Urban Transport Strategy. Management in Developing Countries John A Cracknell, страница 76

9.1         Introduction

9.1.1.      Chapter 2 has outlined the trend that as city populations and economies grow and as car ownership and use increase, the likelihood is for worsening urban traffic congestion. While all cities need a well developed road network, road construction-capacity, even if it was affordable, will not be able to keep pace with growth in travel demand; furthermore, new roads generate traffic.  Policies are needed to deal with inevitable increasing urban traffic congestion.  Increasing traffic congestion may inhibit traffic growth in urban areas but (i) drivers have shown themselves to be extremely resilient to congestion and (ii) congestion is economically inefficient and environmentally damaging as a method of dealing with excess traffic demand.

9.2         Rationale for demand management^[35]

9.2.1.      The effects of traffic congestion include (i) economic disbenefits arising from loss of time, increased vehicle operating costs, etc (ii) congested traffic produces more pollution per vehicle kilometre than smoothly flowing traffic (iii) congestion prevents bus and other road based public transport operators from providing a reasonable level of service, (iv) city centre congestion encourages dispersal of journeys to outlying city areas where current congestion is lower but to where it is likely to spread.  The basic economic rationale for demand management is that unless the price directly incurred by travellers in making journeys covers the full costs of the journey, their travel will impose a net cost on the community.  The full costs of road use by car includes both the personal costs which the traveller incurs (vehicle running costs, fuel, parking etc) and the social costs which the traveller imposes on the community, through adding to congestion and increasing the potential for accidents, as well as the adverse impacts on the environment, through creating noise, atmospheric pollution and contributing to severance.  As the marginal costs imposed by a road user on others vary by location, time and traffic conditions so, ideally the charges incurred by road users should also vary.  In developed cities, the argument for managing travel demand has, however, broadened beyond that based on economic efficiency.  This reflects increasing concern about the environmental and social impacts of congestion on urban communities and the need to seek sustainable cities.  Although the construction of additional or alternative road capacity can alleviate some of the effects of congestion, the benefits are most likely to be offset, unless growth in traffic volumes is restrained.  Limitation on funds available for investment in urban transport has also contributed to the debate about the extent to which (i) users should pay full costs of the provision of the road system and (ii) demand should be restrained to match the supply (of roads) which can be provided.

9.2.2.      Based on this rationale, the objectives of urban traffic demand management policy are:

a)  to reduce traffic congestion; and

b)  to reduce adverse traffic related impacts on the city environment.

9.3          Demand management measures

9.3.1.      All demand management tools aim to increase the costs of road use either explicitly through charges (parking or congestion charges or fuel prices) or implicitly (through limitations to movement) such that road user costs more closely approach full costs of travel.  Demand management and restraint in traffic volumes may be realised by a range of measures, many of them well beyond the concept of "traffic management" and often dealing with national policy (e.g. fuel pricing).  Potential demand management measures may be divided into the following categories:

a)  Parking - controls and pricing of public car parking and of other parking such as private non residential parking;