22375H urban design MASTER:22375H urban design MASTER
3 creating the urban structure
01/08/2007
Page 38
3.1 the movement framework
3.1.4
Portland, USA
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types of grid
The grid provides choice The time-honoured way of achieving efficient connections is to create a grid, which provides a simple structure, allowing access throughout the area. The form may be orthogonal or more irregular; but its virtues are the same. The grid also offers opportunities for traffic management, allowing restriction of car access in some streets. Grid spacing of 80-100m provides an optimum network for pedestrian and vehicular needs in most circumstances. The size of resulting development blocks has to be checked against proposed uses and building types, and adjusted to suit (see 3.7.2 on block size). In central areas with intensive pedestrian activity, grid spacing of 50-70m provides an optimum circulation network.
Philadelphia, USA
London, West End
However the movement grid of this scale may not be appropriate for structuring the overall urban form. For example, major urban blocks may be over 200 metres or more in any dimension with minor cross streets and footpaths through the blocks. Similarly, parallel street forms may be appropriate, with minor cross routes. Issues of topography, orientation, neighbouring uses and so on are all part of defining the appropriate grid structure for a given development. Birmingham Inner Ring Road: Loosening the collar Project The Birmingham Inner Ring Road was completed in 1971, and was regarded at that time as a classic improvement of its kind. The aim was to remove trunk road traffic from the city core by building a 3.5 mile road around the centre, punctuated by roundabouts at seven junctions. In traffic management terms something of the original aim has been fulfilled, but at the expense of severing the urban fabric at its most vulnerable points. The concrete collar which it has created has broken the traditional links between the City Centre and neighbouring areas. In particular, for people on foot it presents a hostile or impenetrable barrier. The pedestrian subways at the roundabouts are intimidating and humiliating, and have blighted life and activity in the areas around the road. Detail
With part of the road lowered and a wide pedestrian crossing provided, an area once severed now binds together seamlessly
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Contact
Since 1988 Birmingham City Council has adopted a policy of remodelling the ring road, in order to: • link the City Centre to neighbouring areas. • enable City Centre activity to spread into those areas. • create an improved pedestrian environment across the city. In the way traffic is handled the emphasis has shifted to the city’s middle ring road. The most notable aspects of the scheme achieved so far are: • lower Paradise Circus to create a new pedestrian link to Centenary Square and the International Convention Centre; • re-create the Old Square as a pedestrian space on the route from the City Centre to the Law Courts area; • remodel Smallbrook Queensway, including the removal of subways, to create a much improved pedestrian link to the Chinese quarter of the city. Department of Planning & Architecture, Birmingham City Council, Baskerville House, Broad Street, Birmingham B1 2NA Tel: 0121 303 3157
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