Design manual
Design Manual for Urban Roads and Streets
The design of roads and streets within urban speed limits.
Department of Transport, Tourism and Sport and Department of Housing, Planning and Local Government · 2019 (version 1.1) · 165 pages
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- 39May 2019 (Version 1.1) CITY CENTRE TOWN CENTRE VILLAGE CENTRE SHOPPING CENTRE 1 MIXED USE CORE MEDIUM/HIGHER DENSITYEARLY RESIDENTIAL 2 LOW DENSITY RESIDENTIAL3 BUSINESS PARK3 INDUSTRIAL ESTATE NOTE: 2. Some areas may have densities below 35 dwellings per hectare where sites are long and narrow. From a street design perspective they are compact neighbourhoods due to their narrow frontages (i.e. fine grain) and proximity of dwellings to the street/continuity of the built form (i.e. strong sense of enclosure). NOTE: 3. The examples listed above are illustrative of existing contexts. Future development or retrofit schemes in any of the contexts indicated above must be subject to national policy on sustainable development as set out in relevant policy documents and to the principles, approaches and standards contained within this Manual. Cork Bray, Co. Wicklow Killiney, Co. Dublin Blanchardstown, Co. Dublin Knocknacarra, Galway Limerick Donnybrook, Dublin Adamstown, Co. Dublin City West, Co. DublinPouladuff, Cork birds eye images from www.bing.com/maps/
- Design Manual for Urban Roads and Streets40 Transition Areas There are also those Contexts where designers should provide a transition from those roads built to NRA DMRB (historic) or DN-GEO-03031 Rural Road Link Design (2017) led standards to those roads and streets described by this Manual. These include (and as further detailed in Section 3.3.4 Wayfinding): • In Business Parks/Industrial Estates undergoing a period of transition toward more intensive forms of commercial and residential development, designers should cater for increased levels of pedestrian activity (see Figure 3.6). • In the Rural Fringe when moving between rural areas and cities, towns and villages (see Figure 3.7). Managing transitions within Business Parks/Industrial Estates presents a series of challenges to designers. As development within these areas intensifies, designers are encouraged to move toward standards that are better suited to densely populated urban areas (i.e. Centres and/or Neighbourhoods). However, the implementation of standards which seek to slow vehicular movement and increase pedestrian mobility (such as narrower carriageways or tighter corner radii), may be more difficult to implement due to the manoeuvrability requirements of larger vehicles. Under such circumstances designers may consider additional mitigation measures (as further detailed in Chapters 4 and 5). Many Rural Fringe areas act as transitional Gateways between the rural and more urban/suburban forms of development. These areas may be treated as a Transition Zone (see Section 3.3.4 Wayfinding). In such circumstances, designers should implement a series of measures aimed at highlighting this transition and slowing drivers. Further advice in this regard is also contained throughout Chapters 4 and 5 and within Advice Note 1: Transition Zones and Gateways. Figure 3.6: Sandyford Industrial Estate, Co. Dublin, is undergoing a process of significant change from an industrial estate to a mixed use area of centre/urban qualities. The new crossing in the foreground in one example of how designers are responding to its rising place value and the needs of pedestrian users. Source: Google Street View Figure 3.7: Example of a road that goes through a period of transition between a rural area (top) to that of a town/urbanised area (bottom) (image source: Google Street View). Source: Google Street View RURAL RURAL FRINGE TOWN
