Are box junction fines fair in busy areas?

I feel these motorists pain.

http://www.bbc.co.uk/news/uk-21023615

While I try to be a good motorist and stay out of box junctions I have been caught in one and fined. The problem is in an ideal world they work and you can abide by their rules. But in congested London traffic you either get someone cutting in forcing you into the zone or you sit there for days waiting for a gap while everyone else cuts you over. Then there is the driver who decides to stop dead with amble space in front of him just to get you! When traffic flow is one car at a time they are increasingly impractical and very difficult to judge when it’s good to go. It’s all too easy to end up in the box with a fine in your lap.

The council knows this of course which is why it loves to camera them. I say give all the revenue (less admin) to charities. Then we will see how much the camera is aiding traffic flow and not filling coffers.

I would also like to know the legalities of box cameras. Bus and Speed cameras have warning signs. Box cameras do not. I say it’s unfair to impose a fine where the driver does not have practical chance to obay the law.