Traffic Volume Counts

Interactive Map

About Traffic Counts

What

Why

When

Where

Who

How

Contacts/Other Resources

Traffic counts—the number of vehicles passing a given point over a given period of time—come in a number of different "flavors," which are described below.  The MPO warehouses all of these kinds of traffic counts, but only ADT is currently available through this web site.

• [Simple] volume is the total number of vehicles of all kinds in a unit of time, usually an hour.
• Peak volume is the total number of vehicles in a peak travel period, usually the commuter rush hours of 7–10 a.m. or 4–7 p.m.
• Average daily traffic (ADT) is total traffic during a period divided by the number of days in that period.  An adjustment factor may be applied to extend the result's applicability to a period longer than the measurement period. For example, ADT calculated from a week of measurements in June cannot be extended to the whole year without first adjusting for seasonal variations in traffic.
• Average weekday traffic (AWDT) is the average number of vehicles per weekday, calculated by dividing total traffic during a weekday period by the number of weekdays in that period.
• Classification counts measure different types of vehicles in a unit time, frequently a quarter hour.  Typical classes or types are motorcycles, passenger vehicles, light trucks, three-axle trucks, and so on.
• Speed counts measure the number of vehicles in different speed ranges in a unit of time.
• Turning ("turning movement") counts measure the number of vehicles making different possible turns at an intersection in a unit of time, usually a quarter hour.  The turns are described using the names of the streets involved and the directions of travel: for example, "Main Street northbound to Elm Street eastbound." Each road feeding traffic into an intersection is measured, and pedestrian crossings of this road may be included.