I was driving down the motorway the other day when the traffic suddenly came to a standstill. After 10 slow minutes of being mostly stationary, the traffic started moving again and was back up to full speed almost immediately. There was no visible reason for the standstill, no accident or junction in sight, and it was slightly later than morning rush hour. Can anyone tell me why traffic bunches up like this for no apparent reason?
Edith Harris,London, UK