I was living in America when they started to use these.

the general Freeway flow DOES inmprove.... but its normally at the cost of time acctaully getting to the freeway.

With lights at the freeway onramps traffic can bank up pretty good if you dont have enough lanes for the onramp.

Overall you dont acctaully get anywhere any faster.... and if you do it is very marginal. Waste of money imo