- 41May 2019 (Version 1.1) 3.3 Permeability and Legibility 3.3.1 Street Layouts The movement towards more integrated and sustainable forms of development will result in a shift away from dendritic street layouts to highly connected networks which maximise permeability, particularly for pedestrians and cyclists. When designing new street networks designers should implement solutions that support the development of sustainable communities. In general, such networks should: • be based on layouts where all streets lead to other streets, limiting the use of cul-desacs that provide no through access. • maximise the number of walkable/ cycleable routes between destinations. Maximising the connections within a site will allow the street network to also evolve over time to meet local accessibility needs. This will limit the use of cul-de-sacs that do not allow through accessibility for all users. These streets should be limited to areas where mid-block penetration is desirable (see Section 3.3.2 Block Sizes). Figure 3.8 illustrates three network typologies that can be adapted to the needs of place. Street networks that are orthogonal (see Figure 3.8a) in nature are the most effective in terms of permeability (and legibility). Within the Irish context orthogonal or grid layouts are often found within the Centres and Neighbourhoods developed between the Georgian and Edwardian periods (e.g. Limerick City Centre). More recent successful examples include Dublin Docklands and Belmayne, Co. Dublin. Street networks that are curvilinear (see Figure 3.8b) may also be highly effective. Within the Irish context, these types of grids are often found within Suburbs developed from the 1920s onwards (e.g. Marino and Cabra, Dublin). More recently designers have successfully used similar geometric patterns in higher density developments to draw people toward spaces, highlighting Focal Points (see Section 3.3.4 Wayfinding) and creating attractive curvilinear streetscapes. More recent successful examples include Clongriffin, Co. Dublin. Figure 3.8: Permeable street layouts may be formed via a number of different configurations including examples of the more rigid orthogonal, curvilinear and/or organic. a) ORTHOGONAL LAYOUT BELMAYNE b) CURVILINEAR LAYOUT CLONGRIFFIN c) ORGANIC LAYOUT POUNDBURY
- Design Manual for Urban Roads and Streets42 Street networks that are organic (see Figure 3.8c) have usually developed over time in a haphazard manner, but can be highly connected. As noted in the Urban Design Manual (2009) the more organic layout of some small villages can be very different from orthogonal grids, but perform a similar function. These types of layouts can be found within many Medieval or Early Modern Centres (such as Lusk, Co. Dublin). Organic layouts introduce place benefits by introducing variety and intrigue. An example where designers have recreated these qualities within a recently developed area can be found in Poundbury, Dorchester, in the UK. The creation of a permeable network is a multi-layered process. The process should begin with a site analysis that identifies any constraints to the development of a particular network (such as environmentally sensitive areas, topography, existing structure etc). The process then should move into a design phase. This should outline: • Points of access. • The major destinations (such as Centres and nodes). • The main strategic connections between destinations. This process will identify the basic framework for the application of a more detailed street hierarchy. Figure 3.9 outlines how this process can evolve in four simplified stages of design. This process should also be expanded to take account of: • The likely number of trips generated by each destination. This may result in additional Link Streets that are designed to cater for larger volumes of traffic (and in particular buses). • Movement prioritisation measures for buses, particularly along Arterial and Link streets and within Centres (see Section 3.4.3 - Bus Services). • The creation of a cycle network.2 2 Chapter 3 of the National Cycle Manual (2011) outlines a 7 step process for Network Planning. • Possible restrictions on the movement of private vehicles (see Section 3.4.1 Vehicular Permeability). Designers may refer to Appendix 1 of the Urban Design Manual (2009) which provides several examples of an analysis process and the subsequent design outcomes. This includes a number of extensions to existing areas. Understanding the historical context of a place will give a greater appreciation of the way it evolved and the street patterns that exist. This is particularly important for extensions to existing towns and villages and should help avoid the imposition of incongruous street layouts.
