Driving back from Buxton, I followed a car for a number of miles. The driver was one of those people who make anticipation more difficult. Usually it is easy enough to follow another car safely and without effort, but some drivers don't drive in a conveniently predictable way.
They slow down to an excessively cautious crawl going round a bend and don't speed up as much as one might expect coming out of the bend. Then they go round the next bend at a more typical speed and speed up out of the bend too.
In my experience, mildly erratic and unpredictable drivers are often talking to a passenger. I assume the cadences of their driving match the cadences of the conversation.
A hand waves expressively and the brake lights flick on and off. As if the driver is slowing slightly in order to add a touch more concentration to the conversation.
Then it's the passenger's turn to speak and the car speeds up again. Or the car travels quite predictably for a mile or so, as if the conversation has lapsed.
Finally the car on the Buxton road stopped at a junction. I could see the driver nattering away like crazy, as if using this brief stoppage to get in as much talk as possible.