Lane Merge Systems

Late last year the FHWA Every Day Counts initiative held another wonderful webinar. This one covered two more work zone ITS products: variable speed limit systems and dynamic lane merge systems. You can view the recorded webinar at:

Last time we discussed portable variable speed limit systems. Today let’s discuss lane merge systems. Todd Peterson of FHWA began by explaining the basic structure and goals of a lane merge system and explained the differences between a late merge, early merge, and dynamic merge system.

Chris Brookes described Michigan DOT’s use of a late merge system. Their applications were last minute, high volume so a late merge made sense. He shared data showing remarkable reductions in queue length and delays. But he said there is a “steep learning curve.” When the local media supported their efforts with stories on the system, remarkable benefits were achieved. But when they did not run stories, those benefits disappeared. So drivers need to understand how the system works, what is expected of them, and why that will benefit everyone concerned.

Todd Peterson described a dynamic merge system in Maryland. There they saw high volumes during the day and low ones at night. So an adaptive system made more sense for them.

In both Michigan and Maryland they enjoyed several benefits as a result of these systems:
• Reduced speed differential between two open lanes in advance of the closure – Michigan had no recorded crashes when the system was in use.
• Reduced frustration by creating a sense of fairness.
• Reduced queue lengths – Michigan saw them go from 5 to 7 miles down to less than 2.
• Reduced delays – Maryland saw increased throughput of 9 to as much as 34%.

During this presentation two more questions were asked of the audience. They asked if their agency was considering using lane merge systems and about 70% of them are. They then asked if they were looking at early merge or late merge. 100% were considering late merge. There is no data to support this, but you’d have to suspect the interest is coming from agencies working in urban areas with high volumes and resulting capacity issues.

The data presented clearly shows remarkable benefits from late merge systems. Their low cost and ease of deployment make these an excellent tool. The Every Day Counts website includes lots of useful resources to help your agency get started using these systems. Check it out at .

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