I use the the lights and stop signs as a way to get myself to push harder to make the greens and to practice sprinting away when the reds turn green. I always feel I get a much better work out riding home my 22 miles than taking a 30-40 miles ride on the weekend.

I have never counted, but there are a lot in the first half of my ride, and very few in the second half since it is on a MUP.