15.9 for CG + turn-prohibition sign (LED) 13.9 for CG + turn-prohibition sign (Regular) 12.4 for GA only. This rating is consistent with the agencies ranking results based only on WWD prevention effectiveness

Conclusions And Recommendations Replacing CGs with GAs can help prevent WWD at interchange terminals. Turn-prohibition signs should complement GAs to enhance its performance and driver comprehension. LED turn-prohibition signs can be used with GAs at lowlight, under-bridge, and high-crash-risk locations.

Conclusions And Recommendations Recommendation on application and installation circumstances from best to worst based on turn-prohibition and WWD-prevention effectiveness: 1. GA + turn-prohibition sign (LED): applied to complicated high traffic volume intersections, especially in one-way, low-light conditions (e.g., interchange terminals, urban one-way crossroad intersections). 2. GA + regular turn-prohibition sign: applied to complicated and standard intersections, especially for one-way crossroad intersections.

Conclusions And Recommendations Recommendation cont.: 3. CG + turn-prohibition sign (LED) (Turn-prohibition signs shall be mandated, not optional): applied to standard intersections, especially in low-light conditions. 4. CG + regular turn-prohibition sign (Turn-prohibition signs shall be mandated, not optional): applied to standard intersections in good lighting conditions. 5. GA Only: applied to low traffic volume intersections, especially in one-way-crossroad and good lighting conditions.

Thank you! Q & A Jin Wang jinwang@auburn.edu