In Melbourne, Australia, a similar concept was used to ease congestion entering freeways. We had a peak-hour problem where cars would flood the entry ramps, but

In Melbourne, Australia, a similar concept was used to ease congestion entering freeways. We had a peak-hour problem where cars would flood the entry ramps, but struggle to merge with the existing freeway traffic - this caused people to brake/slow down which resulted in major jams. To alleviate this issue "there are traffic lights at some freeway entrances to control the flow of vehicles onto the freeway when the traffic is heavy. When operating, the lights will change quickly, so that when the light is green only one vehicle in each lane will be able to enter the freeway." (taken from VicRoads website) The lights basically cycle from red to green every 2 seconds. That's enough to regulate the flow onto the freeway and minmises jams on the entry ramp and at the merge point between the freeway and entry ramp.