When heading Southbound on Rt. 355 you will cross the railroad tracks going over the bridge.(this is if you are going toward Old Town Gaithersburg) As you decend the hill police officers are always on the right hand side next too a large white sign. It’s cheap because you’re decending a hill and a 6 lane divided high way and yet the speedlimit is 30 mph. People have been getting tagged there for years, and I know of people being tagged multiple times in days. Also of note, the Gaithersburg Police station is across the street from this spot, hence why they are always watching it. End of the month seems to generally be the most busy.