Suggested reading
National Cooperative Highway Research Program (NCHRP) Report 731 Guidelines for Timing Yellow and All-Red Intervals at Signalized Intersections Published July, 2012.
Project 03-95 Panel - Field of Traffic - Area of Operations and Control

ISSN 0077-5614

ISBN 978-0-309-25859-3

Library of Congress Control Number 2012949147
- National Academy of Sciences.
- National Academy of Engineering
- The Institute of Medicine
- The National Research Council
- The Transportation Research Board
Forward
Yellow and all-red interval duration is a significant factor affecting the frequency of red-light running, yet there remains no national consensus on how the yellow and all-red intervals should be timed for safe and efficient operations.
Studies of driver reaction times and vehicle deceleration rates used in determining appro- priate yellow and all-red change intervals were conducted more than 25 years ago
This information was analyzed to develop draft yellow change and all-red clearance interval guidelines, which were submitted to NCHRP and the key stakeholder groups for review and comment. Comments were addressed to produce a final report to document the research effort and the stand-alone, proposed guidelines for timing yellow and all-red intervals.
Summery
The objective of this research was to develop a comprehensive and uniform set of recommended guidelines for determining safe and operationally efficient yellow change and red clearance intervals at signalized intersections.
The amount of time that the yellow signal is displayed is referred to as the yellow change interval. The duration of this interval is based on the drivers perception-reaction time and deceleration rate, the approach speed, and the approach grade. The duration of the yellow change interval should allow, at a mini- mum, for a driver to comfortably decelerate to a stop prior to entering the intersection.
Over time, several national publications have served as references for the timing of change intervals. These include:
- Manual on Uniform Traffic Control Devices
- Traffic Engineering Handbook
- Manual of Traffic Signal Design
- Traffic Control Devices Handbook
- Traffic Signal Timing Manual.
Yellow and all-red interval duration is a significant factor affecting the frequency of red-light running.
Yellow and all-red intervals should be timed for safe and efficient operations.
The amount of time that the yellow signal is displayed is referred to as the yellow change interval.
To verify that accurate values were being used in the timing of these intervals, an extensive field investigation of driver behaviours was conducted.
The field investigation focused on three parameters directly related to the use of the kinematic equation:
(1) perception-reaction time,
(2) deceleration rate, and
(3) approach speed.
Body:
The field investigation captured data from over 80 intersection approaches in five different states. The states were selected in different regions of the country to provide the regional diversity necessary to account for variations in timing practices as well as factors such as driver age, familiarity, grade, and red-light camera enforcement.
Using a high-definition camera mounted atop a modular 20-foot-tall aluminum pole, over 320 hours of video were obtained. From this video, approximately 7,500 vehicles were extracted as data points for the evaluation portion of this study.
The analyses were performed using a multi-factor analysis of variance (ANOVA).
The results of the analyses led to the following conclusions:
• The perception-reaction time was confirmed to be 1.0 s.
• The deceleration rate was confirmed to be 10 ft/s2.
Yellow change interval (seconds) by approach speed limit and grade
25mph / 40km - 3.4s - 0 grade
30mph / 48km - 3.7s - 0 grade
35mph / 56km - 4.1s - 0 grade
40mph / 64km - 4.5s - 0 grade
45mph / 72.5km - 4.8s - 0 grade
50mph / 80.5km - 5.2s - 0 grade
55mph / 88.5km - 5.6s - 0 grade