Deployment of Bluetooth devices to collect arterial travel time data in Cobb County, Georgia helped with signal timing project evaluation and monitoring real-time traffic conditions.
The device vendor provides county staff with a continuously updated color-coded map for real-time updates and enables the county to push important travel information to the public.


Cobb County
United States

NCHRP Synthesis 447: Active Traffic Management for Arterials

Summary Information

This synthesis documents the state of the practice associated with designing, implementing, and operating active traffic management (ATM) on arterials. Information for this synthesis was gathered through a literature review of advanced ATM methods for arterials and in-depth telephone interviews of agencies selected through a screening interview. The study has provided information on strategies used to actively manage traffic and congestion on arterials; situations and operating conditions in which ATM strategies have been successfully and unsuccessfully deployed on arterials; and system and technology requirements associated with implementing the strategies.

Collection of Arterial Travel Time Data with Bluetooth Devices

Cobb County, Georgia has 19 Bluetooth devices collecting arterial travel time data on three corridors ranging in length from 2 to 6 miles long. Device-equipped and internet-connected signal controllers on this corridor send data back to Bluetooth vendor. The Bluetooth vendor hosts a web page with a map that county staff use to see congestion levels on these corridors. The map uses a green, yellow, and red color scheme to report congestion levels. There is also a blue color code designating areas where travel times indicate the speed limit is being exceeded. The county can send information to the public and is currently using this feature on its website. The project was funded by the Georgia DOT and deployed as a pilot project for the state.

Accuracy of the travel time data collected by Bluetooth devices is gauged by performing car travel time surveys on the corridor. The results have been similar between the travel time surveys and data from the Bluetooth devices.


Evaluation. The Bluetooth data enables Cobb County to do before and after analyses of signal retiming projects.

Real-time traffic condition information. This information enables the county to see and resolve issues more quickly. The data is also sent to the 911 operations center, which can monitor traffic and locate potential incident locations more quickly.