Urban Transport Strategy. Management in Developing Countries John A Cracknell, страница 26

3.3.2.      As with all traffic management, specific city conditions influence heavily bus priority

policy.  In cities where traffic congestion exists and where buses play a major role, there is strong case for bus priority.  In developed cities, the acceptance that full and unrestrained car use cannot be accommodated has lead to traffic management strategies which accept “people” and not “vehicles” and thus positively promote bus priority and place measures for buses at the top of the hierarchy of traffic actions.  Developing cities are likely to have to adopt the same policy as traffic congestion worsens.  However, in developing cities, bus priority can be difficult to implement for both technical and political reasons including (i) where small para-transit vehicles predominate bus lanes are unlikely to be successful, (ii) where bus flows are exceptionally high and bus congestion is a problem, bus priority may have to be combined with bus system reorganisation (iii) where bus systems are only just developing and buses are regarded as a second class mode, reallocation of road space to buses is unlikely, (iv) where there is political and local opposition to road space reallocation.  Bus priority is one of the most effective traffic management techniques to improve efficiency and to assist demand management (by providing an alternative to car use).  These impacts coupled with a high poverty impact should ensure that bus priority is a fundamental element of any traffic strategy.  Improvement in the acceptance of bus priority would be assisted by:

♦            promotion to decision makers/politicians to convince them of the advantages of bus priority;

♦            public consultation (see Chapter 10) to explain schemes and to enable designs to respond to local concerns

♦ dissemination of bus priority planning and design guidelines to cities with little experience in the area; and

♦           commitment to enforcement of traffic management bus priority

3.4         Traffic signals - isolated junctions

3.4.1.      Traffic signals are the primary tool of traffic management.  Traffic signals are used to control traffic movements at conflict points (usually junctions but also at pedestrian crossings or vehicle merges) in order to maximise road capacity and to ensure safe operation.  Additionally, traffic signals can be used to assist the realisation of a traffic management strategy by giving priority to buses, by assisting pedestrians and cyclists and by regulating traffic demand through managing traffic queuing.  Traffic signals can be linked together to co-ordinate the operation of signals over a route, a corridor or an area.  In developed cities, area wide co-ordination has been proved to provide significant benefits in terms of journey times, number of times traffic stops and so on. Area wide co-ordination under the control of a central computer is termed “Area Traffic Control (ATC)" and is discussed in the next paragraph.  However, the impacts of simpler schemes should not be underestimated.  In many developing cities much can be done to optimise the operation of existing signals.  Traffic signals cannot be installed and forgotten; management is needed.  Traffic signals should be optimised to deal with traffic flows as they change over time.  It should be the first task of a traffic management agency, to adjust signal timings to match traffic demand and even with out-dated and limited traffic signal control equipment, benefits can still be captured at little costs and with little effort.

3.5         Traffic signals - Area Traffic Control (computerised area controlled traffic signals systems)

3.5.1.      In dense road networks with significant traffic flows, junctions interact with each other and simple control of traffic signals at isolated junctions is not enough.  Control systems are needed which enable (i) the traffic interactions between junctions to be recognized and/or (ii) priority to be given to one category of system users (usually buses but also pedestrians).  Thus, traffic signals need to be co-ordinated on an network wide basis; this is achieved through the use of some form of central computer control of traffic signals at junctions throughout the road network - termed “Area Traffic Control (ATC)".  ATC is now a key feature of most Bank traffic management projectscomponents even in lower income countries.  Various control systems exist (see Annex ….,) but there is a clear trend towards traffic responsive^[5] systems since real costs are reducing, reliability is increasing and, although the operational benefits of demand response systems may be marginal over simpler systems since (i) the benefits are