Traffic signal yellow times could begin rising at intersections throughout the country next year. The Institute of Transportation Engineers (ITE) expects to have a proposal in early 2020 to address the problem of overly short yellow times for motorists making left-hand or right-hand turns. An ITE panel concluded in September that a team of engineers who objected to the practice were right on the fundamental issue: drivers approaching an intersection to make a turn under certain conditions can neither safely stop nor legally proceed without risking an automated ticket.

Engineers typically refer to this situation as the "dilemma zone" because it places motorists in an uncomfortable position of choosing between two bad options. As documents released in a 2001 California court case show (read documents), red light camera companies intentionally seek out locations with a dilemma zone because of the increased violation volume. ITE does not wish to be associated with automated ticketing.

"The recommended practice is not intended to declare, at a snap shot in time, if a vehicle 'has violated the red signal' and the use of this document and red light running enforcement should be at best loosely connected," the ITE appeal panel concluded in September. "Change intervals are not designed to directly correlate with the exact requirements of red light cameras. Separate guidance on specific enforcement tolerances should be provided based on further study and research, not included as part of the recommended practice."

A congressional report (view document) in 2001 accused ITE of changing its practices over time in a way that reduced yellow times. The result, in the wording of the ITE's own 1994 task force, was that "enforcement can be used instead" of the longer yellow time.

Jurisdictions implementing ITE's formula often use the absolute minimum amount of yellow possible, and this even a tiny shortening of the yellow can have a massive impact on the number of violations. A study by the Texas Transportation Institute explained that the majority of straight-through red light violations happen when a driver misjudges the end of the yellow light by less than 0.25 seconds (view chart). The TTI study also confirmed that longer yellows also reduced accidents (view report).

With that in mind, the team of engineers that successfully challenged ITE's formula for determining yellow time using a mathematical proof. They demonstrated that the formula does not leave enough time for individuals who approach an empty left-turn lane at the posted speed limit.

They backed up their theory with data collected during a live vehicle dynamics demonstration. A traffic light was set up with the ITE's minimum recommended 3.2 second right-turn yellow, which was triggered when the test car came within 141 feet of the intersection. The test subjects ran into trouble when they attempted to make turns.

"The data clearly shows that ITE's yellow timing solution cannot be applied to turning lanes or anywhere a driver in a vehicle is in need of deceleration prior to entering an intersection," Oregon engineer Mats Jarlstrom explained.

Jarlstrom was joined in his appeal by Safer Streets LA executive director Jay Beeber, North Carolina professional engineer Brian Ceccarelli, and the National Motorists Association's professional engineer Joe Bahen.

The US Department of Transportation and several states recognize ITE standards as authoritative. As a result, ITE has a specific process for revising its recommended practices. After ITE staff develop the changes identified by the appeals panel, ITE's sixteen-member board of directors will vote on whether to adopt the recommended fixes.