30 yards a second at 60mph. Doesn't take more than a couple of lorries to cause a rolling roadblock, so 10 could easily start causing chaos. And accidents. Y

30 yards a second at 60mph. Doesn't take more than a couple of lorries to cause a rolling roadblock, so 10 could easily start causing chaos. And accidents. You don't expect anyone to stop on the slip road, unless you see gridlock.