Many towns and cities in developing countries are experiencing acute traffic congestion problems brought about chiefly by the growth in the number of motor cars. One method of easing the problem, which has been used in Bangkok for a number of years, is to ban the movements of lorries in the urban area during peak periods. For 6-wheel lorries, the ban lasts for four hours per day and for 10-wheel lorries, lasts for ten hours. This report describes a study of the effects of the bans. By dividing the urban network into different regions, considering different periods of the day separately, and applying empirical speed flow relationships, estimates are made of the effects of the bans on travel times and costs of other road users. It is concluded that each ban reduces the travel costs to other road users by close to one per cent ( 3M- 4M per annum at 1980 prices, excluding tax); that for the ban on 6-wheel lorries, reductions in congestion costs probably exceed increases in costs to goods vehicle operators; but that for the ban on 10-wheel lorries, costs and benefits are more evenly balanced. Reducing the duration of the ban on 10-wheel lorries would increase its cost-effectiveness. (A)

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