Findings from Indiana Flashing Yellow Arrow Study. Robert A. Rescot, Ph.D., P.E.

Transcription

1 Findings from Indiana Flashing Yellow Arrow Study Robert A. Rescot, Ph.D., P.E. 1

2 Other Project Staff Shou Qu Graduate research assistant Rebecca Noteboom Undergraduate research assistant Ahmad Nafakh Undergraduate research assistant 2

3 Study Advisory Committee Joe Bruno Mike Holowatty Greg Richards Shuo Li Bill Smith Brad Steckler Jim Sturdevant 3

4 Problem to Address 4 Providing a consistent driver expectation has been a fundamental principal of modern traffic engineering, and is the foundation for the Manual on Uniform Traffic Control Devices (MUTCD). However, traffic signals routinely provide mixed messages at locations having protected/permissive left turns.

5 Conflicting Signal Messages Not the Same Meaning! Left Turn Lane Through Lane 5

6 FYA Operational Benefits Unlocks signal timing options Provides more flexibility for signal design Removes yellow trap Improves safety / reduces crashes 6

7 Alignment with INDOT / FHWA Goals Improve Efficiency Flashing Yellow Arrow Reduce Injuries & Fatalities Reduce Crashes 7

8 FYA Signal Options Signal head options Vertical/Horizontal 4-section Vertical/Horizontal 3-section (Bi-modal) Red options Red ball Red arrow Auxiliary sign options 8

9 First Indiana Implementations 9 Centerville/Richmond, Indiana

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16 16 Vincennes, Indiana

17 17 Notice a Difference?

18 Evaluation of Signal Orientation Options Mixed Orientation Signals? Driver Behavior Observations Driver Surveys Crash Data 18

19 NCHRP Table of Results for Driver Response at FYA Signals 19

20 20 Data Collection

21 21 Data Collection

22 Data Collection Recorded vehicles entering rear of left turn bay when not sight obstructed for observer, and no other proceeding vehicles in the bay to alter driver behavior Vehicle must enter and depart on flashing yellow arrow (or solid green ball at control sites) Speed and time tracked from rear of bay through to crossing the stop line to begin their left turn. Data collected at each FYA site and at similar site in/near each FYA location with Protected/Permitted Left Turn Yield on Green display. 22

23 Data Sample Vincennes FYA Speed-Time Data 23 Speed (mph) Time (sec)

24 Data Sample Vincennes FYA Distance-Time Data Distance (feet) Time (sec)

25 Data Reduction For each vehicle, a linear regression of speed versus time data was performed; first derivative is acceleration (deceleration) 25

26 Data Summary Centerville FYA Centerville Control Vincennes FYA Vincennes Control Sample Size Average Acceleration (Feet/Second 2 ) Standard Deviation of Acceleration

27 Statistical Analysis Derived acceleration values for all observed vehicles at each site (FYA and control in each city, four sites total) were compared using a two sample t-test. Null hypothesis (H O : There is no statistical difference, with 95% confidence, in mean acceleration between each pair of sites. 27

28 T-Test Results 28 Site Centerville FYA Centerville Control Vincennes FYA Vincennes Control Centerville FYA - Centerville Control Do Not Reject H 0 P= Vincennes FYA Do Not Reject H 0 P=0.593 Do Not Reject H 0 P= Vincennes Control Do Not Reject H 0 P=0.887 Do Not Reject H 0 P=0.134 Do Not Reject H 0 P=

29 Driver Surveys 12 Scenarios were visually shown to participants. Each scenario depicted a slightly different dilemma for a driver. The options were the same for each scenario, as a driver wanting to make a left turn they could either choose to GO, YIELD, or STOP. Purdue IRB protocol approval #

30 List of Scenarios 30 Scenario 1: horizontal signal heads; solid green left turn arrow, red ball for through traffic Scenario 2: horizontal signal heads; solid red left turn arrow, red ball for through traffic Scenario 3: horizontal signal heads; solid yellow left turn arrow, green ball for through traffic Scenario 4: horizontal signal heads; flashing yellow left turn arrow, green ball for through traffic Scenario 5: vertical signal heads; [Same as #1] Scenario 6: vertical signal heads; [Same as #2] Scenario 7: vertical signal heads; [Same as #3] Scenario 8: vertical signal heads; [Same as #4] Scenario 9: horizontal left turn and vertical through signal heads; [Same as #1] Scenario 10: horizontal left turn and vertical through signal heads; [Same as #2] Scenario 11: horizontal left turn and vertical through signal heads; [Same as #3] Scenario 12: horizontal left turn and vertical through signal heads; [Same as #4]

31 Survey Results All Horizontal FYA Total Fail Critical Responses: 20 (37.7%) 31

32 32 Scenario 3

33 Survey Results All Vertical FYA Total Fail Critical Responses: 9 (16.9%) 33

34 Survey Results Mixed FYA Total Fail Critical Responses: 10 (18.8%) 34

35 35 Crash Records

36 36 Crash Records

37 Conclusion Implementation of FYA in Indiana has shown results consist (and better than) with many other studies Based on Crash Modification Factor Clearinghouse data, switching from protected to protected/permitted signals should have increased crashes between 34% and 124% There is no reason to believe that using mixed orientation signals has a negative impact on safety. 37

38 INDOT Resources 38

39 39 Comments