40: 40: 20
In her book Carsick, Lyn Sloman cites research from around the world that shows that car journeys generally follow the rule of 40:40:20.
40% of the car trips made by the average person could have been made by bike, foot or public transport without the need for any changes to existing bus services, cycle tracks or streets.
40% of trips are too far to walk, too difficult to cycle, or do not have a bus or train service. These trips could be made without using a car if such options were improved. Meantime, they would need to be made by taxi or hiring a car.
20% of journeys have to be made by car: typically for uses such as carrying a heavy load or transporting an elderly relative. Again, taxis or car hire would provide an alternative to owning your own car for such trips.
And the 40/40/20 rule applies to only 70% of the total trips that people make – because 30% of total trips in the towns surveyed were already being made on foot, by bike, or using pubic transport. So the proportion of trips for which a car is necessary is a lot smaller than often thought. If your journeys follow the 40/40/20 rule, how many could you make by taking a taxi, hiring a car when you need one, or by joining a car club?
Source: Lyn Sloman, Carsick, Green Books, Dartington, 2006