ITE Journal – December 2019 - 42

Peak Period Delay Analysis

Acknowledgments

In the delay analysis, delay reduction for dynamic flashing yellow
arrow operations along with weighted average delay reduction
for dynamic flashing yellow arrow operations are being analyzed.
When always operating protected only, the average delay when the
approach was operating protected only was used.
The analysis of the peak period delay was done manually
through the traffic video from the CCTV camera by analyzing
stopped and nearly stopped vehicles in 15-sec. bins. Tables
2 and 3 show the delay analysis, and Table 4 shows the delay
reduction analysis.
Tables 2 and 3 show a significant reduction in average delay
per vehicle for flashing yellow arrow operation when compared
to protected only operation. Overall, only 15.8 percent of the
northbound left turn vehicles (16.8 percent of the southbound
left turn vehicles) had to wait longer because of protected only
operations, when compared to the previous 100 percent. If the
left turns were operated protected only by time of day, but stayed
dynamic flashing yellow arrow for the MID Peak, the percentage
would go up to 63.8 percent for northbound left turns and 54.6
percent for southbound left turns (more than three times more).
Overall, in three days, the northbound left turn had a total delay
reduction of 25.6 hours and the southbound left turn had a total
delay reduction of 20.1 hours. This would amount to a potential
reduction of up to a yearly 1,331.2 hours of delay for the northbound
left turn and a potential reduction of up to a yearly 1,045.2 hours of
delay for the southbound left turn. The average delay reduction per
vehicle for northbound and southbound left turns varies from 26.3
sec./vehicle to 56.1 sec./vehicle. According to the Highway Capacity
Manual, this can cause a multiple level of service (LOS) reduction.6

This traffic signal modification and study was supported by the
Wisconsin Department of Transportation (WisDOT). The traffic
signal controllers were purchased by WisDOT through Traffic
Control Corp. and supported by Traffic Control Corp., and
Econolite Group, Inc.

Conclusion
The new dynamic flashing yellow arrow methodology uses existing
features on Econolite controllers, and is still conforming to
common National Electrical Manufacturers Association standards.
The CCTV camera showed drivers making good gap decisions. The
northbound left turn had a total delay reduction of 25.6 hours and
the southbound left turn had a total delay reduction of 20.1 hours.
The delay reduction per vehicle can cause a multiple LOS reduction.
In future traffic studies of dynamic flashing yellow arrows, it
would be beneficial to analyze how the left turn queue length values
would change with intersection geometrics or whether the left turn
is a signal lane or dual lanes. In addition, the analysis of thresholds
is needed and how it interacts with different variables. WisDOT
is going to closely monitor the crash history of this intersection as
time progresses. It is expected that the number of intersections that
operate with this methodology will increase at WisDOT due to the
reductions in delay, and the positive feedback from the public. itej
42

D ecem ber 2019

i t e jo u rn al

References
1. Wisconsin Department of Transportation. Traffic Signal Design Manual.
Bureau of Traffic Operations. http://wisconsindot.gov/dtsdManuals/
traffic-ops/manuals-and-standards/tsdm/03/03-04-01.pdf [Accessed
May 22, 2017]
2. Brehmer, C. L., K. C. Kacir, D. A. Noyce, and M. P. Manser. NCHRP Report
493: Evaluation of Traffic Signal Displays for Protected/Permissive Left-Turn
Control. Transportation Research Board, Washington, DC, 2003.
3. Wisconsin Department of Transportation. Flashing yellow arrows. Bureau
of Traffic Operations. http://wisconsindot.gov/Pages/safety/safety-eng/
flash-yellow.aspx [Accessed May 22, 2017]
4. Davis, G. A., J. Hourdos, and V. Moshtagh. Development of Guidelines for
Permitted Left-Turn Phasing Using Flashing Yellow Arrows. Minnesota Traffic
Observatory, University of Minnesota, Minneapolis. http://www.dot.state.
mn.us/trafficeng/signals/worksheets/MnDOT2015-27.pdf [Accessed May
25, 2017]
5. Fehon, K., M. Krueger, J. Peters, R. Denney, P. Olson, and E. Curtis. Model
Systems Engineering Documents for Adaptive Signal Control Technology
Systems - Guidance Document. Publication FHWA-HOP-11-027. FHWA,
Washington, DC, 2012.
6. Transportation Research Board. Highway Capacity Manual, 2010 Edition.
Washington, DC, 2010.

Justin R. Effinger, P.E. (M) is a principal engineer with
the Lake County Division of Transportation (LCDOT)
in Illinois, USA and is an expert in the field of traffic
signal and Intelligent Transportation System (ITS)
operations. Prior to joining LCDOT, he was a traffic
signal engineer at the Wisconsin Department of Transportation
Southeast Region, providing innovative traffic signal solutions. He
received a bachelor of science in civil engineering and a master of
science in engineering from the University of Wisconsin-Milwaukee.

http://www.wisconsindot.gov/dtsdManuals/traffic-ops/manuals-and-standards/tsdm/03/03-04-0.pdf http://www.wisconsindot.gov/dtsdManuals/traffic-ops/manuals-and-standards/tsdm/03/03-04-0.pdf http://www.wisconsindot.gov/Pages/safety/safety-eng/flash-yellow.aspx http://www.wisconsindot.gov/Pages/safety/safety-eng/flash-yellow.aspx http://www.dot.state.mn.us/trafficeng/signals/worksheets/MnDOT2015-27.pdf http://www.dot.state.mn.us/trafficeng/signals/worksheets/MnDOT2015-27.pdf

ITE Journal – December 2019

Table of Contents for the Digital Edition of ITE Journal – December 2019