Reversible lane deployment in Roswell, Georgia has improved capacity in the peak direction, though higher collision rates have been observed along the reversible corridor.
The benefits of reversible lanes in Roswell are emphasized when congestion is worse when the reversible lane system is not operational due to routine maintenance during peak periods.

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.

Reversible Lane Deployment

Roswell, GA has used reversible lanes on a 1-mile corridor of South Atlanta Street (State Route 9) between Marietta Highway to Riverside Road for over 30 years. This corridor is configured as a three-lane facility with a reversible center lane. State Route 9 and US-19 are the major routes crossing the Chattahoochee River connecting the northern Atlanta communities with downtown Atlanta. The State Route 9 corridor is mainly a four-lane arterial facility, except the reversible lane corridor. A number of historic places along the road made it difficult to widen the road to four lanes, so a reversible lane was implemented instead.

Reversible lanes are implemented here with overhead illuminated signs. There is a sign above each lane with the outside lanes showing a static arrow so drivers know it is always available for the direction they are traveling. The center reversible lane shows a red X or a green arrow, depending on the time of day and which direction is using the reversible lane. This corridor operates its reversible lanes in three different patterns.

  • 1 a.m. to 5 a.m. the corridor maintains one lane in each direction, the reversible lane is closed in both directions.
  • 6 a.m. to 11 a.m. the corridor maintains two lanes in the southbound direction toward Atlanta.
  • At all other times of the day, the corridor maintains two northbound travel lanes.

When the reversible lane changes direction, the system closes the reversible lane for all directions of travel. After a 5 minute clearance interval, the system reopens the lane for the reverse direction.

Additionally, the northbound approach to the segment has two signs. The first sign warns that the lane ends in 1,000 feet, and the second warns the lane ends in 250 feet. These are blank when there is not a lane drop but illuminated when there is. The southbound approach has one sign warning of a lane drop but no reference to distance.


  • Improvement to capacity in the peak direction. The reversible lane adds capacity for the direction it is operating in and the city experiences major backups when the reversible lane system is down for repair.
  • Higher collision rates along the reversible lane section of SR-9. This section has a lot of horizontal curvature in addition to the reversible lanes, and it was found that collision rates were higher than for similar facilities without reversible lanes.
Goal Areas
Results Type
Deployment Locations