Conventional wisdom tells us that public transport is more efficient than private transport. Transport executives and urban planners will rattle off data in support of this, citing, for instance, that it would take around 30 cars – with an average of two occupants per vehicle – to equal the capacity of a single-deck bus. And of course, the road space taken up by those 30 cars is much more compared to one bus. Common sense also tells us that the argument holds true.
If you do a search on the Net, you will also find many counter-arguments, with most of them citing the low occupancy rate of public buses. But these arguments hinge on national figures in fairly large countries, with a mix of rural and urban bus operations.
And averages often tell a strange tale. For instance, the average occupancy of public buses in the UK in 2005 was nine. Obviously, a full-sized bus with the capacity for 60 to 70 passengers isn’t going to be very efficient with only nine aboard. It is worse if you factor in the fuel consumption of a full-sized city bus (2.5km to 3km per litre). Against these numbers, the car makes a lot more sense.
How will the argument pan out in a highly built-up city state such as Singapore, though? If we go by persistent complaints of crowdedness by commuters, it would seem the asset utilisation of bus fleets here is much higher. Therefore, we can infer that public transport is more efficient than private cars on this sunny island.
But is it true? Based on our calculations, it is only the case during peak hours, when buses are generally operating close to full capacity. In off-peak periods, buses have an occupancy level of as low as 20 per cent.
Let us look at averages, then. According to the Land Transport Authority, the average bus trip is 4.5km (2011 data). The average number of trips a leading bus company here caters to is 2.6 million a day. Over a year, it caters to 949 million trips, and it uses 130 million to 140 million litres of diesel.
To work out the average fuel efficiency of each trip, multiply the annual trips by average trip distance (4.5km) and you will get 4.27 billion km. Divide that by 135 million litres and you will get 31.6km/L. That is efficient, if compared to the average fuel efficiency of an average car with a single occupant (10km/L, according to LTA data).
But what if you have two or more occupants per car? The equation becomes vastly different, even if you factor in an average three per cent increase in fuel consumption per additional occupant. If you have four occupants, the car effectively becomes more fuel-efficient than the bus.
If you drive a thrifty petrol-electric hybrid like the Toyota Prius, you will need only two occupants in the car to match the fuel efficiency of a bus.
But the truth is that not every car here is a Prius, and quite often, it has only one or two occupants. So, the answer to improving the fuel efficiency of driving is to either car-pool or choose a fuel-efficient model like the Prius. What about road space? Even with four people per car, we would need 17 cars to match the capacity of a single-deck bus, or around 30 cars to match the ferrying capacity of a double-decker or bendy bus.
Well, cars do not have to travel a fixed route or stick to a fixed schedule like buses, although the state of peak-hour traffic seems to suggest that they do. They can spread out over space and time. And if they do, they will contribute far less to congestion.
For cars to be able to spread out over space and time more effectively, we’d essentially require two things: flexible working hours and decentralised urban planning. Singapore currently has neither. It would take years to change the culture to facilitate the former, and decades of innovative town planning to make the latter happen.
One last thought: Can Singapore’s population of about 610,000 cars cater to the total 3.4 million bus trips that commuters make a day? With technology and a willingness to share, yes. Singapore’s car population clocks a cumulative 12.2 billion km a year – more than double the total mileage clocked by bus commuters.
It is conceivable that half of this 12.2 billion km is travelled in cars occupied by only one or two persons. With a system similar to car-sharing schemes such as Car2go, Zipcar and DriveMyCar, it is possible to match the underutilised car capacity with demand from bus commuters. But until then, buses will continue to fulfil a vital role in our land transport landscape.
This article was written by Christopher Tan, consulting editor for Torque.