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Connections and connectivity
Subdivisions provide movement choice and connectivity, while balancing costs, safety, and privacy.
A connected network is based on convenient and logical connections between destinations, based on the most direct route possible.
Subdivision design should allow movement that maximises opportunities for social and economic exchange, while minimising the costs and general need for travel to make such exchanges. The 'right' amount of connectivity should be delivered, instead of any particular fixed standard that may be either too little or too much for a particular site. However, most subdivisions usually require 15 to 35 per cent of the gross developable area to be allocated as movement network space, depending on the density and degree of connectivity being proposed.
Better Design Practice
Street links should be short and direct unless this is not possible because of the land form (topography), important ecological areas or natural features.
Decisions about the number, type and design of roads should be based on how best to integrate the subdivision successfully into the surrounding area, and facilitate travel with the least effort required.
Subdivisions should provide a choice of routes and modes of travel, by having a mix of different activities within a walkable distance, and by minimising the number of lots that are served by only one route through the subdivision. Lots that are accessible by vehicles only should be avoided.
Streets should accommodate a mix of transport types. Safety is enhanced when different transport types use the same space, and travellers can see each other and what is happening across the whole road. In this way, infrastructure can be more efficiently used. For example, a single light pole for vehicles, cyclists and pedestrians rather than multiple poles on multiple separate routes.
The level of connectivity and choice of routes in subdivisions should correspond to the density and land-use mix. As density increases, so should the degree of connectivity and the number of route choices available. Pedestrians should be able to cross roads comfortably without having to deviate significantly from their route to access a crossing point.
Try to provide full street connections (routes that accommodate vehicles, pedestrians and cyclists) wherever possible, unless the landform prevents it. If a pedestrian- and cycle-only link is required, make it wide (more than six metres), straight, as short as possible and well lit.
Rules of Thumb
1. The best outcome is when pedestrians can walk directly when walking from point A to point B within a subdivision, rather than having to 'double back'
2. Street patterns should enable pedestrians to walk to key destinations in less than twice the ‘as the crow flies’ distance
3. Connected roads forming urban blocks are better than a pattern of many cul-de-sacs and a few through roads
4. Limit the use of cul-de-sacs to when:
the topography stops a workable road connection being made
the land t
hat would get access from the through road is very constrained, and joining it to the road network would lead to a significant loss of potentially developable land
a connected road would lead to an unavoidable and significantly adverse landform or habitat loss
a connected road would require unreasonably significant engineering structures and cost
5. Cul-de-sac lenths should be minimised to allow people to see from the mouth of the road to the end, and to promote slow vehicle speeds. These qualities will improve the safety of pedestrians and children playing in the cul-de-sac
6. As the scale and density of a subdivision increases, consider giving more space to streets and other movement links:
In very low density areas, where average lot sizes are larger than 1500m
, limit movement networks to less than 20 per cent of the gross land area in these areas.
In typical suburban areas, where average lot sizes are between 700m
, between 20 per cent and 30 per cent of the gross land area may be appropriate for movement networks in such areas.
In very dense suburban settings, where average lot sizes are less than 400m
, between 30 per cent and 40 per cent of the gross land area is typically allocated to movement networks.
7. Driveways and right-of-ways should serve no more than three lots