Mini Master Highlights

2. What Traffic Data Are

Traffic data are measurements of the movements and behavior of people, vehicles, bicycles, and goods on transportation networks. Traffic data can be used as a performance measure to describe how people, goods, and vehicles move, where and when congestion occurs, how fast and how many users travel, and other characteristics useful for planning, design, operations, safety analysis, and research. Traffic data are often collected via both roadway and roadside based sensors, vehicle or traveler navigation and communication devices, and surveys. Some of the common types of traffic data are listed below.

Behavior

Trip rates, trip start and end times, trip modes, trip purposes, and vehicle occupancy. These parameters are often gathered from household surveys.

Count/Volume

Number of vehicles, bikes, pedestrians, tons and value of goods passing a point or segment of highway per unit time (e.g., vehicles/hour). For example, the annual average daily traffic (AADT) is a common traffic volume metric.

Classification

Vehicle types (car, truck, bus, motorcycle…), motorized vs micromobility, passenger vs. freight. FHWA 13 motorized vehicle classification is a national adopted system for traffic monitoring, planning, design, and operations.

Free Flow Speed (FFS) 

Vehicle speeds on a roadway under low traffic conditions with unconstrained interactions with other vehicles and prevailing environmental and traffic control conditions.

Incident and Event data

Crashes, roadwork, weather, and special events that affect volume and class flow.

Level of Service (LOS)

A quantitative stratification of a performance measure or measures representing quality of service. Ranging from A (best) to F (worst), these ratings are defined by the criteria established in the Highway Capacity Manual (HCM), published by the Transportation Research Board (TRB).

Origin–Destination (O–D)

Trip start and end locations, often summarized as O–D matrices. O-D traffic data are often presented in a square matrix form.

Probe Vehicle

A probe vehicle is a vehicle equipped with sensors or communication devices that collect real-time data on traffic conditions, speeds, and other roadway information as it moves through the transportation network.

Queue Length

Number of vehicles waiting (queue), length of roadway occupied, or proportion of time a sensor detects vehicle presence.

Signal Timing / Phase Data

Traffic signal states and timing plans.

Speed

Average, spot, instantaneous, and percentile speeds of vehicles. Vehicle speeds such as passenger vehicles and freight vehicles are often reported separately. 

Trajectory

Time-stamped GPS or cellular traces showing exact paths and timestamps of travelers.

Travel Time / Delay

Time taken to travel between two points and any additional time taken to travel relative to free flow conditions.

Travel Time Reliability

The consistency or predictability of travel times experienced by travelers on a particular route or transportation system over a period.

Vehicle Hours Traveled (VHT) 

The total number of hours traveled by motor vehicles in a region or corridor, over a certain period of time, usually over a year. 

Vehicle Miles Traveled (VMT)

The total miles traveled by motor vehicles in a region or corridor, over a certain period of time, usually over a year. 

Weight

Vehicle weights and vehicle axle weights are often measured through the weigh-in-motion devices.