URBAN DESIGN International (2000) 5, 123±140 Q 2000 Stockton Press All rights reserved 1357-5317/00 $15.00 www.stockton-press.co.uk/udi

A new paradigm for local development plans A.C. Hall* Professor of Town Planning, Anglia Polytechnic University, Chelmsford

Local development plans commonly work from a paradigm based upon two-dimensional uniform land-use allocations. This approach has difficulty in coping with mixed-uses, urban design principles, urban history and the more general pursuit of more compact and sustainable settlements and does not provide an adequate basis for public participation. A development plan based upon the outlines of urban form in threedimensions with land-uses seen as consequent variables is proposed. It draws upon principles from urban morphology and urban design which translate into a generalised block structure to guide new development. Computer based media would be used for conveying this form of plan. Keywords: land-use; local plans; sustainable development; mixed use; tissues

In all areas of intellectual study and professional practice, much is taken for granted and town planning is no exception. Yet the unexamined parts of a subject are often found to suffer from intrinsic weaknesses, which are played down by the professional culture. Pressure for change grows slowly and is resisted. When it does happen it can be sudden, with complete reversal of the pattern of thinking. In retrospect, it then appears puzzling how the evidence against the previous position could have been ignored for so long. The analysis of this phenomenon in the sciences was described by Kuhn (1970). The purpose of this paper is to draw attention to an equivalent issue in town planning and, using Kuhn's term, to call for a paradigm shift. The topic is the content and use of local plans, that is development plans that propose the relationship of dwellings, roads offices and shops to each other. The concern is with the format of such local development plans, where uniform land-use parcels on a two-dimensional map are used to describe existing and desired land-uses, and to propose locations for new development. It is suggested that this approach has serious flaws. It is not just limiting but can, in some cases, cause *Correspondence: A.C. Hall, (home) tel: 01245 283059 fax: 01245 269032 (work) 01245 493131 x3311 fax: 01245 252646 email: a.c. [email protected]

thinking to be misdirected. It is increasingly inadequate for modern requirements. It is not suggested that development plans are wholly map-based. Clearly, they incorporate planning principles that are not directly spatial in character. However, the two-dimensional land-use paradigm is predominant in thinking behind such plans. What is especially noticeable is the paucity of reference to existing physical form and the absence of explicit three-dimensional proposals. Where it is considered necessary to refer to physical proposals, they are again described in terms of uniform land-use allocations to parcels of land. It is as though land-use preferences are the basic structures on which policies are hung with the characteristics of the physical form of development being a matter that is handled at a later stage of the process. It is argued that the major limitations of this approach relate to dealing with urban design issues and mixed-use proposals. The difficulty in expressing mixed-use proposals is immediately evident. What is also missing is a way of controlling design and realising the outcomes of urban design policies and principles. Indeed, the land-use bias can actually obstruct many urban design goals. It also is an inadequate basis for public participation. Detailed physical proposals are a matter of concern to the lay public and are usually their point of contact with wider planning

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issues. Moreover, all these deficiencies obstruct the pursuit of more compact and sustainable settlement design. It is proposed that the solution lies in a format for development plans that takes the outlines of physical form as its starting point with land-use as a secondary consideration. There are two reasons why urban form can be seen as fairly robust: X

X

morphological studies show that certain elements of form, and combinations of these elements, persist over time as a settlement develops; urban design principles lead to a block form with a standard range of dimensions.

Local development plan goals and policies that relate to physical form should be strengthened. Their interaction with the existing form can produce local objectives and local policy areas based upon them. Different physical options can be generated depending upon the degree of intervention proposed. For example, how much does a policy permit or encourage change? It is argued that these degrees of intervention are equivalent to degrees in change in urban form over time. Morphological techniques developed for analysis of change over time can therefore be used to describe the alternative objectives for the design of localities. The result would be a range of alternative objectives for the physical form of small areas that could be shared with the public and their views sought. The resulting plan would comprise a map showing subdivisions of the plan area according to desired or existing physical form. The degree of intervention for each subdivision would be reflected in the amount of physical detail shown. More general land-use policy and proposals would, of course, still be present but they would be structured in a different way. The potential difficulties posed by attempting to convey this to the public by manual drawing can be overcome by the use of computerbased techniques. It would no doubt be said that introducing elements of physical form into plans would add to their complexity. They would, in consequence take even longer to prepare and approve than they do at present. Against this, it is argued that complexity in plans is essential if they are to be effective. Complexity is already present in current URBAN DESIGN International

planning decision making. The proposal here is that the inevitable complexity of a development plan and the policies guiding it should be made more explicit. Paradoxically, this would make it more accessible to the public and would give more certainty to developers.

Limitations of the current paradigm The British situation1 and its origins The British planning system as a comprehensive national operation dates from the 1947 Town and Country Planning Act. The legislation prior to this had been partial in its application. This did not mean that planning studies done before 1947 were not of a sophisticated nature. The detailed reports were frequently fuller than those that were to follow in the plans drawn up under the 1947 Act. Moreover, they often contained perspective views of proposals, i.e. a three-dimensional representation. However, the plan diagrams they contained were in the form of two-dimensional uniform land-use allocations. In fact, the whole tradition of twentieth century planning had emphasised the separation of land-uses. The separation of noxious industrial processes from residential areas, the growth of edge-of-town trading estates for manufacturing industry, the concentration of shops into town and neighbourhood centres were all part of this trend. Although economic forces were often the cause of this phenomenon, planning thought was pushing in exactly the same direction and encouraging the process along. The 1947 Act brought in development plans that were explicitly map-based. A plan was either a `County Map' or `Town Map' and was accompanied by a written statement and report of survey, both brief by modern standards and often without further illustration. The system that came in with the 1971 Town and Country Planning Act introduced the current system of structure and local plans. It required national coverage at 1

The starting point of this paper is the situation in the Britain as this reflects the author's background. However, it is asserted that there is nothing in the British experience that affects the general applicability of the argument of this paper. At a later stage in the argument, reference is made to innovations in France.

