Urban Transport Strategy. Management in Developing Countries John A Cracknell, страница 105

The equipment required for each ATC system is similar and comprises (i) on-street signal traffic controllers at junctions, pedestrian crossings etc (ii) communications network (telephone cables or dedicated cables or radio etc) to transmit traffic data and signal system commands two-way between the local or central computers in the control rooms or local centres and the junctions, (iii) data transmission equipment both at junctions and at the central control room, (iv) a central and/or local computer to manage the system and (v) for traffic responsive system, on street traffic detectors (inductive loops, micro-wave, video-processors etc). Many schemes have ancillary equipment such as CCTV to enable the control room operators to monitor conditions.

Inclusion in Bank traffic management projects/component – ATC now features in many Bank urban traffic projects; most cities propose some form of traffic responsive systems and it would not be possible to list all schemes.  Experience of implementation is very mixed and ranges from schemes implemented on time, on budget and without problems (e.g. Leon, Mexico in a Bank project) to schemes involving issues of procurement, specification and agency responsibilities which have proved impossible to resolve and thus eliminated from projects (e.g. Moscow in a proposed Bank project) to schemes which have taken many years to implement, including re-bidding due to procurement problems (e.g. Bangkok although not a Bank project).

Comments and Issues – The advantages of co-ordinated traffic signals control are well documented – reduced overall delays, reduced stop-go traffic flow, optimisation of traffic capacity, improved safety (when pedestrian facilities are incorporated) and decreased downtime for signals as a result of rapid and accurate fault report (inherent in most systems).  However, there have been problems in selection, procurement and sustainability and of ATC systems:

§  System design – increasingly, the issue has arisen as to whether the benefits of traffic responsivedynamic ATC systems are adequate to justify the increased costs and complexity compared to fixed plan systems.  Fixed plan systems require more traffic engineer intervention, traffic data to be collected and updated (a time consuming task in cities where traffic growth rates are high and development is rapid) and are regarded by some cities as “yesterday’s technology”.  Traffic responsive systems require more complex (proprietary) software and hardware, mainly for traffic flow detection and this must be maintained at a fully operational level for the system to function well.  Responsive systems require less traffic engineer intervention but this in itself may be a problem in that traffic engineers may rely on the responsiveness of the system rather than plan and manage the traffic themselves.  However, in general, the trend will be to traffic responsive ATC systems as (i) real costs of equipment are likely to reduce, (ii) detection equipment is now more reliable than formerly and (iii) even though the marginal benefits of traffic responsive systems may be limited, particularly in congested traffic conditions where there is little point in “responding” on main routes, the increase in cost can probably be justified by those marginal operational benefits and by improvement in the image and importance of the traffic management agency and traffic management as a policy;

§  Design and Procurement – planning, design and procurement of ATC under Bank projects has been problematic; issues include:

§  the desire of cities to (i) retain the incumbent equipment suppliers (of an existing ATC system or of existing signals) or (ii) specify proprietary systems or (iii) use supplier credit for at least part of a system.  Such arrangements make compliance with ICB guidelines difficult.  Probably the only solution within a Bank project is for the ATC system to be regarded as a counterpart loan contribution (provided the specified system is regarded as technically satisfactory);