obstruction of vision caused by standing verucles. Even intermittent parking is sufficient to cause the loss of at least half the capacity of the centre lane of the road-the one accommodating the faster vehicles. The combined effect of kerb-side parking and horse-drawn traffic is to reduce the capacity of (for example) a four-lane road from some 2,800 vehicles per hour to about 720, or of a six-lane road from 5,000 to 2,800 vehicles per hour. Clearly, tills use of street space is obtained at a prohibitive w~.
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Clearance sites arising from war damage or during redevelopment could provide temporary parking facilities until reconstruction commences. During the years which will elapse while traffic is growing and road improvements are taking place, extemporised car parks will be very necessary, particularly on the fringes of the central area, if peak-hour traffic is to be kept moving through the present street system. Ultimately, redevelopment of the commercial centre to modern standards with taller buildings should lead to the creation of private parking space within each building block. Commercial loading acconunodation and parking space for places of public assembly can be required for new buildings under powers contained in Section 19 of the Town and Country Planning Act, 1932, and in Section 17 of the Restriction of Ribbon Development Act, 1935; a permanent solution to the kerb-side parking problem may necessitate the provision of car-parking space in connection with all new commercial buildings. [380 Shopping, business and factory frontages on main roads The congestion and restricted movement of traffic in central and suburban business and shopping areas is largely due to the building-up of main-road frontages with direct access from these traffic routes. This practice of using the main road as a service road can be tolerated only up to the stage when growth of traffic exceeds the carrying capacity of the carriageway as depleted by stationary vehicles. With the introduction of mechanically-propelled vehicles, with speeds and interests widely differing from those of the shopper or business caller, the conflicting functions of traffic routes through shopping areas created dangerous conditions for pedestrian and driver alike. To-day the majority of accidents in built-up
areas occur in such circumstances. (Many are also caused by traffic attempting tortuous routes through local streets in an attempt to avoid congested main roads.) [381 The greatly increased traffic flows of the future will necessitate the treatment of the main roads primarily as traffic arteries for the safe and free movement of motor vehicles. Such roads will carry from four to six lines of vehicles at peak hours, so that pedestrians will have to cross by subways. Clearly such roads must not have shopping frontages. Where shops are already there, the road must either be diverled when traffic growth necessitates, or the shops collected into nearby shopping [382 centres when their rebuildi ng is undertaken. Long-term reconstruction to modern standards must ensure that service access to premises adjoining traffic routes is no longer obtained at the expense of the carrying capacity of the main [3113 road. Restrictive effect of junctions and intersections Unless road junctions are properly designed they reduce traffic flow to an extent which severely limits the capacity of the roads leading to them. Many junctions will have to be improved in adva nce of the general road programme to accommodate the earlier stages of post-war traffic growth: no major junction in the region to-day is adequate to deal with the flows which it will ultimately be required to accommodate. Frequent side-street entrances have an effect on capacity at least as serious as that of car parking; traffic turning into and from them obstructs the smooth flow of mainroad traffic in all its lanes. [384 Repairs to public services The present main路 roads are used as routes for the principal public utility services, e.g., sewers, water and gas majns, and electricity and telephone cables. Many of these are under the eaniageways, so that when repairs or service connections have lo be made the capacity of the carriageway is temporarily but nevertheless seriously reduced, often to a single traffic--lane. Not only does congestion and delay occur, but a common cause of accidents is established. (Jss Where these services follow main traffic routes they should be duplicated and laid under the footpaths and side verges. GeneraUy the widths 75