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July/August 2009

Intersection Turning Movement Data

Being able to compile and interpret data on how traffic turns through an intersection could have an impact on future environmental and safety decisions regarding intersection geometry and traffic control. However, until recently no standard has existed to properly obtain and use this data. Now, ASTM International Committee E17 on Vehicle-Pavement Systems has approved E2667, Practice for Acquiring Intersection Turning Movement Traffic Data, a new standard developed by Subcommittee E17.52 on Traffic Monitoring.

“Intersections that do not work well constrain the flow of vehicles and induce higher risk taking because of increased delay,” says Ralph Gillmann, a team leader for the Federal Highway Administration and chair, Subcommittee E17.52. “Within an urban area, intersections commonly have the highest incidence of accidents. Vehicle idling increases emissions and reduces air quality. Improvements to traffic operations, safety and air quality are directly related to understanding and improving vehicle movement at intersections.”

Making improvements to intersections requires the consistent and repeatable monitoring of vehicles at intersections. “While there are standards for monitoring vehicles passing road segments, there was no standard for monitoring vehicle movements at intersections,” says Gillmann. “Through ASTM, this first standard practice for intersection turning movements has been adopted.”

The benefits of understanding vehicle turning movement data are widespread. “If we are concerned about reducing air pollution, improvements to how an intersection accommodates traffic are important because vehicle delays impact pollution,” says David Albright, transportation safety program manager, Bernalillo County Public Works Division, and a longtime E17 member. “If we are concerned about safety, accidents are compared with exposure rates and exposure rates are based on traffic data. Something that appears to be as simple as counting cars, trucks, pedestrians and bicycles at intersections turns out to be critical to our health and well-being.”

According to Albright, the importance of the data and the constraints imposed by the current practice led to the development of the new standard. “ASTM E2667 is the first intersection vehicle turning movement standard, and it continues the tradition of ASTM leadership in traffic data standards.”

Albright notes that there are two ways in which the absence of a standard practice negatively impacts intersection operations and safety. “One way is in the limitation of comparing data within an organization over time. The second way is the limitation of comparing data at the same point in time among different organizations.”

Data managers who supervise intersection turning movement data collection and the people who collect this data will be the primary users of E2667, while the beneficiaries of it will be decision makers who use the data to make intersection improvements and ultimately the public.


Technical Information: David P. Albright, Bernalillo County Public Works Division, Albuquerque, N.M.

Phone: 505-848-1516

ASTM Staff: Daniel Smith

Phone: 610-832-9727