Traffic control devices are all signs, signals, markings and devices placed on, or adjacent to, a street or highway by a public body having authority to regulate, warn or guide traffic.

Traffic engineers promote safer traffic conditions by providing roadway conditions that contribute to smooth and efficient traffic flow.

Experience has shown that safety goes hand in hand with smooth traffic operation. Disrupting the smooth flow of traffic increases the probability of accidents.

Erratic traffic operation may be caused by vehicles stopping or slowing in the roadway, passing and weaving maneuvers, or other surprise elements. For example, unwarranted traffic signals, unreasonably low speed limits and too many signs may cause driver confusion and indecision.

The role of traffic engineers may be compared to that of the medical profession in protecting the public. As trained professionals, traffic engineers look at the symptoms of general traffic conditions, and to make a competent diagnosis, they take traffic counts, analyze accident statistics, study speed data, examine roadway conditions, conduct research and study what other professionals are doing and the results they have achieved.

Traffic engineering is that phase of engineering that deals with the planning, geometric design and traffic operations of roads, streets and highways and their networks, terminals, abutting lands and relationships with other modes of transportation for the achievement of safe, efficient and convenient movement of people and goods.

Traffic engineering applies engineering principles that help solve transportation problems by considering the psychology and habits of the transportation system users.

Active studies, as well as those that are programmed (funded but not yet assigned to a consultant), are listed online in the Research in Progress database. To learn more about these studies:

The FHWA State Planning and Research (SPR) program funds most research projects following the requirements of 23 CFR 420. Those projects are designated as “SPR” plus a project number assigned by the Research Center, e.g, SPR-595.

The ADOT project manager, in cooperation with the sponsor and champion, leads the process of identifying TAC members, developing a scope of work, releasing a solicitation, and selecting a consultant to conduct the study.

The RAC consists of staff from the Research Center, various ADOT Divisions, and the Federal Highway Administration (FHWA). Membership is intended to represent a wide variety of fields and interests within the department. Working in an advisory capacity, members review problem statements for new research and consider recommendations for funding.

A problem statement describes an idea for future research, and is presented to the ADOT Research Advisory Committee for consideration of funding. It briefly states the existing problems to be addressed and the objectives that would be met by the requested research. It does not prescribe a methodology, include a scope of work, or call for the use of specific products or providers. In general, a problem statement raises questions that would be answered by the suggested research, but does not presume to know the answers.

The TAC consists of ADOT subject matter experts, including the sponsor and champion, who critically review the technical content of research deliverables. When appropriate to the study topic, the TAC may also include staff from other public sector agencies. Active participation by TAC members is necessary to ensure that a research study fulfills its objectives.