Often wondered why street lights on all night. Wasted energy etc. Also
unnecessary pollution where electrcity is generated by coal or other
fossil fuel. Could save some small municipalities some cost?

Apparently a German town/city has decided to turn them off.

However provision is made for residents to call a telephone code that
will switch them on for a timed period in their area. The call can be
made from a home phone or from a mobile/cell phone etc.

So it would appear that a householder could turn them on; as could
someone making a late night delivery, a taxi driver looking for
certain street etc.