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County Council level through the medium of structure plans, but not at local plan level. Some planning authorities managed to maintain a considerable degree of continuity in urban areas by bringing in new local plans to replace the 1947 Act Town Maps. Unfortunately, many others had failed even to review their 1947 Act plans and large areas of the country moved into a situation where there was no up-to-date development plan in force at local level. The situation was made even worse in the 1980s by the discouragement by the central government of an interventionist approach by local planning authorities, particularly on design issues (DoE, 1980). Only in the early 1990s did new government policy come into force and full national coverage by local plans became a requirement (1990 and 1991 Acts). The proposals map of a current British local plan is normally superimposed on an accurate base-map. It reflects the format introduced in 1971 and continued in 1990. It shows area-based notations, i.e. the boundaries of areas to which particular policies apply. The notations also indicate the status of roads. They show the location of proposed new developments identified in the text of the plan. The Proposals Map is not the plan; rather the plan is the set of policies in the written document. The point is that the policies are either expressed in area terms or have no spatial component. There is no third dimension on which policies are hung. Some policies, such as those regulating house extensions, may have general implications for the third dimension but there is no three dimensional diagram featuring threedimensional proposals. These designations are of uniform land uses. For example, a shopping centre within a residential area requires a separate notation from the housing. Residences or offices over shops cannot be shown. The inadequacy of plans for dealing with sustainable form and mix of use Much is now written about the nature of sustainable forms of development. In England, the government has now issued several reports giving guidance on its physical implications (DETR, 1998; Llewelyn Davies, 1998, Urban Task Force, 1999). What is common to all the advice is the pursuit of a more compact urban form located near to public transport facilities. The aim is to reduce the need to travel, especially the use of the motor car, and achieve energy conservation in

other ways. This requirement is one of specific three-dimensional layouts into which the landuses must fit. Intensification of development, achieving higher density of use, is not something that the conventional development plan, in particular the proposals map, can easily deal with. Mix of use is also implied. In a more compact and intensified urban form the land-uses will inevitably tend to be close together and to overlay in three-dimensions. Mix of use in new development has become a central feature in the discussion of sustainable form (Coupland, 1997; RICS, 1998. It has also been advocated in urban design circles since at least the mid 1980s (Bentley et al., 1985) for other reasons, namely the encouragement of vital and liveable towns. Granted, the lack of precision in the concept can be worrying. What mixes are desirable and in what proportions? These quantities can be, in reality, more important than whether or not there is a mix at all. However, what is unavoidable is the need for development plans to deal explicitly mix of use and with these questions. What concerns us here is whether existing local plan frameworks help or hinder achievement of sustainable form. Clearly, they do not allow for it if they actually inhibit mix of uses by adopting uniform land-use notations. A further inhibition is the lack of a three-dimensional land-use notation. Plans have to deal with changes of use within existing structures as well as guiding new building. In city centres, changes can take place in three dimensions. For example, development can mean the sub-division of dwellings or the change of use of flats over shops to offices. Housing and offices overlaying other uses, however, cannot be shown. Local shops within housing areas must either be shown as very small separate land-uses in precise locations, allowed for as part of a general policy provision for residential areas or seen as an exception to policy. It could be argued that it is the commercial development process that produces the parcels of uniform land-use as a result of the pressure of market forces. However, it could be countered that whereas it is indeed in the interests of the financial backers of developers, it does not reflect the demands of end-users. On the contrary, the real pattern of demand, particularly by smaller concerns, may only be facilitated by the intervention of the planning process to ensure the provision of smaller size offices, houses and URBAN DESIGN International

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other uses. The intervention of the planning system could have the effect of realising the demand for a mix of uses in three dimensions. At present, the two-dimensional uniform land-use approach reinforces the desire of property developers to partition sites for sale as different uses rather than achieve a closely related mix. An observer of a city over time would, indeed, see uniform areas of housing, light industry, office use gradually developing in the 19th and 20th Century city as a result of both development pressures and zoning controls. However, there is something more significant that would also be observed over the same time period: the persistence of particular elements of physical form. Once the large-scale change from agricultural to urban land has occurred, the subsequent changes are largely incidental. Comprehensive redevelopment has occurred only in sections of existing cities. Moreover, this change of use takes place incrementally in small packets. (For example, in residential areas it could mean the loss of a small shop or the gain of a dental surgery.) The plot boundaries, road layouts, and even the outlines of the three dimensional form, can remain static while the land-uses change within them. What, therefore, should be noted is that it is not the physical form that is changing but the uses. The uses change but the structure stays. Even if one building is demolished and redeveloped it retains the same plot and dispositions of plot to street even though the use may change. Even if a number of adjacent buildings are demolished and rebuilt as one new structure, this structure will still reflect the outline plot boundaries around its perimeter and may still address the street even though the use may have changed completely. The present plan paradigm works on the basis of land uses being fixed with physical form varying. In reality, it is often the other way round. The inadequacy of plans for dealing with negotiation and participation in the planning process Since the 1970s the importance of public participation in the planning process has been continuously stressed. The acceptance of a pluralist situation in which planning is but one actor in the development process has given rise to an acceptance of the importance of negotiation. Space precludes a discussion of this history URBAN DESIGN International

