Viewed from a scientist's standpoint,all of the energy contained in fuel either now or in the future becomes heat.Some of the heat is used directly or produces useful work.The rest is lost or rejected.That is to say,it is radiated into the atmosphere from the engines,motors,furnaces,power lines,television sets,boilers and all the other energy-consuming machinery that makes our wheels go around.
It is necessary to improve the efficiency with.which we use energy in order to do more work.But improvement cannot come overnight,and there are limits beyond which not even science can help.According to the Center for Strategic and International studies,about three quarters of the energy we use to move things,including ourselves,accomplishes no useful work.
In terms of efficiency,buses,trains,and other forms of public transportation may be using en-ergy more efficiently than private automobiles.Unless private automobiles can operate at near capacity,their overall efficiency is poor.For example,an urban bus carrying 36 passengers may achieve an efficiency of around 120 passenger-miles per gallon of gasoline.But buses are not al-ways fully loaded,and sometimes they carry no passengers at all.
It is true that buses can sometimes run without passengers.City trains seem to be very effi-cient,but they suffer the same shortcomings as buses and cost more.Except for rush hours,com-muter trains seldom run at full capacity.This wastes even more energy and is more than the management can afford.As a result,commuter trains are truly practical only in places where there are a lot of people.
For some people,mass transportation may serve their needs.For others,a combination of mass transportation and private transportation may be preferable.Better design and wise use of both mass transportation systems and private vehicles will play an important part in helping us make full-er use of energy for transportation.
Now match each of the persons to the appropriate statement.
Note:there are two extra statements.
A.City trains and buses have different faults to overcome.
B.The efficiency of the city train depends on the size of population.
C.Public transportation is usually more energy-efficient.
D.Private cars usually run at full capacity.
E.No fuel energy is fully used.
F.A combined means of transport can help increase energy efficiency.
G.Problems of energy loss can never be completely solved.