North of 14th Street the city is almost entirely on a grid (Broadway runs diagonal and there are a couple of other exceptions). This has, at least from my observations, had three distinct advantages:
1. Building subways has been relatively easy (a lot were built by digging long straight tunnels and building the avenue over them);
2. Almost all streets are one-way, which greatly simplifies lights. A lot of cities have gone away from one-way streets because it "confuses" drivers despite it being clearly better; and
3. The lights are synchronized.
Now not all city's have NYC's regularity but the Manhattan grid has to go down as one of the greatest forethoughts in urban planning ever (IMHO).
Anyway, it's interesting to see this work so well in cities that are less regular.