here. The question is whether the present development plan system is helpful in the process. The difficulty with the British planning system is its `discretionary' nature. Unlike those of other countries, the development plan is not legally binding on both parties. Although current legislation requires decisions to be made in accordance with the plan, a departure can be made if circumstances merit it. Large parts of the proposals map can be `white land' with no preferred land-use specified. This has produced a reactive culture where the actual nature of policy in detail follows from the action taken when a planning application is determined. Much of the detailed content appears to lay in the mind of the planning officer. Whereas the present local plan format is useful for dealing with debates on the location of significant green-field development or the line of a major road proposal, it is less so for more detailed matters. The absence of proposals on physical form means that the residents of a neighbourhood get no chance to engage in debates on its future form or style. Should it be conserved? Should there be infill or backland development? Instead of the matter being debated with alternatives displayed, the initiative passes to the developer and it is the developer's proposal that is considered by the planning authority with the residents being put in the position of objectors. No full discussion of alternatives takes place. It is often objected that a more prescriptive stance by the planning authority would cramp the style of developers and prevent imaginative options being considered. It would be unpopular with them. On the contrary, it is more likely that it would be very popular with applicants. There is little evidence of, say, volume housebuilders being experimental. Their proposals are driven by constricting economic forces. What they want is certainty and certainty early on in the process. Knowing at an early stage in the process that a proposal is likely to be approved can save a lot of money. Moreover, they would not be prevented from making their representations when the public participation on the design options takes place. The underlying problem is that goals and objectives are not made clear. Negotiations work best if each side makes clear what are their essential requirements as opposed to what is open for

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compromise or even suggestion. The importance of deducing plans from goals and objectives as part of planning theory and method has been stressed since at least the late 1960s. This approach owes much to the controversial `systems' period of planning thought that occurred in the late 1960s and early 1970s. It was, in effect, a replacement for the earlier inductive `survey, analysis, plan' method. The objective-oriented approach had the great advantage of political utility in that it started with a choice of explicit values rather than assuming a unique public interest. This made it capable of responding to a context of pluralist values and public participation. Whether it did so effectively is another question. Plans in Britain usually state goals and objectives but the legal basis of the plan rests not upon them but on `policies'. The `policies' are then used in negotiations (and in enquiries and legal battles where they ensue). The first problem is whether the objectives relate to specific points of concern as opposed to `motherhood and apple pie' statements that all can agree with. Secondly, are they clearly linked to the policies? Thirdly, the policies are often a mixture of desires and procedures. Some indeed may be aims to be achieved but others may be more like the means of achieving them. Both may be policies. Efficient negotiations require clear goals and objectives and the need to be distinguished from procedural matters and suggestions of likely outcomes. The inadequacy of plans for urban design purposes Over the last 15 years there has been a resurgence of interest in urban design in both professional and academic circles. This period has seen the establishment of design principles, such as permeability, legibility and robustness (Bentley et al., 1985) that meet with an increasing degree of consensus. They start from concepts of urban design that lay emphasis on the spaces defined by buildings and concern for the quality of the public realm amid people's enjoyment of it. These principles could be said to have greater importance than matters of style and aesthetics which, in attacks on design control, are portrayed as merely matters of taste. That being said, beauty is important to people and is something that the planning system should try to deliver (or at least deliver protection from ugliness). However, the failings of existing development

plans are particularly acute where the issue of physical form arises in spite of the considerable progress made in including design policy during the 1990s (Punter and Carmona, 1998). Although there has been progress it started from a very low base. The policies commonly tend to generality and `motherhood' statements such as `a high standard of design will be sought' without setting out design principles. In the British context, many local planning authorities cover these matters for parts of their areas only through `supplementary guidance'. However, this begs the question of `if it exists, why is it not in the plan' particularly if it contains, general, not site specific, principles. Examining in particular the two-dimensional uniform land-use paradigm, what are its inadequacies for controlling urban design? Take first the concern of urban design for the spaces defined by buildings. The use of uniform land-use notations can be seen not only to have little provision for this but also to actually cause problems. The boundaries of land-uses are frequently drawn along the lines of roads, rivers and railways. Yet roads and rivers are urban spaces defined by buildings that should be designed as a whole. Different policies for each side of the street or each river bank can cause obvious dislocation. Similarly, parks on a land-use map will have their perimeters defined by the edge of the public open space. For urban design purposes they should be seen as spaces defined by the surrounding buildings and the combination should be planned as a whole. Take next the elements of form from which town space is composed, such as streets, squares and building types. A land-use map gives little guidance. Without some indication of block structure, issues of permeability and legibility cannot be dealt with. Furthermore, the land-use map does not indicate those elements of the form of urban and rural areas that might be permanent as opposed to those that might be liable to change. As emphasised previously, this is a limiting factor in its effectiveness as a controlling mechanism. It also makes it difficult to deal with matters of urban history. Some elements of form, such as plot boundaries, tend to be resistant to change for legal reasons, while retained as a political decision because of their value to the community. It is from these ideas that concepts of conservation and character, clearly popular with the public, arise. In URBAN DESIGN International

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pursuit of a starting point for these ideas and for creating a unifying theme for a new development, principles based on urban history can be of great significance Dealing with complexity Local plans are necessary in order to structure intervention by planning authorities in the development process. Ideally, they should express goals and objectives and facilitate the control of development. Whether or not they do this and how they should be designed to enable them to be effective in this task is the debate that lies behind the argument of this paper. The conclusion drawn is that plans must, inevitably, be complex documents. There is a problem here. The human mind likes to simplify in order to understand. A policy document that deals only with a limited number of options can be useful for teaching and learning but it is restricted in its use for other purposes. It is no good as a control mechanism. This takes us to cybernetics and Ashby's law of `requisite variety' (Ashby, 1956). To control a system the controlling mechanism must be able to exist in as many states as that being controlled. A very simple device cannot control a complex phenomenon, only a limited part of it. The tension between the desire for `simple' and therefore `speedy' procedures and plans and the need to control complex phenomena is very evident in the history of British town and country planning. The 1947 Act plans needed approval by the central government. Their review took a long time and became an increasingly complex process even though the written section was brief by modern standards. The preparation and approval times became longer and longer. The issue was addressed in the 1960s by the PAG Report (Planning Advisory Group, 1966) which recommended a system of skeletal structure plans with local plans and smaller action area plans for areas where significant development, or redevelopment, was expected in the near future. Generally, little precise land-use based content was envisaged outside local/action area plans. The intention was that the structure plans, by eschewing land use details, would be quicker to prepare and approve. Structure plans and `optional' local plans were introduced by the 1968 and 1971 Town and Country Planning Acts. The structure plans rapidly became very complex documents URBAN DESIGN International

