It would have to be an enclosed area, in Putney they have cycle lanes on the pavement, but because it's just marked on, people just wonder on to them. But if there was something to separate it (like a kerb on both sides, for example) perhaps (but not necessarily) ppl would take more notice.
In Islington there's a tiny bit of road where the cycle lane is actually separate from the road and the pavement, and that would be ideal, but I can't see the gvmt investing on this, even though it wouldn't cost that much to raise kerbs on the road, between the main rd and pavement.