July 26, 2019
On Thursday, July 25th, DDC High School Interns Kyle Chan and Alyssa Yamraj gave a presentation to employees and fellow interns on traffic signal warrant analysis. Together they explained the process that goes into a traffic warrant analysis like intersection controls, conditional diagraming, and field observation reporting
Kyle explained the role of the Intersection Control Unit (ICU) at the NYC Department of Transportation. He noted the unit conducts engineering studies to determine the need for additional control devices such as traffic signals, pedestrian signals, and all-way stop controls. Factors such as vehicular/pedestrian volume, crash experience, vehicular speed, visibility and signal spacing are all taken into consideration in the determination process. This was followed by a review of the traffic warrant analysis process. An Intersection Control Study is performed after a review all agency records (e.g. sign orders, pavement marking orders, school maps) for the location being analyzed. Manual or video counts of the number of vehicles and pedestrians in a target area are conduced, usually early in the morning or in the evenings during peak hours. The counts include the number of turning vehicles. At designated school crossings, the number of safe crossing opportunities for school children is determined by recording the frequency and adequacy of gaps between vehicles.
The Conditional Diagrams show street and sidewalk widths, location geometry, street directions, location, as well as conditions of DOT signs and markings, land use, street furniture, distance to the nearest traffic control device, and other information. Alyssa discussed Field Observation Reports which include drivers' compliance with existing controls, geometric or sight distance issues, and violations of the speed limit. She also explained the multiple programs utilized by inspectors or consultants when conducting an engineering study. Kyle and Alyssa closed the presentation providing an overview of the nine traffic signal warrants and how that impacts the intersecting streets of New York City.