that took longer and longer to prepare and approve. What was happening was that the preparation process had to come to grips with the increasingly complex issues surrounding urban expansion, and at the public examination during the approval process, the major developers, local councils and community groups were taking full advantage of the process to advance their interests. Action areas never happened and local plans achieved only a very selective and partial coverage. It was at the end of the 1980s that pressure for complete and detailed local plan coverage resulted in government legislation requiring it (1990 and 1991 Acts). In the absence of an ongoing and continuously updated plan coverage, to introduce one from scratch was an enormously complex undertaking. The size of the task took many by surprise although it was inevitable and should have been foreseen. The problem was that this then brought about calls for a new system that was simpler, easy to understand and, above all, quicker. In effect, what we see here is a circular process. People resist complexity initially but reality forces it upon the procedures governing public policy. Calls are then made for simplification and the cycle restarts. What are really needed are plans and plan making methods that are properly designed to deal with complexity. What is being argued is that development plans must, of their very nature, be complex documents, as they have to be a means of controlling complex situations. Much of this is a matter of how plans are designed and put together. They do not have to be incomprehensible neither do they have to be rigid. On the contrary, rigidity is the reverse of sophistication. The misconception is often that complexity means detail. What it should mean is `details linked to principles' rather than `details as free-standing items'. Planning principles should form the essential structure of any policy document and in a local plan they are vital. It is the `why' of where development should be located that is more important than the precise locational outcome, although both may be needed. The processes of the plan should be clearly understood. The detail will appear highly complex and, indeed, will be highly complex. The important point is that it should readily respond almost organically to changing and intricate political circumstances. It can only do this if it is

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clear on what may be liable to change and what may be more robust over time.

Summary of requirements for a new paradigm Local development plans should be able to: X X

X X X X

make clear goals and objectives especially for urban design2; make clear which elements of existing physical form should be liable to change and which should remain as they are; facilitate use of urban history; control the design of buildings, the spaces they create and to enhance the public realm; facilitate the specification of mix of uses, especially in three dimensions; reflect the relative permanency of physical form in relation to land-use.

Means of creating a new format for development plans Generation of goals and objectives for physical form Hall (1996) has argued that planning goals can be related explicitly to urban design. For example, they could specify the overall character to be pursued for a particular town or could specify the entrance characteristics of major routes into the town. The matter can be taken further with the development of objectives closely related to urban design and desired urban form. He has further proposed clearly separating out the objectives from the criteria for their fulfilment, from advisory information (often sorely lacking) and from control procedures. Standard forms of objective can be identified. These standard types can form a template when preparing design plans and when developing design policy generally. The alternatives can be generated by considering firstly the different degrees of intervention by the planning authority and, secondly, by identifying the different qualities desired within these levels. A possible list, in 2

Whereas this idea is not new, it has not been developed in practice to the degree argued in this paper.

decreasing order of controller intervention, could be: X X X X X

conservation of existing character; specific form or style (with or without a design guide); personalisation with plot; restriction to height/bulk envelope; minimum intervention.

Objectives concerned with urban conservation seek both to preserve the existing plot boundaries and infrastructure and control change within plots. Strict conservation of existing form would imply very little change for all details of the existing townscape. `Specific form or style' may refer to the retention of aspects of an area's character that are to be retained while not to the degree of detail implied by strict conservation. Alternatively, it may refer to new development where what is being sought is a particular urban form. (Examples would be terraced housing form and the case of buildings dominated by landscaping, often known as arcadian form.) We can also have an objective which aims at preserving the existing form while encouraging diversity and individual initiative within plots, termed here personalisation within plot. For example, there is a difference between redeveloping an area of houses and gardens as flats and maintaining this form while allowing extensions to houses as residents choose. The last two types of standard objective (height-bulk envelope, minimum intervention) would not necessarily conserve the existing form and are consistent with redevelopment that aggregates plots and changes street patterns. The design area concept One attempt to structure local plans on a basis other than land-use allocations has been the concept of the design area (Hall, 1996). Although there may be goals and objectives applying generally to the whole town, ones that introduce alternative styles and degrees of intervention (equivalent to degrees of incremental change) will clearly apply to specific localities within the plan area. The design area can be defined as the area to which the objective applies. Its exact boundary will be determined by the interaction between the objective and the existing physical form. The boundaries may vary as the objective changes. This apparently simple idea possesses URBAN DESIGN International

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considerable power. It facilitates sub-divisions that are not necessarily co-terminus with landuse boundaries. It facilitates the handling of mix of uses. Design areas can be defined for spaces together with the buildings that define them such as streets, squares and parks. Design areas should cover the whole of a plan area and in doing so can apply to both town and country. Bringing the design area concept together with the alternative standard design objectives as set out in the previous section, we have a system that facilitates public participation in design plans at an early stage (Hall, 1996). For example, take an area of inter-war suburban housing. There are several design objectives that could apply to this particular type of urban form. In the standard development plan it would carry a housing notation and the policies that applied to it would be those that apply to all residential areas within the plan area. In practice, the potential action that could be taken would vary according to the degree of intervention by the planning authority. At one extreme, representing a high degree of intervention, is the conservation of the area while at the other extreme no objection would be raised to the amalgamation of plots by a developer followed by a total rebuild. In between, are the alterations that might be permitted to existing houses. Even the total rebuild would be subject to a range of intervention by guides and briefs of different degrees of prescription. It has been suggested (Hall, 1990a; 1990b; 1996; 1997) that these alternatives resolve themselves in practice into a small number of discrete alternatives that can easily be put before the residents of the locality. The range of choice results from judgements on the balance between desire for change and the appreciation of the particular qualities of the neighbourhood. There have been precursors of the design area concept in the residential character areas and residential precincts that have been used by some planning authorities to set character requirements for residential areas that do not qualify for conservation area status. For example, the London Borough of Redbridge (Redbridge LB, 1994) has been doing this since 1969 and the London Borough of Sutton (Sutton LB, 1995) for nearly as long. The first explicit use of design areas in practice was by Dacorum Borough Council in its (Dacorum BC, 1995). Design area structures developed for the towns of Hemel Hempstead, Berkhamsted and Tring were subsequently URBAN DESIGN International

