It's not unheard of for street lighting circuits to have a rather unique transformer / wiring arrangement as part of the way to deal with voltage drop and damaged lights.
I really would not attempt to change the lighting circuit, in any way, unless I was absolutely certain as to how the circuit was wired. It goes beyond anything as simple as taking reading from your meter.
Otherwise ... and here you know the site, and I don't .... I'd consider planning for more power in the future. I can see there being a vending machine, a heater, and even a snack bar added at some future date.
