« Previous | Contents | Next »
Listen
G1 Layout and Connectivity
CHAPTER AIMS
- Set out design concepts for the structuring of towns and cities.
- Set out principles for walkable neighbourhoods.
- Illustrate appropriate layouts and street forms.
- Consider internal permeability and external connectivity.
- Give advice on crime prevention.
G1.1 PLANNING FOR THINGS YOU CANNOT EASILY CHANGE LATER
G1.1.1 The way streets are laid out and how they relate to the surrounding buildings and spaces has a great impact on the aesthetic and functional success of a neighbourhood. Certain elements are critical because once laid down, they cannot easily be changed. These issues are considered in the masterplanning and design coding stage, and need to be resolved before detailed design is carried out.
G1.1.2 This chapter highlights the issues likely to be encountered in developing detailed designs, and ways of dealing with them. There are also tips on avoiding unwanted consequences of particular design decisions.
Figure G1.1 Integrating new developments into the existing urban fabric is essential (source: The Urban Design Compendium1).
G1.2 THE MOVEMENT FRAMEWORK
G1.2.1 A key consideration for achieving sustainable development is how the design can influence how people choose to travel. Designers and engineers need to respond to a wide range of policies aimed at making car use a matter of choice rather than habit or dependence. Regional and local transport strategies can directly inform the design process as part of the policy implementation process.
G1.2.2 It is recommended that the movement framework for a new development be based on the user hierarchy as introduced in Section 3.5.5. Applying the hierarchy will lead to a design that increases the attractiveness of walking, cycling and the use of public transport. Delays to cars resulting from adopting this approach are unlikely to be significant in residential areas. The movement framework should also take account of the form of the buildings, landscape and activities that form the character of the street and the links between new and existing routes and places (Fig. G1.1).
Figure G1.2 Internally permeable neighbourhoods lacking direct connections with one another - to be avoided (source: Marshall 2005, Streets and Patterns. London: Spon Press).
G1.2.3 Street networks should, in general, be connected. Connected, or 'permeable' networks encourage walking and cycling, and make places easier to navigate through. They also lead to a more even spread of motor traffic throughout the area and so avoid the need for distributor roads with no frontage development. Research 2 shows that there is no significant difference in collision risk attributable to more permeable street layouts.
G1.2.4 Pedestrians and cyclists should generally be accommodated on streets rather than routes segregated from motor traffic. Being seen by drivers, residents and other users affords a greater sense of security. However, short pedestrian and cycle-only links can be acceptable if designed well. Regardless of length, all such routes in built-up areas, away from the carriageway, should be barrier-free and overlooked by buildings. Narrow routes hemmed in by tall barriers should be avoided as they can feel claustrophobic and less secure for users.
CONNECTING LAYOUT TO THEIR SURROUNDINGS
G1.2.5 Internal permeability is important but the area also needs to be properly connected with adjacent street networks. A development with poor links to the surrounding area creates an enclave which encourages movement to and from it by car rather than by other modes (Fig. G1.2).
G1.2.6 External connectivity may often be lacking, even where layouts generally have good internal permeability. Crown Street, Glasgow, is shown in Fig. G1.3a, with an indication of where connectivity was not realised.
G1.2.7 The number of external connections that a development provides depends on the nature of its surroundings. Residential areas adjacent to each other should be well connected, as should residential areas with local centres or high streets.
G1.2.8 To create a permeable network, it is generally recommended that streets with one-way operation are avoided. They require additional signing and result in longer vehicular journeys.
THE HIERARCHIES OF PROVISION
G1.2.9 If road safety problems for pedestrians or cyclists are identified, conditions should be reviewed to see if they can be addressed, rather than segregating these users from motorised traffic. Table G1.1 suggests an ordered approach for the review.
G1.2.10 These hierarchies are not meant to be rigidly applied and there may be situations where it is sensible to disregard some of the solutions when deciding on the optimum one. For example, there would be no point in considering an at-grade crossing to create a pedestrian/cyclist link between developments on either side of a motorway. However, designers should not dismiss out of hand solutions in the upper tier of the hierarchy.
G1.2.11 It is recommended that the hierarchies are used not only for a proposed scheme but also for connections through existing networks to local shops, schools, bus stops, etc.
G1.3 BUILDING COMMUNITIES TO LAST
G1.3.1 Good design is a key element in achieving the Scottish Government's aim to create thriving, vibrant, sustainable places. Sustainable places meet the diverse needs of existing and future residents, are sensitive to their environment by minimising their effect on climate change, and contribute to a high quality of life. They are safe and inclusive, well planned and promote social inclusion, offering equality of opportunity and good services for all.
