As the number of private cars has increased, so too has the level of pollution in many cities. What can be done to tackle this increasingly common problem?
主体段 1：可采取的措施 1
主体段 2：可采取的措施 2
背景介绍：As the number of private cars has increased, so has the level of pollution. Overreliance on cars at the expense of public transport has made this problem even worse.
话题介绍：So many concerned citizens to look for a solution to the problem.
主题句：One potential solution to this problem is to discourage the use of private cars by raising taxes.
举例论证： If the cost of petrol was increased, then many people would consider using alternative forms of transport or even walking. Admittedly, there would be a number of complaints from car drivers, but these would not be of much importance when balanced against the environmental benefits. Modern cars are fitted with cleaner burning engines and catalytic converters. Accordingly, they do not cause as much of an environmental hazard as some older cars. In Japan, for example, cars are heavily taxed once they have been on the road for three years or more, encouraging people to buy new cars which pollute less. By heavily taxing older vehicles from the road, some of the worst-polluting vehicles would be taken off the road. However, this would not really be fair to those who cannot afford a new car with such regularity.
主题句：An improvement in the quality and efficiency of public transport would also encourage people to use their cars less.
举例论证： In London, for example, a system has been operating for some time in which people are allocated days of the week when they can use their cars. On days that they are not allowed to drive, public transport is taken.
Although these are potential solutions to the problem, none of them are perfect. Only by a concerted effort by both the government and the public can this situation truly be resolved.
a number of 一些
take off 出发;动身