The Democratic Party has proposed a ban on cars and trucks entering busy districts when air pollution is high. It said this would help ease the problem until medium and long-term measures came into effect. The proposal was among several in a package published by the party for consultation. Launching the campaign yesterday on the eve of World Environment Day today, some leading party members travelled by environmentally friendly means to show their support. The party's spokesman on environmental policy, Law Chi-kong, said: 'Hong Kong is a densely populated city. When the [Air Pollution Index] hits 150, it poses a health risk. In addition to measures for the medium and long term, we ought to take some urgent measures if the index reaches 150 in districts such as Central. 'In some districts, we should restrict lorries to loading and unloading their goods only between 7pm and 7am.' In its proposed package, the party also suggested giving tax incentives to drivers to use cleaner fuels.