ITE Journal - March 2020 - 6

| director's message
Holly Gilbert Stowell

How Hard Can That Be?
Let's imagine that, at a neighborhood party, I tell one of my
friends that ITE had been working on a recommended practice
on clearance intervals. Once I got past explaining to him or her,
"This means determining how long the yellow (and sometimes all
red) light stays on at a signal," I am pretty confident the reaction I
would get is, "How hard can that be?"
Assuming that they didn't immediately walk away to find a
more interesting conversation, I might ask-Should the signal be
timed for your 18-year-old son or 85-year-old mother? Should we assume the driver is
paying attention, or distracted in some way? Will the driver be going below, at, or above
the speed limit when they have to make a decision to stop or go? Will the vehicle be going
straight through the intersection or turning? Like many things in life, something that
seems very simple on the surface gets very complex once you start digging in.
This issue of ITE Journal features the release of the ITE Recommended Practice
Guidelines for Determining Traffic Signal Change and Clearance Intervals. This
recommended practice is more than 10 years in the making. Over the last three years we
have published the recommended practice twice for member comment, held an appeals
hearing, and made a number of adjustments and changes. Articles by Doug Noble, P.E.,
PTOE (F) and Jeff Lindley, P.E. (F) highlight key considerations and areas where we
still need more research to fully understand driver behavior at traffic signals. Also included
is an article by Jay Beeber (M), one of the appellants, explaining why he advocated for a
more precise formulation of the theory underpinning clearance interval computations.
In the final recommended practice we have tried to strike a balance between theory
and real world considerations. We adopted the extended kinematic equation as the
most appropriate representation of the physics involved, but we also recognize that
transportation engineers must consider many factors in determining the appropriate
clearance interval at a particular location. We have strongly encouraged the use of data in
making these decisions, particularly in situations like protected left turns at higher speed
intersections where the speed of entering and exiting vehicles and the size and design of
the intersection significantly impact the time needed.
As we work to help all users-drivers, bicycles, pedestrians-get to their destinations
in a timely manner, we have to keep safety at the forefront. Another consideration with
clearance intervals is their relationship to automated enforcement. Given the complexity
involved in setting appropriate clearance intervals, this recommended practice makes a
very clear statement with regard to how aggressive jurisdictions should be in enforcing
red light violations. In conjunction with this recommended practice, the ITE International Board of Direction proposed a new ITE Policy on Automated Enforcement. ITE
strongly supports automated enforcement, not with a goal of raising revenue, but for the
purposes of enhancing safety.
So there you have it. A simple question with a not so simple answer. We hope that this
recommended practice furthers the understanding of appropriate clearance intervals
and incentivizes additional research on the subject. As always you can reach me at or on Twitter: @JeffPaniatiITE.

Jeffrey F. Paniati, P.E. (F)
Executive Director and Chief Executive Officer

Ma rch 2020

i te j o urnal

Senior Editor and Writer

Pam Goodell

Marketing Senior Director

Content Worx
Design and Production

Jeffrey F. Paniati, P.E. (F)

Executive Director and Chief Executive Officer

Kathi P. Driggs, IOM

Associate Executive Director and Chief Operating Officer

Jeffrey A. Lindley, P.E. (F)

Associate Executive Director and Chief Technical Officer

Sonya Torres

Accounting Specialist

Marche Curry

Administrative Specialist

Ann O'Neill

Certification Programs Manager

Tatiana Richey

Contracts Manager

Zach Pleasant, PMP

Information Technology Services Senior Director

Douglas E. Noble, P.E., PTOE (F)

Management and Operations Senior Director

Linda S. Pierre, CMP, CEM
Senior Director of Meetings

Eunice Chege Thoya

Membership Associate

Jennifer Childs

Membership Database Associate-Data Services

Sallie C. Dollins

Membership Services Associate

Kellyanne Broom

Professional Development Manager

Colleen A. Agan

Senior Director of Membership Strategies and Operations

Kevin G. Hooper, P.E. (F)

Strategic Projects (Consultant)

Nicola Tavares, PMP

Technical Products Manager

Niloo Parvinashtiani

Technical Programs Associate

Sarah Abel (M)

Technical Programs Manager

Deborah L. Rouse

Technical Publications Manager

Lisa M. Fontana Tierney, P.E. (F)
Traffic Engineering Senior Director

Siva R. K Narla (M)

Transportation Technology Senior Director

Volume 90  |  Issue 3
ITE Journal (ISSN 0162-8178) is written by and for transportation engineers,
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ITE Journal - March 2020

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