Figure G1.3 Crown Street, Glasgow: (a) the Crown Street development in the background is separated from the main road to the city centre; and (b) map.
Table G1.1 The hierarchies of provision for pedestrians and cyclists
* Adjacent-use routes are those where the cyclists are segregated from pedestrians.
G1.3.2 Areas of local amenity should be evenly distributed, with good connectivity, so that the overall layout encourages access by walking or cycling, and shortens the distances travelled by car (Fig G1.4).
G1.3.3 When considering a site there needs to be a broad understanding of its historic development and its relationship with other communities, whether at the village, town or city scale (Fig G1.5).
G1.3.4 The provision and viability of facilities needs to be assessed in relation to the location and scale of proposals. In many cases, it may be better for a new development to reinforce existing centres and facilities rather than providing alternative facilities. The greater the density of development, the more facilities can be supported.
Figure G1.4 (a) dispersed and car-dependent versus (b) traditional, compact and walkable layout
Figure G1.5 The plans of many Scottish villages, towns and cities illustrate different patterns of development over time, from (1) historic cores, through to (2) experimental 'Radburn' layouts from the 1960s, to (3) recent cul-de-sac layouts.
G1.4 THE WALKABLE NEIGHBOURHOOD
G1.4.1 Walkable neighbourhoods are typically characterised by having a range of facilities within 10 minutes (up to about 800 m) walking distance of residential areas which residents may access comfortably on foot. However, this is not an upper limit. SPP173 states that:
'Within an approach to integrated land use and transport planning, mode of personal travel should be prioritised according to the following principles:
- walking: the most sustainable form of travel, capable of substituting for the car over short distances with very significant health benefits and environmental gains.
- cycling: a sustainable form of transport with significant health benefits and environmental gains
Figure G1.6 The Walkable Neighbourhood
Designing Streets encourages a reduction in the need to travel by car through the creation of mixed-use neighbourhoods with interconnected street patterns, where daily needs are within walking distance of most residents (see figure G1.6).
G1.4.2 By creating linkages between new housing and local facilities and community infrastructure, the public transport network and established walking and cycling routes are fundamental to achieving more sustainable patterns of movement and to reducing people's reliance on the car. A masterplan (or scheme layout for smaller-scale developments) can help ensure that proposals are well integrated with existing facilities and places.
G1.4.3 Density is also an important consideration in reducing people's reliance on the private car. SSP173 encourages a flexible approach to density, reflecting the desirability of using land efficiently and the need to promote higher density development in places well served by public transport. Residential densities should be planned to take advantage of proximity to activities, or to good public transport linking those activities. Better Places to Live By Design4 advises that a certain critical mass of development is needed to justify a regular bus service, at frequent intervals, which is sufficient to provide a real alternative to the car.
G1.5 LAYOUT CONSIDERATIONS
G1.5.1 Streets are the focus of movement in a neighbourhood. Pedestrians and cyclists should generally share streets with motor vehicles. There will be situations where it is appropriate to include routes for pedestrians and cyclists segregated from motor traffic, but they should be short, well overlooked and relatively wide to avoid any sense of confinement. It is difficult to design an underpass or alleyway which satisfies the requirement that pedestrians or cyclists will feel safe using them at all times.
G1.5.2 The principle of integrated access and movement means that the perimeter block is usually an effective structure for residential neighbourhoods. A block structure works in terms of providing direct, convenient, populated and overlooked routes. In addition, it makes efficient use of land, offers opportunities for enclosed private or communal gardens, and is a tried and tested way of creating quality places (Figs G1.7 and G1.8).
Figure G1.7 Perimeter blocks enclosing a pleasant communal open space
Figure G1.8 A roads-dominated layout with buildings that have a poor relationship to the road ( EDAW, Drumchapel).
G1.5.3 Several disadvantages have become apparent with housing developments built in the last 40 years which departed from traditional arrangements. Many have layouts that make orientation difficult, create left over or ill defined spaces, and have too many blank walls or façades. They can also be inconvenient for pedestrians, cyclists and bus users.
G1.5.4 Within a block structure, the designer has more freedom to create innovative layouts. The layouts in Fig. G1.9, and variations on them (such as a 'broken grid' with the occasional cul-de-sac), are recommended when planning residential and mixed-use neighbourhoods.
Figure G1.9 Variations on the block structure.
