Traffic Update

I had to go shopping today. It's not something I like to do, but if we want to eat it has to be done. As I left Sainsburys, having inadvertently destroyed the milk shelf - don't ask - I found myself caught in a traffic jam tailing back from roadworks on the road to the right.
Firstly I was miffed at finding myself caught in someone else's jam and secondly I was staggered by the amount of traffic out there. Some of it was obviously work traffic - builder's trucks, delivery vehicles, reps in cheap suits - but there were an awful lot of private cars out there too.
It was the middle of the morning and I had expected the roads to be fairly quiet. Where did they all come from? What were they doing? And why they heck did they all have to be going the same way as me?