Traffic Engineering Resources

Convener: Abbas Mohaddes, Econolite

Convener: Paul St.-Aubin, Transoft Solutions

Conveners: Joseph Gregory, FHWA and Ed Fok, FHWA

Convener: Rudy Umbs, P.E., RSP2I, Tindale Oliver

FHWA's Eddie Curtis answers the question: I am a Traffic Engineer with an Agency with 20 (or Fewer) Signals and We Have Funding to Upgrade Them. Where Do I Start?

Since the yellow indication was first added to traffic signals in 1920, the proper interval duration has been robustly debated.1 Seemingly, the timing of the yellow indication appears straightforward. However, determining the illumination interval is quite intricate since it is part of a complex system of physical and human-made laws, technology, and human behavior that all must operate compatibly.

The critical distance is the foundation to Gazis, Herman and Maradudin's (GHM) universally adopted minimum yellow traffic signal timing solution presented in their 1960 paper, "The Problem of the Amber Signal Light in Traffic Flow" [1]. However, GHM's (permissive [2]) minimum yellow signal duration is limited in its application since they only accounted for vehicles moving at constant velocity traversing a minimum safe and comfortable stopping distance referenced a level intersection's stopping line, aka GHM's critical distance.

ITE has concluded a years-long effort to issue guidance on yellow change and red clearance intervals for signalized intersections. The final version of the Recommended Practice Guidelines for Determining Traffic Signal Change and Clearance Intervals (RP-040B) has been adopted by the ITE International Board of Direction and is now available.1

The Institute of Transportation Engineers (ITE) has issued guidance on yellow change and red clearance intervals for signalized intersections. The recommended practice -- Guidelines for Determining Traffic Signal Change and Clearance Intervals -- has been adopted by the ITE International Board of Direction and is now available for purchase.

Yellow change and red clearance intervals have been a topic of research for at least the last 60 years. It would be easy to assume that we now know all we need to know about the subject and that the remaining challenge is merely to put what we know into practice. But there is still much about driver behavior at intersections during traffic signal changes that we don't know with certainty or completely understand. During the development of the ITE Guidelines for Determining Traffic Signal Change and Clearance Intervals Recommended Practice, current knowledge, research, and practice in this area was documented, but the following 11 areas of interest were identified where additional study or new research is needed to expand the body of knowledge. Research in these areas would be useful in further refining the concepts and procedures in the ITE Recommended Practice.

This discussion will review various models of drivers approaching an intersection in both through and turning lanes and what yellow change interval may be necessary in those situations. It is an extension of the work of Gazis, Herman, and Maradudin's (GHM) in their seminal 1960 paper, "The Problem of the Amber Signal Light in Traffic Flow". GHM proposed the basic protocol used today for setting a minimum yellow change interval for through movements that would provide a motorist with a solvable solution to the stop or go problem encountered when the yellow signal is illuminated.

As engineers, we are highly trained to identify a need or problem, solve it, and then iteratively improve it into a better "product" (e.g., solution, device, process). Typically, the product is then sold to customers. We can refer to this as the "push" of the solution, when we develop a product and push it into the market and onto society. Engineers practicing street design "push" their designs onto society, which is rooted in the practices and values from the 1950s and 1960s. What if we instead followed a "pull" methodology, where a street is designed to meet the desires and preferences of a wide range of customers or user groups? This would be analogous to the process that evolved in the automotive industry.

This White Paper first discusses the efforts of the pioneering states in mitigating WWD incidents; the paper then documents the efforts FDOT has undertaken to tackle the WWD problem in Florida. The FDOT's strategy pertaining to the statewide policy, several WWD-related research projects, and pilot WWD countermeasure implementation projects, etc., are discussed in detail. This document also provides a brief overview of the ongoing and recently completed research efforts. This White Paper will assist other agencies in the U.S. and around the world to strategically address the WWD issue.

Interchanges are critical elements of freeway and highway systems that provide access to nearby urban, suburban, and rural areas. Since the development of the interstate highway system in the 1950s, crashes associated with driving in the wrong direction on freeways have created a critical issue for transportation agencies. Wrong-way driving (WWD) occurs when a driver, either inadvertently or deliberately, drives in the opposing direction of traffic along a high-speed, physically divided highway or its access ramp. Reasons a driver may go in the wrong direction include but are not limited to, driving under the influence of substances such as alcohol or drugs, fatigue, and a confusing geometric roadway design. WWD crashes are known for their tendency of being more severe than other types of freeway crashes, which result in more fatalities due to them being mostly head-on or opposite-direction sideswipe collisions. According to the National Highway Traffic Safety Administration (NHTSA) Fatality Analysis Reporting System (FARS) database, during 2004 to 2011, an average annual total of 359 people perished in 269 fatal WWD crashes. This means that the average number of fatalities per WWD fatal crash was 1.33, as compared to the 1.09 death rate for all other fatal motor vehicle crashes, thus necessitating further evaluation and action.

Big Results with a Mini Roundabout - Webinar Question Log

ITE GRADE CROSSING STANDING COMMITTEE 102-02 Draft Meeting Minutes August 21, 2018

High-Speed Rail: What Does America's Largest Public Works Project Mean for Transportation Planners and Engineers?

Designing New Features to Control Right-Turn on Red