adopted as supplementary planning guidance (Dacorum BC, 1998a), then incorporated into the local development plan (Dacorum BC, 1998b) and routinely used in development control decision making. Unfortunately, they cover only residential land-uses and in no case was a choice of objectives for a design area put to the Council or to the public (Hall, 1996). Nevertheless, it has been a pioneering use of the approach and its progress will be of significance. Plan method from urban morphology It can be argued that there is an equivalence between degrees of intervention, as displayed in design objectives, and the stages in incremental growth and redevelopment exhibited by towns (Hall, 1997). A method of systematically describing the growth of towns should therefore provide us with a useful addition to plan language and would enable degrees of planning intervention to be accurately described. Fortunately this is available in urban morphology, particularly in the work of Conzen (Whitehand, 1981). Morphological analysis also has the great advantage of drawing attention to elements of form that persist over time and that can be significant in interpreting the physical manifestations of urban history. In his study of Alnwick, Northumberland, Conzen (1960) analysed the historic development of the town plan from ancient times through to the mid-twentieth century. His conceptual structure focused upon the block plans of buildings in their plots and how they were `contained' within streets and blocks. He observed that the rate of growth outwards from the historic core showed discontinuities over time. His analysis also permitted the recording and understanding of how, over time, types of urban form emerged from within a structure laid down by their predecessors. This process was often accompanied by the persistence of older boundary lines as a result of the constraints of the legal process of conveying land-ownership. His analysis and subsequent synthesis identified plan-units where the built form displayed a morphological cohesion relating to the mode of origin. Conzen's terminology has been subjected to a thorough analysis by Kropf (1993) who has compared Conzen's approach to that of the Italian

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architect, Caniggia. Starting from a different disciplinary tradition, Caniggia developed his own morphological hierarchy with many terms having an apparent equivalence to those of Conzen. There are both significant differences of emphasis between the two systems and much that they have in common. For example, Caniggia talks in terms of lots which have a clear correspondence to Conzen's plots. Both Conzen and Caniggia describe buildings in their lots (plots) arranged along routes (Caniggia's term) and forming plot-series. Caniggia talks of built routes, a term which embraces, amongst other types, the familiar concept of the street. The plotseries can be seen as forming blocks. The plot series/ blocks in combination with streets create particular tissues. Kropf argues that Caniggia's concept of urban tissue can be taken as similar to Conzen's plan-unit combined with building fabric, as employed in his study of Alnwick. Synthesising the work of Conzen and Caniggia, Kropf (1996b)) proposes his own morphological hierarchy based on the idea of containment or levels of complexity with at least seven primary elements: X X X X X X X

tissues (plan-units); plot-series; plots; buildings; rooms; structural elements; building materials.

Drawing on Caniggia, Kropf also proposes the use of the concepts of: X

X

the level of resolution whereby the properties apparent at the desired spatial scale are noted; and the level of specificity, whereby the degree of particularity used is defined.

Looking at a town at a low level of resolution, only the plot-series would be identified as shown by Figure 1. Increasing the resolution results in greater specificity as the plots and then the building within the plots are identified. At each level of resolution different types can be identified. For example, the plot series for a Georgian terrace is quite different from and inter-war suburban street. The different types can be distinguished by reference to the position, outline and arrangement of the elements that compose them (see Figure 2).

Figure 3 shows how levels of intervention can be combined with levels of resolution to form a matrix. The cells of the matrix reveal different levels of specificity. The columns have been given labels to indicate correspondence to certain of the standard objectives. The numbers on the columns indicate different levels of intervention in descending order. What we have, in summary, is a language for conveying desired form that is responsive to degrees of intervention and thereby to plan objectives. To what extent is the morphologically based method described above equivalent to the control of design through building codes? This method has received much attention through the publicity surrounding such examples as Seaside in the USA and Poundbury in the UK (Kreiger and Lennertz, 1992). Discussion of the purpose and use of building codes is a fascinating topic but space precludes a full treatment of it here. To answer the question, however, it can be said that they form part of morphological control but are not the whole story. They represent a high degree of specificity at certain levels of resolution. On the other hand, block outlines and three-dimensional envelopes can be used to structure a large site but they would not constitute a building code. Neither would the preservation of existing buildings or the construction of replicas represent a use of building codes. In other words, building codes can be an important part of the proposed approach but are not essential to it. Morphological control in French practice The principal vehicle for local plans in France is the Plan d'Occupation des Sols, or POS, originally based on legislation of 1973. The POS divides the plan area into zones and specifies the regulations for development control within each zone. Space does not permit a discussion here of all the differences between the zonal planning systems common in Europe and North America and the discretionary system that applies in the UK. The point that must be made, though, is that, although the zonal systems employ small-area designations and often-complex regulations, they are still based on land-use allocations in two dimensions. Indeed, it has been concern about the restrictive nature of this situation, and the desire for more physical controls, that has given rise to innovations in French practice. Legislative changes in 1993 introduced a third generation of POS that URBAN DESIGN International

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Figure 1 Urban tissue at increasing levels of resolution (Kropf, 1996b).

could accommodate control of physical form. The term Qualitatif has been increasingly used to describe such plans. Where they are used, the POSQ can show concern for mixed-uses, URBAN DESIGN International

conservation and the quality of urban form and the public realm (Trache, 1999). Certain

innovative

examples

of

POS

have

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the traditional form and was integrated into the existing urban fabric. The new POS employed morphological controls based upon: X X X

plot dimensions; building form combinations for different plot types; building details (such as shutters and dormers).

