When traveling from A to B it seems that people tend to prefer roads which lie south of a line joining A and B (maybe because North feels ‘uphill’).
In an attempt to redress this cognitive bias and redistribute the traffic levels on alternative routes, today’s invention involves representing such southerly roads by thinner lines on a map.
The impression given would be that these are less easily passable and thus help equalise the number of journeys via northerly and southerly routes.