Work Zone Mobility and Safety Program
Photo collage: temporary lane closure, road marking installation, cone with mounted warning light, and drum separated work zones.
Office of Operations 21st Century Operations Using 21st Century Technologies

Best Practice


J1−4: Dynamic Lane Merge


At work zone lane closures, conventional merging practices can sometimes lead to long queues, undesired speed differentials between lanes, aggressive driving, and an increased potential for traffic crashes. A dynamic lane merge system that varies merging behavior based on traffic conditions can help smooth traffic flow approaching a merge point. A dynamic lane merge implementation involves the deployment of both static and changeable message signs, in conjunction with ITS technologies, to encourage drivers to either merge early or late (depending on traffic volume) as they approach a lane closure. Dynamic lane merges can have a positive effect on aggressive driving, queue lengths, throughput, crashes, travel time, and speed differentials between lanes, resulting in improved safety and mobility.

One example of a dynamic lane merge implementation is the Indiana lane merge system (ILMS). ILMS involves a dynamic no passing zone placed prior to the taper of a work zone. Work zone engineers place an initial sign, equipped with constantly activated flashing strobes, followed by additional signage that is automatically activated upstream of the work zone when capacity is high in order to alert drivers of the no−passing zone. The Indiana Department of Transportation (INDOT) completed a comprehensive study of the expected impacts of ILMS and how it could positively affect work zone safety and mobility in the future as a part of ILMS implementation activities.


The Indiana lane merge concept was developed to reduce aggressive merging near the taper and encourage motorists to switch lanes well upstream of the discontinuous lane taper.


Benefits realized from this lane concept are improved safety as a result of fewer crashes, and improved traffic smoothness and mobility. The study of the ILMS showed that as the number of vehicles on the roadway increased, ILMS's dynamic no−passing zone algorithms improved safety and decreased congestion. As the congestion decreased, ILMS had less of a positive effect on congestion and safety.


Freeways in urban and rural environments where congestion is expected due to lane closures.




John (Pat) McCarty, Senior Engineer, Work Zone Safety, Traffic Management Division, Indiana DOT
Phone: (317) 899−8626

Office of Operations