Similar approaches were adopted in Mennecy, a commune of 12 000 people 40 km south of Paris (Kropf, 1996a) and Montreuil, a commune of 10 000 people to the east of Paris (Trache, 1999). In the latter case, the town had a historic pattern of plots based upon the horticultural activities which were characteristic of the area before the Second World War. The arrangement of green spaces and walls and the clusters of buildings all served to create a distinctive character. Unfortunately, economic growth and massive redevelopment during the 1960s and 1970s did great damage to it. The revision of the POS in 1993 presented the opportunity not only for the preservation of the remaining features but also to guide future growth in a manner consistent with the historic pattern. Although the analysis and prescription drew on French tradition in urban morphology, they did not neglect the Anglo-Saxon townscape school and regulated views and vistas in the urban landscape. There were four elements of prescription: X X X

Figure 2 Characteristics used in describing elements of urban form taking the plot as an example (Kropf, 1996b).

employed morphological controls to reproduce historic form. One of the first was the plan for Asnieres sur Oise, a commune of 2400 people 35 km north of Paris (Samuels, 1993). A small team of academics from Britain worked with the Commune to produce a replacement for its 1987 POS. There had been a reaction against `pavilion' development, especially for housing, in which a new building was detached both from its neighbours and from the historic context of the village. There was a desire for regeneration and revitalisation but with development that reflected

X

minima and maxima for plot widths and surface areas; ratio of built to unbuilt space including specification of street set-backs; four options for the relationship between density and plot size and the disposition of public and private open space; building heights in pursuit of townscape harmony.

Although British planning officers might find it astounding, this approach was considered `permissive' as design details were not controlled but were left to the discretion of the development control officers. However, the roof shape and bulk of the new building were uniformly controlled using three-dimensional drawings as aids. The examples given so far aimed at ensuring that new development respected an existing historic pattern. The same technique, however, has been URBAN DESIGN International

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Figure 3 A matrix of level of intervention against level of resolution.

used to control large-scale green-field development in France as related by Farthing (1999). He compared the extensive development north of Bristol, where there was very little physical control or design input, with the St. Eloi extension to Poitiers during the 1980s. This was a large addition of 3500 dwellings to the East of the existing city and covered an area of 123 ha. The planning regulations specified: X X X X X X

size and spacing of buildings in blocks; road layout siting of local facilities; layout of neighbourhoods; density; size of dwellings; tenure of dwellings.

None of these had been specified north of Bristol. Although the St. Eloi extension was based on a POS of 1978, the planning thinking stemmed from the same currents of thought and personalities3 that led to the POSQ of the 1990s. 3

Notably the French architect Mellisinos who was to be subsequently involved with Montreuil. URBAN DESIGN International

Plan method from urban design principles The reader will have noted that the plans for Montreuil and St. Eloi contained more than strictly morphological controls. The Montreuil plan included limited use of townscape principles. These contrast with morphological controls by being concerned with the lay perception of the outward appearance of urban form. Aesthetics and legibility can be introduced into new urban development by attending to views, enclosure of space, sequences of views and enclosed spaces (serial vision), texture of buildings and floorscape (Cullen, 1961). The St. Eloi plan was more concerned with structuring new development at a lower level of resolution. The concern for the layout of neighbourhoods and the size and spacing of buildings in blocks relates to important principles from current urban design theories. In the critique of local plans format from an urban design perspective it was pointed out that there are urban design principles that transcend issues of taste and stylistic preference. These principles lead to a definite pattern of urban form, namely

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Figure 4 Springfield Road, Chelmsford ± the original form of large villas in their own grounds.

block structures. These can, and should, be used to guide development within plans. The design principle of permeability leads to grid (albeit deformed) networks of roads with no redundancy of routes and maximum social interaction (Bentley et al., 1985). Buildings should have public fronts and private backs, creating the form of the perimeter block. This is reinforced by urban morphology which shows the development and persistence of this form over several centuries. Designers would argue that this is because it works. In other words, it provides an efficient setting for urban activities. Morphological analysis and urban design principles point to set thresholds in block dimensions. Take, for example, residential and mixed-use areas of two to three storeys in height. Block widths of 80±90 m are common. Much development over the last 30 years has much smaller block widths and dimensions of 50±60 m are common4. This is not accidental but arises from standard principles which can be used to plan new development. The text Responsive Environments (Bentley et al., 1985) notes that the 90 m block `can do for most purposes' but goes on to argue for minimising block size. A method is set out for determining block size from assumptions on parking, privacy, garden space and dwelling size. With regard to dwelling size, the design principle of robustness requires shallow plan

4

The reader may easily check this by applying a scale rule to any detailed map of examples of late 19th and 20th century non-industrial urban areas.

structures that enjoy natural light and ventilation, at least in temperate climates, and can be readily converted to a variety of uses. Taking into account private open space and parking requirements, a rule of thumb calculation for the typical British small town or suburb leads to a block width of 50±60 m across. An equivalent approach, the `ten metre sausage' (Hayward, 1993) yields 40±55 m width blocks. Such dimensions are now typical of much contemporary house building. The implication of these points is that perimeter block structures are a necessary part of the design of new development and their approximate sizes are known in advance. Failure to plan to them would have unsatisfactory results. For any infill on a medium size site (say 100 m square to 300 m square) fitting in 60 m blocks with frontage to roads and backs to existing blocks does not leave much room for manoeuvre and a block structure almost plans itself. The block layouts to be found in the existing form should guide infill. If good planning is to result, blocks are largely predetermined and therefore could, and should, be incorporated in development plans. Worked example Springfield Road, Chelmsford, is part of the old Roman Road from London to Colchester leading out of Chelmsford to the north. From the late nineteenth century onwards, terrace housing was extended outwards from the centre of the town. After the turn of the century, large villas in their own grounds, as shown by the photograph in Figure 4, were constructed along the remainder of URBAN DESIGN International

