RogerBW's Blog

Pretty much every Wednesday evening, I drive to Cambridge and back. Since I leave at about the same time, I have some fairly consistent data about traffic patterns. (Images follow.)

Here's the map of all the routes I've taken, outbound. In fact the A1(M) (via Welwyn Garden City) is the one I almost always use; all that messing about through Berkhamstead only happens when things are really slow elsewhere.

These are the home-bound routes. I diverge more: there's less of a deadline, there are more likely to be roadworks on the major route, and sometimes I divert to make a Freecycle pickup.

But I can get more information out of these data. Here, for each pixel on the map, I paint it black if my average speed while in that pixel was over 50mph and red if it was less (then expand the pixels to 3x3 squares to make them easier to see).

Obviously most of the urban areas are slow, as well as junctions, but that spot just north of Welwyn Garden City is distinctive: it's where the carriageway narrows from three to two lanes, and there's almost always a traffic jam on the outbound route.

On the way back, the cross-country experiments become much clearer, as well as the speed restrictions on the A10 (south from Royston to Buntingford and Ware), which is why I don't often use it.