The Oyster Card readers at London City station are in a ludicrous position and there have been innumerable complaints and comments about them. They are at the bottom of the escalators hidden behind a pillar facing in the opposite direction to people coming in (so they face those coming out). Eventually an additional one was provided, but in an even more obscure location.

If your only previous experience of the DLR was going out on it from Tower Gateway station TO the airport, you will know that the entry readers are at the top of the escalator, as you enter the platform. Whereas at the airport they are at the bottom of the escalator, not obvious, and there is nothing at the top at all.

Now the technical bit. When the readers were installed, the driving force behind where to site them was convenience of an electrical supply to them. Nothing to do with what makes them obvious. So if the electrician found the current position for them the easiest for wiring them up, that is where they went.

Of course, if they had been installing a London Transport special sign to show they were having a Good Service today (displayed permanently whether true or not), there would be no budgetary restrictions at all to mounting it in the most prominent position on the station as possible, with whatever electrical work might be needed to floodlight it elegantly.

The conductors on the DLR trains who are meant to check all tickets as you go along (yes, on a six coach train in the rush hour with no throughout corridor !) actually are a reasonable bunch and are well aware of the shortfall at LCY station (and some others), and they are good at sizing up those confused agains real fare-dodgers, and will just ask you to get out and touch in. This doesn't apply to the periodic ticket inspection "snatch squads", for whom duty on the LCY line must be Corn from Egypt for the number of fines they can write out. By the way, the regular train conductors hate these people.