and a regular car have effective frontal areas of about 0.8 m2 and 0.5 m2 re-
spectively, a full commuter train from Cambridge to London has a frontal
area per passenger of 0.02 m2.

But whoops, now we’ve broached an ugly topic – the prospect of sharing
a vehicle with “all those horrible people.” Well, squish aboard, and
let’s ask: How much could consumption be reduced by a switch from
personal gas-guzzlers to excellent integrated public transport?

Public transport

At its best, shared public transport is far more energy-efficient than indi-
vidual car-driving. A diesel-powered coach, carrying 49 passengers and
doing 10 miles per gallon at 65 miles per hour, uses 6 kWh per 100 p-km
13 times better than the single-person car. Vancouver’s trolleybuses con-
sume 270 kWh perE vehicle-km, and have an average speed of 15 km/h. If
the trolleybus has 40 passengers on board, then its passenger transport
cost is 7 kWh per 100 p-km. The Vancouver SeaBus has a transport cost
of 83 kWh per vehicle-km at a speed of 13.5 km/h. It can seat 400 people,
so its passenger transport cost when full is 21 kWh per 100 p-km. London
underground trains, at peak times, use 4.4 kWh per 100 p-km – 18 times
better than individual cars. Even high-speed trains, which violate two of
our energy-saving principles by going twice as fast as the car and weighing
a lot, are much more energy efficient: if the electric high-speed train

Figure 20.5. Some public transports, and their energy-efficiencies, when on best behaviour. Tubes, outer and inner. Two high-speed trains. The electric one uses 3 kWh per 100 seat-km; the diesel, 9 kWh. Trolleybuses in San Francisco. Vancouver SeaBus. Photo by Larry.