Coming down from a Christmas in London on 27th the motorways were crowded. It was almost impossible to go at 70 mph (the national speed limit) anywhere between London and Bristol (roughly100 miles) and then the problems continued well past Taunton, added to which it rained.
There was only one accident that we passed so the low movement was all congestion. All of us moving between homes on the same day. And that is just cars.
Imagine what will happen when hundreds of millions of people start moving just trying to find a home.