Nick Ludlam, who took the picture, felt we needed more look up tables. Would you like to see more signs like this across the network? Considering there are around 100 error code messages including the cryptic "82 - Illogical use of ticket" , "33 - Illogical interchange through gates" and "55 - Possible Dumbbell", the Tube would need a very large whiteboard to list them all!
However, there's certainly something to be said in knowing what the most common ones mean.
Also does anyone know how many of these error codes still let people through the gates - even if they cause the barriers to double beep? It's all very well seeing a code (and knowing what it means if you can't get out", but what's the point of a code if you can still get through the gates.
I'm often behind people going through gates which beep twice and flash "Seek assistance" and I've hardly seen anyone return back to see what the problem is. I don't use PrePay as I have an annual Oyster Card, but if the double beep meant I was going to be charged more than I should be paying, I'd certainly pay attention to the codes & beeps.