Myth: Cars are more efficient because they never run empty

Myth: Cars are more efficient than public transport because they never run empty
Fact: Not every person-trip in a car is valuable. When one person drops off another and returns home, the car is equivalent to a public transport vehicle with no-one but a driver on board.

This argument occurs to many people who are disillusioned by observing some of the hopeless bus services that run around Melbourne’s suburbs. The thought is that with a timetabled public transport service, there’s always some chance that the vehicle will run empty and the trip will be wasted. But cars always have someone in them, so they have a head start in efficiency.

If one thinks a little more carefully, this isn’t really true. Even an ’empty’ public transport vehicle has a driver on board; however, the driver quite properly isn’t counted when tallying up the ‘valuable’ journeys. But what happens when a parent drives a child from home to a friend’s place and returns straight home again? There is only one ‘valuable’ journey: the child going to the friend’s place. Effectively the car is empty on the trip home, and three person-trips have been generated for the equivalent of one valuable journey! If the child had access to effective and safe public transport, those extra two trips could in principle be avoided.

As many recent commentators have pointed out, a future move toward robot cars could only exacerbate this effect – particularly if they mimic present-day cars in being owned by individual motorists, who will find it attractive to send their robot car home empty or just tell it to circle the block, rather than seek out costly car storage in the middle of the city.

Robot cars are still a way off, however. And in this world, transport surveys routinely find that the fastest-growing trip purpose is the one charmingly designated ‘Serve passenger’. In 1964, about 9 per cent of trips in Melbourne were of this type; by 1994, this had doubled to 18 per cent. Moreover, recent figures from the Victorian Government’s travel surveys indicate that 40 per cent of all school travel involves a parent travelling from home to school and returning directly home again. So this isn’t just an academic point: it has important consequences for the way we assess transport policy.

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Last Modified: 25 October 2016