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Chapter III – part two: A large town

The Primary Network:
Theoretical network for full car ownership and use: 203–205

 Novermber 1963    The Buchanan Report    Chapter 3ii  
Contents • Chapter 3ii • Theoretical network for full car ownership and use

This theoretical network takes no account, of course, of local environments, existing development, or physical features, nor does it take account of any through traffic

Theoretical network for full car ownership and use

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From the three desire line diagrams we were able to determine the amount of peak-hour movement crossing a series of ‘screen lines’. These gave us specific volumes of traffic to be catered for, and from these we were able to evolve the theoretical road network required to discharge the conditions of full car ownership and unrestrained use. This theoretical network takes no account, of course, of local environments, existing development, or physical features, nor does it take account of any through traffic. (Figure 116)

Fig. 116 The theoretical primary network for full car ownership and use. Distributors shown in red would require to be of motorway standard. The thickness of line indicates the relative size of highway required. Figure 117 shows three alternative methods of attaining continuity of the distributors in the central part of the city.
Fig. 116 The theoretical primary network for full car ownership and use. Distributors shown in red would require to be of motorway standard. The thickness of line indicates the relative size of highway required. Figure 117 shows three alternative methods of attaining continuity of the distributors in the central part of the city.
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The following are the main features of the theoretical network:

  1. Thirteen radials connect the outer suburbs to the main employment areas in and around the town centre. These radials increase in capacity as the centre is approached in order to deal with the increasing loads, but towards the centre they are split up for the better distribution of traffic. To give the required capacity all thirteen radials would need to be designed to motorway standards through the inner suburbs. Six of these would in places need to be eight lanes wide, some of these lanes being reversible (i.e., taking inward traffic in the morning and outward traffic in the evening). Through the outer suburbs only three of the roads (those leading to Bradford, Wakefield and Wetherby) would need motorway specification, the rest could be built as roads for all classes of traffic with intersections on one level, but not, of course, providing direct access to premises.
  2. A series of motorway cross-links, varying from four to six lanes wide, distribute cross-town movements between residential areas and outlying employment areas, and link both these types of area to the main routes out of the city.
  3. In the central part of the city, the network which is needed would be quite impracticable. In theory, the area inside the inner limits shown on the diagram could be served by a series of cul-de-sacs. Six would have to penetrate as far as the central business area, and a further eight would be needed to serve the densely developed belt around this. Such a system would however throw an additional load onto the cross-links, which would then be quite unmanageable. Three possible arrangements have therefore been examined which provide direct access to all parts of the centre (Figure 117). The first is based on a conventional ring and radial system; the second is based on a grid-iron plan with a bias towards the area of greatest traffic generation in the centre. Both of these would be quite impossible in practice, because the distance between the intersections of the network is so small that there would be little or no opportunity to provide access to the very area it sets out to serve. The first also produces the greatest concentration of traffic at the very heart of the centre where new road works would be the most difficult and costly to construct. The third scheme is based on a two-tier system of one-way hexagons, the inner system being more tightly-knit and made independent of the outer by means of connections direct to the network. It is considered that this would be just about feasible, but only if it were possible to redevelop the whole of the area covered by the hexagons, some 2,000 acres.
Fig. 117 Three alternative arrangements for the treatment of distributors within the central part of the city. The first shows a ring and radial system. The second is based on a grid. The third is a two-tier hexagonal system. All three would be virtually impracticable for reasons of space, design, or proximity of interchanges.
Fig. 117 Three alternative arrangements for the treatment of distributors within the central part of the city. The first shows a ring and radial system. The second is based on a grid. The third is a two-tier hexagonal system. All three would be virtually impracticable for reasons of space, design, or proximity of interchanges.
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It is thus concluded that there is no possibility whatsoever, in a town of this size and nature, of planning for the level of traffic induced by the unrestricted use of the motor car for the journey to work in conditions of full car ownership.

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