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Figure 5 Springfield Road, Chelmsford ± redevelopment of infill sites at higher density during the 1950s and 1960s.

the road. During the 1930s, closes of detached house were built in gaps or by demolition of existing properties. This process continued from the 1950s onwards. The result is a mixture of terraces, villas and smaller modern detached houses as shown in Figure 5. Examination of the existing form along the road shows considerable stability in the dimensions of blocks. For the Edwardian and 1930s periods there are large gardens which give a block width of approximately 80 m. Some higher density 1930s housing, and nearly all that from the 1950s onwards, have a block width that is almost standard at 55 m,

irrespective of the design of house and its relationship to the plot. This section of the Springfield Road contains an area of private allotments. Regrettably, they may eventually be developed for housing and so may provide an example of possible infill that needs to be planned for. The proposals map for this part of town in the current Local Plan (Chelmsford BC, 1997). It makes no proposals for this site which is shown as white land. The rest of the road has a residential annotation. Hall (1990a, 1990b, 1996) has set out previously the alternatives in terms of

Figure 6 Alternative design objectives for the Springfield Road example. URBAN DESIGN International

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villa form, terraced form, new build with a choice of form within a design guide or moving towards a more intensive and imposing form with largerscale flats. Figure 6 shows the correspondence of this approach with the morphological controls illustrated in Figure 3. Tissue exercises can be conducted to examine the correspondence of the different forms to the site. A block width of 80 m will take up most of the site. It would be difficult to fit in a perimeter block that would give frontage to roads and back on to existing backs. In addition, housing at such a density would be uneconomic in contemporary circumstances and is likely to be required only in pursuit of an objective of `strict conservation'. The effects of fitting 55 m blocks on to the site are shown by Figure 7. The 27 m arrows in Figure 7(a) show the direction of frontage for half-blocks. Even if some latitude is allowed in this figure, it can be seen that the block structure in Figure 7(c) has an inevitability about it. The likely layout will be clear. Assuming shallow plan structures of approximately 7 m depth, a rear private zone of 15 m depth and a semi-private front of 5 m a physical block form emerges as shown by Figure 7(b). It is suggested that, even with a marginal variation in these dimensions, the form has a definite robustness. It can be extended into the third dimension by showing an envelope that would contain in this case two-storey structures with pitched roofs as shown by Figure 7(d). This envelope would allow for detached properties, terraced houses and flats (i.e. a range of types of buildings and plot-series). For the higher degree of intervention details of form indicated in Figure 6 could be displayed diagrammatically. It would also allow for other uses. Springfield Road already contains small shops, public houses, a hotel and a children's home. If, for example, the policy was to promote more intensive and imposing form then the height of the envelope could be raised to three or four storeys. Presentation of the plan There remains the matter of how to communicate the new form of development plan to the public. The proposals map would now show an outline of block structure in three dimensions coloured to represent preferred land-uses. In areas such as town centres the land-uses may overlay in three dimensions. This is something that is difficult to

convey by manual drawing. Fortunately, computer graphics provide the solution. Not only can they speed up the drawing process and ease the handling of complex graphical techniques but they can also offer new ways of examining the plan. An interactive version can be conceived of with the user navigating in the three-dimensional plan in real time and accessing the appropriate written policies via hyperlinks (Hall, 1996, 1999). Eventually, it should be possible to mount the whole operation on a three-dimensional model of the existing urban or rural area much as the present proposals map is overlaid on a two-dimensional map base. This is now possible in software terms but the hardware is not yet available to make it practical on the desktop. What then will the new proposals map for a local development plan look like? Two scenarios can be presented, reflecting the stages in the development of the computer-based technology. In the near future, what one would see would be a map subdivided into design areas. Only in rural (especially green belt) areas would little physical detail be shown. Even here, though, there would still be objectives relating to landscape and guidance on alterations to buildings. `Greeenfield' sites for new development, and areas proposed for major urban infill would show skeletal block structures. Existing urban areas would show three-dimensional envelopes to the blocks corresponding to existing form or to what will be required when infill or comprehensive redevelopment is envisaged. Although it may at first seem paradoxical, conservation areas would not be shown in three-dimensional detail on this map, as little change to existing structures would be envisaged. Objectives would be conveyed through conservation analyses and advisory material. In the long term, three-dimensional computer models of whole towns, and even the rural areas, can be expected, and planning policies would be hung on these models as hypermedia. These would be used interactively (Hall, 1996). The principal difference in looking at the proposals `map', now a three-dimensional model, would be that the conservation areas would now be explicitly modelled three-dimensions with clear indications where any changes could be made. Outside of conservation areas, the different levels of intervention for each design area would be URBAN DESIGN International

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Figure 7 Tissue exercise showing the emergence of outlines of perimeter block form (a) fitting in 27 m half block widths; (b) the resulting outlines of the blocks; (c) applying shallow plan building types and standard garden sizes to obtain twodimensional building envelopes; (d) building envelopes in three dimensions; (Note that continuous terraces are not necessarily implied. A variety of house types could fit within the outer envelope.)

apparent from the degree of physical detail shown. The more detail, the more control. Sometimes individual buildings would be shown in detail, sometimes just the three-dimensional envelopes. Different versions of the three-dimensional model would appear with different threedimensional colour notations. One version would URBAN DESIGN International

be coloured according to building materials where this was relevant. Another would be coloured in layers in three-dimensions according to the desired land-uses where relevant. The whole would be viewed on a desktop computer via the internet or from a compact disk and used interactively. All features of the model would

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enjoy direct hyperlinks to the written text of the policy.

