The adaptive cruise control always reduces speed when approaching ipass overhead gates on the highways.

This is in the Illinois Wisconsin area. Every time we get within a few hundred feet of ipass, the car will slow down to the exact speed limit. Anyone else experience this or know why it happens?

 

That's the route-based speed adaption, and is explained in the owner's manual. You can turn it off if you don't like it.

 

Mine does that too on the I-95 Express Lanes when approaching the EZpass sensors! I think the route based speed adaption thinks it is a toll booth, vice a sensor station that doesn’t require you to slow down.

 

It is also possible that the map data is bad. I see a lot of times where the speed limit on those express lane was set the same as the toll booth (at least on here map, which provides the map used in the Mercedes) The adaptive cruise control uses both what it can see (speed limit sign) and map data to determine the travel speed limit.