Yes it works with a five lane that as the op pointed out easy as it will not limit traffic in any way, however in the Netherlands, Belgium, and Germany it is much more common that children cycle to school, that people go for a quick shop on a bike and so on. All little things that add up in causes of traffic jams, and if imported to the uk also will on the slightly longer term save money on the Nhs.(because of the health benefits of regular cycling)
However Government, counties and councils have to do a lot more and in much more different ways than they do now. If i look around me for example now, there are two cyclepaths i can think of that are good, but in order to reach those i have to go to mud path first and once i'm on that path on the end it leave on needing to merge on a busy lane.(having to cross it first) If i want to cycle to London from here i can but i have to merge on to several A-roads. If i want to drive to Rotterdam from the city i was born in i could do that like i did years ago when i was 14 without having to merge on any A road because the whole route has a multiple dedicated cycle paths. It's not that the Netherlands, Belgium or Germany don't have any traffic jams at all sure they are there, but again comparing with the town i was born in, which is about the same size as the town i live in now there is a huge difference in terms of that there is much more built up traffic here.