In message , at 13:11:03 on Sat, 17 Sep
2016, tim... remarked:
It would be a nightmare of weaving cars as people who wanted
to/didn't want to pay cash realised they were in the wrong lane

None of this was a problem when the choice was Dart-tag or cash.

that's because there were no special lanes for dart tag

you just drove though a normal booth and the barrier opened without
you paying

You could do that today using ANPR for those regular users with an
account.

1) you'd still need the barrier so that it could remain closed until
the cash payer had paid the correct amount (and in the completely idiot
proof system - received their change)

No physical barrier required, just traffic lights.

2) how do you determine which punters in the queue are going to post
pay by internet?

By concluding that all those who didn't pay, and didn't have a prepay
account, must be post-pay. Exactly the same as today (apart from the
cash/card payers).
--
Roland Perry