Oyster PAYG - 2 red lights but I get to go through.

[CheapAndNerdy]

Not a dispute as it all turned out OK, but a mildly interesting incident.

At Whitechapel this afternoon, just after another passenger had passed through the gates and the light turned amber, I tapped and got a red. So I paused until amber and tapped again. Another red light with a "card already used" message. At that point a member of staff said "gate's open sir, you can go through", which it was and which I did.

During my journey I was just a teensy bit concerned at what had happened as I always make a point of checking for the green light, but at the exit station I tapped out and the correct fare was displayed.

Based on the message I presume the first red light was in error. Although if the system thought I was trying the "pass back" trick it would have slammed the gates shut at the second attempt.

 

[bb21]

Are you sure the first red wasn't because the gates read your card twice in quick succession?

 

[causton]

Would it have slammed the gates shut if it detected a passback?

If it had read your card correctly at the first attempt, it would have opened the gates.
It could then have read your card a second time, showing the first red light. But because the sensors haven't seen anyone come through from the first attempt, they would have kept it open. I believe gates can be operated where person 1 is walking through as person 2 is inserting their ticket/touching their Oyster, therefore if someone behind you had an invalid ticket the gates could start to shut on you if you are just in front of them!

So it could have kept the gates open, then the two red lights are because the gate has already been opened by a successful touch which you might have not seen because it immediately tried to read the card again.

Maybe.

 

[CheapAndNerdy]

Just checked my usage history online and there's nothing unusual.

I didn't notice any message at the first red, but that was probably because I wasn't expecting it. I was more alert for the second touch. I didn't attempt to step through the gates until I received the instruction from the member of staff.

Maybe, as has been suggested, the system did a quick double read for some reason and so the first red masked the green. I had the card in my hand and nothing else so the reader couldn't have picked up a stray signal from another card. I couldn't say at what point the gate opened (or even if it simply remained open from the previous passenger) as I was staring at the LEDs.