Good question. I moved there after all this has happened so can’t judge either way. Feel free to tell me I’m chatting shit but this did happen in Leyton where I was previously residing and yes there was a noticeable difference there.
Despite what some people say, it's not inevitably true that LTNs increase traffic on boundary roads or nearby main roads.
It's also not possible to say that they never have some effect on boundary roads. It is true that increases in traffic are often seen, on boundary roads, after the implementation of LTN type schemes. However:
1. An increase immediately after implementation is normal. Also normal is for things to settle back to something like the previous level after a period of time. That period of time seems to range from a couple of months to a couple of years
2. It's pretty hard to untangle the effects of an LTN implementation from all the other things that might be having an effect at a certain time. Again, longer term observations are the more important
3. There's a tendency to notice congestion and pollution more, once you've started looking for it. It seems like a lot of people who never thought that much about air pollution, are now hyper vigilant.
4. The LTNs are part of a whole bunch of measures being pushed out around London aimed at reducing private vehicle use. Aside from any effects the LTNs are having, there is, hopefully, a general background decrease in air pollution and vehicle use.
5. Those of us who are generally in favour of these things have to be honest, I think, and acknowledge that yes, there will be
some places where traffic levels increase on boundary roads. Pinch points get shifted around, so even if the overall level of traffic in an area goes down, there might be a few places where it goes up. However, nothing can ever be perfect and as long as these increases are not widespread and are not extreme, the overall benefits mean they should be accepted. Also, where these increases happen, action should be taken to mitigate them, but the mitigation should not be to abandon the whole scheme or compromise it so much that the benefits become really marginal.
For the record where I live isn't in an LTN and never will be, it's not a very major road but it's a sufficiently main road that I don't expect it would ever be closed off and it's one that could be subject to worries about displaced traffic if an LTN was implemented either side of it.