- 43May 2019 (Version 1.1) Figure 3.9: Illustrations of the creation of a structured and permeable grid network as a multilayered process. 1. CONNECTION OPPORTUNITIES The site analysis should identify the connection opportunities (1) within a site including the major destinations (such as Centres and nodes) within it and access from the surrounding area. 2. MAIN STRATEGIC LINKS The connection options form the basis for the main Strategic links (2) into and through the site. These routes will form the principle corridors for the movement of pedestrians, cyclists, public transport and vehicles within and through the site. They should be as direct and as continuous as is possible within the constraints of any site. 3. ACCESS AND CIRCULATION Further links and connections will be needed to allow for permeability within a network. The creation of routes for (3) access and circulation ensure all parts of the site are accessible from a number of different directions. 4. DETAILED DESIGN As the process moves into (4) detailed design, designers will need to address further structural issues, including block layouts, mobility levels for different users and the street hierarchy. ARTERIAL LINK LOCAL
- Design Manual for Urban Roads and Streets44 3.3.2 Block Sizes Designers must also have regard to size of blocks within a street network and how they impact on permeability. Smaller, more compact blocks should be focused around Centres to optimise connectivity. Larger block sizes may occur away from Centres, through less intensively developed areas (see Figure 3.10). With regard to block dimensions:3 • A block dimension of 60-80m is optimal for pedestrian movement and will sustain a variety of building types. This range of dimensions should be considered for use within intensively developed areas, such as Centres, to maximise accessibility. • Larger blocks within Centres and Business Parks/Industrial Estates may be required to cater for larger commercial or civic developments. In such cases mid-block pedestrian links should be provided. • A block dimension of up to 100m will enable a reasonable level of permeability for pedestrians and may also be used in Neighbourhoods and Suburbs. Within a development there may be sections of a site where accessibility requirements are low or where the site constraints may not facilitate a more permeable block pattern. Where this occurs designers may need to apply larger block dimensions. However, all efforts should be made to ensure the maximum block dimension does not exceed 120m. On larger and/or irregular blocks short cul-de-sacs may also be used for midblock penetration to serve a small number of dwellings and to enable more compact/ efficient forms of development (see Figure 3.11). 3 Designers may also refer to Section 3.7.2 of the UK Urban Design Compendium (2000) for further guidance on block sizes and permeability. Figure 3.10: Optimal block dimensions in varying contexts that will promote a walkable neighbourhood. 60m 80m OPTIMAL BLOCK SIZE 100m 60m LARGER BLOCK Figure 3.11: An example of a short cul-de-sac which is used to penetrate an irregular/larger block and serves a small number of dwellings. 120m LARGE/IRREGULAR BLOCK Private Parking Court
- 45May 2019 (Version 1.1) 3.3.3 Retrofitting Smarter Travel (2009) recognises that sustainable travel can be supported through retrofitting and requires that local authorities prepare plans to retrofit areas in order to create more sustainable neighbourhoods.4 The retrospective application of a permeable network to increase connectivity levels within more segregated street patterns can be problematic. The dendritic nature of some of these street patterns often means that connection opportunities are very limited. Well placed links can lead to substantial benefits for the local community in terms of reducing walking distances to essential services. Research has found that increased local movement is also beneficial to security as it can increase levels of passive surveillance.5 Designers should seek to engage closely with local communities to highlight such benefits. 4 Refer to Action 4 of Smarter Travel (2009). 5 Refer to An Evidence Based Approach to Crime and Urban Design (2009). Figure 3.12 illustrates two recently constructed pedestrian and cyclist connections made in Dublin. Both examples significantly reduced walking times to public transport (top) and local shops (bottom). The bottom example included consultation sessions and a survey of residents prior to the formal planning process. This survey indicated that 86% of the local community (located within a 10 minute walking catchment) supported the link. Post construction monitoring has also found up to 500 people a day using the link.6 There are also a number of processes and design principles that may also assist in gaining greater community support: • Focus on the provision of pedestrian/cyclist only links. 6 Source: South Dublin County Council. Figure 3.12: An example of two local permeability projects in Dublin which have significantly improved local access to the LUAS (top) and local shops (bottom) for pedestrians and cyclists. These links formalised routes that were used by locals which previously involved walking across unlit fields, muddy patches and/or climbing over/through fences. BEFORE BEFORE AFTER AFTER
- Design Manual for Urban Roads and Streets46 • Rather than seeking to retrofit a fully permeable network (i.e. maximising all connections), focus on key desire lines where the maximum gain can be achieved through the minimum amount of intervention. • Ensure any plan clearly highlights reductions in journey times, walking distances etc. (see Figure 3.13). • Identify potential reductions in private vehicle use or increases in cycling and walking. • Ensure links are short, overlooked, have clear sight lines and are well lit to mitigate anti-social behaviour. Longer links should be limited to those which go through areas of open space. • Implement a package of landscape improvements that will directly add to the attractiveness of an area. Figure 3.13: Connectivity study undertaken for the Tallaght Town Centre LAP identified how a short link intervention through an area of open space (achieved by providing a path, crossing and partial removal of a fence) could significantly increase the number of households within the 400m walking catchment to the LUAS station (base map source:www.bing.com/maps). LUAS Current 5 minute walking catchment Potential 5 minute walking catchment • Implement parking management plans (such as pay and display/controlled parking permits) to mitigate any possible influx of vehicles seeking to ‘park and ride’ on neighbouring streets. • Where possible, focus on formalising routes which are currently used by more able pedestrians but due to barriers are not suitable for use by the mobility Impaired and disabled.