GEOMETRIC CHOICES AND STREET PATTERN
G1.5.5 Straight streets are efficient in the use of land. They maximise connections between places and can better serve the needs of pedestrians who prefer direct routes. However, long, straight streets can also lead to higher speeds. Short and curved or irregular streets contribute to variety and a sense of place, and may also be appropriate where there are topographical or other site constraints, or where there is a need to introduce some variation for the sake of interest. However, layouts that use excessive or gratuitous curves should be avoided, as they are less efficient and make access for pedestrians and cyclists less direct.
G1.5.6 Geometric choices and street pattern should be based on a thorough understanding of context.
G1.5.7 Conventional cul-de-sacs, which are often favoured by new home owners, can offer some benefits. For example, their design creates an open area that children can play in, and without through traffic residents are more likely to use their front garden space. Their success is largely dependant on the size and layout of the cul-de-sac, the detailing of road carriageways, boundary treatments (or lack of them), how parking is addressed holistically throughout the development and the attitudes of local residents. Consequently, conventional cul-de-sac layouts without inter-connection are discouraged. The preference is networked routes and spaces which connect new residential areas together and link with existing development forms.
Figure G1.10 A good example of a pedestrian/cycle route. It is short, direct and overlooked.
G1.5.8 Cul-de-sacs may sometimes be required because of topography, boundary or other constraints. Cul-de-sacs can also provide the best solution for developing awkward sites where through routes are not practical (Fig. G1.10). Caution must, however, be exercised when planning for cul-de-sacs, as they may concentrate traffic impact on a small number of dwellings, require turning heads that are wasteful in land terms and lead to additional vehicle travel and emissions, particularly by service vehicles. Any through connections for pedestrians and cyclists should be provided and well overlooked with active frontages.
G1.6 CRIME PREVENTION
G1.6.1 The layout of a residential area can have a significant impact on crime against property (homes and cars) and pedestrians. Section 17 of the Crime and Disorder Act 19985 requires local authorities to exercise their function with due regard to the likely effect on crime and disorder. To ensure that crime prevention considerations are taken into account in the design of layouts, it is important to consult police Architectural Liaison Officers as advised in Planning Advice Note 77: Designing Safer Places. 6
G1.6.2 To ensure that crime prevention is properly taken into account, it is important that the way in which permeability is provided is given careful consideration. High permeability is conducive to walking and cycling, but can lead to problems of anti-social behaviour if it is only achieved by providing routes that are poorly overlooked, such as rear alleyways.
G1.6.3 Designing Safer Places highlights the following principles for reducing the likelihood of crime in residential areas.
Early discussions with the local authority and police can help to identify any physical, social and economic circumstances that could have an impact on local crime characteristics. Understanding the problems should enable better design.
Buildings should be orientated to provide natural surveillance of footpaths and public spaces.
An appropriate mix of uses can often encourage activity and movement at all times. Although mixed uses should be compatible.
There is general acceptance that high quality external lighting can help to reduce the incidence of crime. It can add vitality to an area, enhancing its attractiveness and sense of place.
Pedestrian routes should have an open aspect, be well lit and have a good level of surveillance. The pedestrian should be able to view the full length of the path on entry rather than negotiate blind corners or recesses.
Figure G1.11 Active frontage to all streets and to neighbouring open space should be an aim in all developments. Blank walls can be avoided, even on the return at junctions, with specially designed house types.
G1.7 STREET CHARACTER TYPES
G1.7.1 Traditionally, road hierarchies (e.g. district distributor, local distributor, access road, etc.) have been based on traffic capacity. As set out in Chapter 2, street character types in new residential developments should be determined by the relative importance of both their place and movement functions.
G1.7.2 Examples of the more descriptive terminology that should now be used to define street character types are:
- high street;
- mixed-use street
- brae
- crescent
- end
- gait
- mews
- neuk
- terrace
- way
- shopping street;
- avenue
- courtyard
- cross
- feus
- lane
- mill
- row
- vennel
- wynd
G1.7.3 The above list is not exhaustive. Whatever terms are used, it is important that the street character type is well defined, whether in a design code or in some other way. The difference in approach is illustrated by Figs G1.12 and G1.13.
Figure G1.12 Alternative proposals for a development: (a) is roads-led; while (b) is more attuned to pedestrian activity and a sense of place.
Figure G1.13 (a) Existing development in Upton turns its back on the street; while (b) a later development has a strong presence on the street. The latter was delivered using a collaborative workshop design process and a design code.
« Previous | Contents | Next »