In message , at 12:42:16 on Mon, 5 Nov
2012, tim..... remarked:
Especially if they continue to make it free between 22:00 and 06:00.
How will someone know if they have snuck into the free period and
thus don't have to phone up to pay, or just missed it by a couple of
seconds and do?

They could send that hat round for an illuminated sign informing road
users of the situation.

There's still the possibility of the sign changing the instant that you
pass it.

What happens now if you turn up at the toll booth one second before the
deadline?
--
Roland Perry