Conclusion The need for a new paradigm for local development plans has been argued. The present format is constrained by thinking in terms of twodimensional uniform land-use allocations. This limits its usefulness in negotiations and for the control of urban design. It is an inadequate tool for achieving more compact sustainable form involving a mix of land-uses. Principles on which a new development plan should be conceived in terms of outlines of physical form in three dimensions have been proposed. They would be the primary consideration. Land-use allocations would still be an important matter but secondary to the physical guidelines. The degree of physical detail shown would vary within the plan according to the implications of area-specific policies. The elements of form that are to be retained or provided would thus be clearly identified. The result would be a complex document and this complexity is necessary if planning goals are to be attained with an explicit sense of what is going on. This transparency is an essential part of the involvement of the public and the negotiation with developers. Plan and control, although separated out organisationally in British experience, are in reality different aspects of the same process. Firstly, as policy is being implemented, there must exist a conception of policy. Even if it is not written down, there will be an image in the mind of the planning officer. This may be a matter of degree. If only the bare bones are put down on paper then a lot is left to the thought process. It is often argued that it is right to leave a lot of scope to the developer. This is, in reality, an argument about the actors in the process: a discussion of who does what. The problem with this line of thinking is that, when taken to extremes, it represents an abdication of what planning is intended to achieve. Whatever the methods and thought processes that are deployed within the planning process, its outcomes must be physical and the quality of the physical form is the ultimate test in the eyes of the public. This is why what is being proposed here should be seen as a paradigm shift. It accepts that the way plans

are prepared does in itself betray assumed values. Nothing in town and country planning is value free. It emphasises that physical form is important to people. It is the source of both the character of towns, especially where a sense of place provides joy and interest for people's lives, and also the more prosaic human requirements of feeling secure and being able to find the way. All parties to the development process ought to be talking the language of physical form at an early stage in their deliberations. It should be the starting point of the structuring of the discussions of planning policy at the local level. It is not being argued that this is the only thing that planning is about ± far from it. In some parts of the world and at some points in the past this has indeed been argued and it is false. However, it is equally misconceived to think only in land-use and to consign physical form to being a consequence rather than a prerequisite. Although what is being described and argued for is a new local development plan format, the proposals have wider significance. The proposals made are not just for a new form of proposals map but for a different way of thinking about development plans and development control. Changing ways of thinking is a long-term matter and is never easy. The task will take many years to initiate let alone complete. What can be done now is set a new sense of direction.

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Character Study, Discussion Draft. Dacorum BC, Hemel Hempstead. Dacorum Borough Council (1998a) Supplementary Planning Guidance on Development in Residential Area. Dacorum BC, Hemel Hempstead. Dacorum Borough Council (1998b) Dacorum Borough Local Plan First Review to 2011 Deposit Draft. Dacorum BC, Hemel Hempstead. Department of The Environment (1980) Circular 22/80; Development Control Policy and Practice. HMSO, London. Department of The Environment, Transport and the Regions (1998) Panning for Sustainable Development: Towards Better Practice. DETR, London. Farthing, S. (1999) `Land-use Plans and the Implementation of New Urban Development: a Comparative Study' (paper delivered to Planning Futures: the Future of Planning), Sheffield, 29 March 1999. Hall, A.C. (1990a) Generation of Objectives for Design Control. Anglia College Enterprises, Chelmsford. Hall, A.C. (1990b) Generating Design Objectives for Local Areas: A methodology and case study application to Chelmsford, Essex. Town Planning Review 61 287±309. Hall, A.C. (1996) Design Control: Towards a New Approach. Butterworth-Heinemann, Oxford. Hall, A.C. (1997) Dealing with Incremental Change: an Application of Urban Morphology to Design Control. Journal of Urban Design 2 221±239. Hall, A. C. (1999) `A Hypermedia Format for Development Plans' (paper delivered to the Royal Geographical Society with the Institute of British Geographers Annual Conference), Leicester, 6th January 1999. Hayward, R. Talking Tissues. Hayward, R. and McGlynn, S. (eds) (1993) Making Better Places ± Urban Design Now. Butterworth-Heinemann, Oxford. Kreiger, A. and Lennertz, W. (1992) Andres Duany and Elizabeth Plater-Zyberk: Town and Town Making Principles, Harvard Graduate School of Design, New York, Rizzoli.

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Kropf, K. (1993) `An Enquiry into the Definition of Built Form in Urban Morphology' (unpublished PhD thesis), Birmingham, Department of Geography, University of Birmingham. Kropf, K. (1996a) An Alternative Approach to Zoning in France: Typology, Historical Character and Development Control. European Planning Studies 4 717± 737. Kropf, K. (1996b) Urban Tissue and the Character of Towns. Urban Design International 1 247±263. Kuhn, T. The Structure of Scientific Revolutions. (1970) University of Chicago Press, Chicago. Llewelyn Davies (1998) Sustainable Residential Quality ± New approaches to urban living, London, LPAC (with DETR and GOL) Planning Advisory Group (1965) The Future of Development Plans. HMSO, London. Punter, J. and Carmona, M. (1997) The Design Dimension of Planning. E. & F.N. Spon, London. Redbridge, London Borough of Unitary Development Plan. (1994) LB of Redbridge, Ilford. Sutton, London Borough of (1995) Unitary Development Plan. Royal Institution of Chartered Surveyors (1998) Planning Mixed Use Development: Issues and Practice. RICS, London. Samuels, I. The Plan d'Occupation des Sols for AsnieÁres sur Oise. Hayward, R. and McGlynn, S. (eds) (1993) Making Better Places ± Urban Design Now. Butterworth-Heinemann, OxfordSee also: Kropf, K.. Trache, H. (1999) `Promoting urban design in Development Plans: Typo-morphological approaches in Montreuil, France' (paper delivered to Planning Futures: the Future of Planning), Sheffield, 29 March 1999. Urban Task Force (1999) Towards an Urban Renaissance. Routledge, London. Whitehand, J. W. R. (ed) (1981) The Urban Landscape: Historical Development and Management. Papers by M. R. G. Conzen. Institute of British Geographers Special Publication No. 13. London, Academic Press.