What goes on a highway sign? And what doesn’t?

I sometimes wonder when driving on the interstate – assuming I’m not zoning out in commuter-mode – who decides what gets put on which signs highway signs. Why does this one mention Milford and that one doesn’t? Why is this thing mentioned on a brown sign but that thing mentioned on a green sign? Why doesn’t anybody put up signs alerting me to good Indian restaurants?

I got to answer some of those questions in a story in today’s Monitor, about changes made to one of those signs on I-93 in Concord.

I forgot to ask about Indian restaurants, though.