is full, its energy cost is 3 kWh per 100 p-km – that’s 27 times smaller than
the car’s!

However, we must be realistic in our planning. Some trains, coaches,
and buses are not full (figure 20.6). So the average energy cost of pub-
lic transport is bigger than the best-case figures just mentioned. What’s
the average energy-consumption of public transport systems, and what’s a
realistic appraisal of how good they could be?

In 2006–7, the total energy cost of all London’s underground trains,
including lighting, lifts, depots, and workshops, was 15 kWh per 100 p-km
– five times better than our baseline car. In 2006–7 the energy cost
of all London buses was 32 kWh per 100 p-km. Energy cost is not the
only thing that matters, of course. Passengers care about speed: and the
underground trains delivered higher speeds (an average of 33 km/h) than
buses (18 km/h). Managers care about financial costs: the staff costs, per
passenger-km, of underground trains are less than those of buses.

The total energy consumption of the Croydon Tramlink system (figure
20.7) in 2006–7 (including the tram depot and facilities at tram-stops)
was 9 kWh per 100 p-km, with an average speed of 25 km/h.

How good could public transport be? Perhaps we can get a rough indication
by looking at the data from Japan in table 20.8. At 19 kWh per
100 p-km
and 6 kWh per 100 p-km, bus and rail both look promising. Rail
has the nice advantage that it can solve both of our goals – reduction in energy
consumption, and independence from fossil fuels. Buses and coaches
have obvious advantages of simplicity and flexibility, but keeping this flexibility
at the same time as getting buses and coaches to work without fossil
fuels may be a challenge.

To summarise, public transport (especially electric trains, trams, and
buses) seems a promising way to deliver passenger transportation – better
in terms of energy per passenger-km, perhaps five or ten times better than
cars. However, if people demand the flexibility of a private vehicle, what
are our other options?

Figure 20.6. Some trains aren’t full. Three men and a cello – the sole occupants of this carriage of the 10.30 high-speed train from Edinburgh to Kings Cross.
Figure 20.7. Some public transports, and their average energy consumptions. Left: Some red buses. Right: Croydon Tramlink. Photo by Stephen Parascandolo.
Energy consumption
(kWh per 100 p-km)
Car 68
Bus 19
Rail 6
Air 51
Sea 57
Table 20.8. Overall transport efficiencies of transport modes in Japan (1999).