Merging is one of those things that really annoys me. The road planners (ha!) here have installed lights onto the on-ramps of a motorway I use. The theory is that the traffic joining is filtered so the road doesn't reach full capacity. However as the lights let out 8-10 cars each time you just end up with a line of nose-to-tail cars all in a hurry to pull out asap which of course leads to "conflict" with the cars already there.
And of course those who merge whilst not matching the speed of traffic already there.