How does DOT decide whether a traffic signal should be installed at an intersection?
Traffic engineers examine the existing conditions to decide if a traffic signal is appropriate at each location. They study the number of pedestrians, the traffic flow, the accident history, the possible presence of school children and bicyclists. The engineers evaluate this activity at the intersection to determine if a traffic signal is the best means of controlling traffic at each particular location. If we decide that a traffic signal would not be appropriate at a particular location, we may select another option to control traffic, such as speed humps, speed limit signs, stepped-up traffic enforcement, and Safety City programs. The standards for traffic control devices can be found in the Manual on Uniform Traffic Control Devices, which is published by the Federal Highway Administration.
DOT uses a detailed process called an intersection control study to determine if traffic signals or multi-way stop signs are appropriate for a location. The study includes (but is not limited to) these steps: • DOT inspectors check all agency records (e.g. sign orders, pavement marking orders, school maps) for the location. • A DOT inspector conducts a field investigation to create a Condition Diagram of the location. This diagram shows street and sidewalk widths, location geometry, street directions, location and conditions of DOT signs and markings, land use, street furniture, distance to the nearest traffic control device, and other information. • The inspector completes a Field Observation Report which has a checklist of conditions at the location. This includes drivers’ compliance with existing controls, geometric or sight distance issues, and violations of the speed limit. • DOT inspectors conduct manual counts of the number of vehicles and pedestrians, usually during morning and
