I never cease to be amazed at the number of clever people who believe the cost of a trip by car amounts solely to that of the petrol or diesel they buy as they refuel on the way home. From watercoolers to social media, I keep being drawn into conversations where I seem to be the only one realising that fuel accounts for only a minority of the journey’s cost to the motorist – let alone wider society. This also means I’m usually the only one realising that it’s much cheaper to use public transport. The usual whinge – “trains…