Appendix 2: Cost-benefit analysis and accessibility and environment

Crude capacity

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Vehicles using an area have two initial requirements: they must be able to enter the area from the network of surrounding distributor roads, and they must be able to stop there. The satisfaction of these two needs is largely dependent on the flow capacities of the internal roads and the connections to the net-work, and on the amount of space provided for parking. Crude Capacity is a rough measure of the ability of an area to allow vehicles to enter or leave during a stated period of time and to park within the area. It is defined here as the maximum number of vehicles which (assuming all parking spaces are occupied at the start) can leave the car parks in the area within one hour. The Crude Capacity of an area may thus be limited either by the flow capacity or the parking capacity, whichever is the smaller. Table 2 shows the Crude Capacities for the Newbury town centre as it now exists, and for the three alternative schemes.

Table 2: Crude capacity of the Newbury schemes

	Present layout	Scheme A	Scheme B	Scheme C
Car parking spaces (Public and private)	1,600	2,250	4,000	4,500
Possible discharge capacity of internal roads and connections to network (v.p.h.)	2,200*	1,700	3,500	3,500
Crude Capacity (v.p.h.)	1,600	1,700	3,500	3,500

*This figure represents our estimate of the possible flow out of the centre on the roads as they now exist (including present one-way routes); it takes account of the effect on flow of kerbside parking.

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Crude Capacity can be used as a tool to enable both accessibility and environmental capacity to be measured, granted sharper definitions of those terms. These are discussed in the following paragraphs.