- 47May 2019 (Version 1.1) 3.3.4 Wayfinding Wayfinding, or legibility, relates to how people can find their way around an area. For pedestrians and cyclists this is of particular importance as they are more likely to move through an area if the route is clear. There are many tools that designers can use to provide a series of design cues by which people can orientate themselves. For example, changes in building height and form, materials and finishes and landscape features. From a broader perspective designers should ensure that journeys through the network are relatively straightforward. In general: • The more the orthogonal street layout the more legible it will be (as well as being the most connected). • The network should be structured to draw people towards Focal Points such as Landmarks, Gateways and other civic buildings and spaces. Figures 3.14 and 3.15 illustrate how legibility can be achieved with street networks by drawing people toward key destinations or Focal Points. Figure 3.14: Poundbury, Dorchester, UK. The network of interconnecting streets directs people toward a central location, whilst also allowing for route choice (base map source: Google Earth). Figure 3.15: The Newcastle LAP (South Dublin County Council) illustrates how movement within the village is structured by connecting major Focal Points, which are also used to slow/discourage through traffic. Focal Point Connection
- Design Manual for Urban Roads and Streets48 Figure 3.17: Example of a Gateway from Adamstown, Co. Dublin, where changes to the built form and landscaping treatments add to the sense of enclosure and create a formal entry point. To Increase effectiveness the streets around Focal Points require a more individualised design response that highlights their high place value. These are further discussed below in relation to their implications for street design. Landmarks and civic buildings and spaces Landmarks are features that stand out from their surrounds and are valued by the broader community for their aesthetic and/or historic qualities. Examples include a tall or historic building, archaeological site or landscape feature. Civic buildings and spaces generally include local facilities such as areas of open space and buildings of civic importance. Areas of open space include parks, squares or plazas. Buildings of civic importance include a wide range of places such as schools, churches, hospitals and other institutions. Designers should highlight these Focal Points by (see Figure 3.16): • Ensuring that pedestrian facilities are adequate to cater for large number of visitors. • Traffic is calmed using surface treatments and other elements that further highlight the importance of the place. Gateways Gateways are used to demarcate a point of arrival from one place to another. They are important placemaking tools as they form the ‘first impression’ of a place. Gateways are also an important traffic-calming tool as they can be used to inform drivers of a change in driving conditions ahead. Common forms of gateways in Ireland occur at the entrances to residential estates and on National Roads at approaches to villages. To create an effective gateway that adds value to place designers should: • Use elements of place such as landscape and built form to create a strong sense of enclosure (see Figure 3.17). • Use material changes and street furniture as supplementary measures (see Figure 3.18). Figure 3.16: Illustration of surface treatments in Dundalk, Co. Louth. These treatments enhance the sense of place by expanding the square into the adjacent streets and are an effective way of improving pedestrian mobility and calming traffic.
Source Department of Transport, Tourism and Sport and Department of Housing, Planning and Local Government: Design Manual for Urban Roads and Streets (2019 (version 1.1)) · Licence the publisher's termsText read from the publisher’s PDF; tables, maps and drawings do not survive as text, and page numbers are the PDF’s (its first page is 1). Check the original before relying on a passage.