Mind the Gap

The DLR is completely step free but apparently not completely gap free - steps being vertical and gaps horizontal. I haven't worked out why some stations have the message and others don't as it doesn't seem obviously related to platform curvature (the usual reason for gaps) - e.g. Island Gardens can only be very slightly curved if it is at all.

Yes, I first heard them within the past fortnight.

Well the TfL step-free tube guide now indicates that some DLR stations have a B rated gap, unlike before. I'm not sure what drove the change, because obviously the stock hasn't changed since the last issue. What confused me more, however, is that the affected stations are still shown as step free to train on the standard map, whereas stations such as Heathrow Terminal 5 who have a B-rated gap and negligible step are not, and remain shown as step free to platform.
Stations including Greenwich, Canary Wharf, Bank and Island Gardens have changed, but the first three have straight platforms. I'm sure the gaps are not more than 85mm (threshold for a B rating).
What has driven this change, and why has it changed now? Were the gaps measured differently or classified differently before? Should a station with a B-rated gap be shown as step free to train, and if so, why aren't all B gaps with negligible step (green) shown as step-free to train?
Here's the step free guide.

Note to quiz players: expect Canary Wharf to appear in the near to mid future.

I may have mentioned this before, but some years ago I 'complained' to LU that there was always a 'temporary' sign at Shepherd's Bush H&C (as was), saying to beware of the slippery floor, and pointing out that if, after it rained, someone fell on the floor because it was slippery, they would have no defence that they had warned people, because the warning would be considered void. I've no idea if it was my mentioning it, but the sign had been there for several years, and disappeared soon after.

In fact, the floor at this station isn't particularly slippery, even when it is wet.

I noticed tonight whilst alighting from a cl508 at Hall Road on the MerseyRail network that there was no gap at all.

There was a step, but the train overhung the platform edge; if you were to measure the gap you would need to report a negative figure.

IIRC the Merseyrail 507/8s have significantly larger 'doorsteps' protruding below the passenger doors than anything that I've seen operating in the London area. As rincew1nd notes, the net effect is that the train effectively overhangs the platform.

Interestingly, looking at the pictures on the Wikipedia Page on Class 508, the 'doorsteps' are noticeably larger when in service with Merseyrail than with other operators.

Given the above I kept my eyes peeled when out an about today. It seemed (generally) that the Northern Line trains over-hung the platform edge, whereas the Wirral Line ones didn't. If it hadn't been for the step then there would be a considerable gap on the Wirral Line. As the stock is now just a common pool, the logical conclusion is that the Mersey Railway was built to a different loading gauge to the Lancashire & Yorkshire.

I also noticed that the step by the cab doors was shorter so thus didn't really overhang. I also remembered that Voyagers also have similar ankle-slashing steps.

Something that I’ve not seen mentioned here yet (surprisingly!) is that fact that these new announcements only feature on the B07 units, and not on the B90s/B2ks/B92s. And i must agree with one point that has already been raised here - the gap at every DLR station is neglegable, and personally I feel that the announcements are going down the route of “verbal diarrhoea” as they are too unnecessary...