In reply to james1978:
Yes you can use them out of hours. You *should* use them out of hours.
I was told during my driving lessons that not using the bus lane when it's available would be recorded as a fault on a driving test. Effectively, you're driving in Lane 2.
Round here, they're known as Rich's private lane, as so few people seem to use them.
I suppose, since the new fines for lane-hogging came in, you could be done for not using a bus lane. Never seen it happen though, and I suspect that's not what the legislation was designed for.