The Fused Grid
A Neighbourhood and District Layout Model
Traditional suburban street patterns and their impacts
A problem with conventional subdivision loop and curl street patterns is that they inhibit walking and are disorienting and confusing to pedestrians as well as to drivers. They provide tranquility, safety and security at the expense of connectivity. They control traffic well but often create bottlenecks at peak times in predictable spots.
Street patterns can negatively affect the environment and neighbourhood quality of life. They impact the environment in that the street patterns consume land (up to 35 per cent of a district) and resources for their construction and ongoing maintenance. Local streets represent the bulk of the entire road network mileage of a region (over 70 per cent). They add to the impermeable surface area with a negative impact on water quality and contribute to urban heat that affects energy demand for cooling. Street patterns can impede or enable walking and bicycling thereby influencing energy use for transport. They can restrict or accommodate the flow of traffic thereby affecting GHG generation.
“Smart Growth” and neo-traditional community design
By the 1990s the problems of suburban sprawl were becoming evident and a new movement called “Smart Growth” evolved to promote the design of communities that are more compact, with a mix of land uses, well-connected streets and sidewalks, and public transit that would encourage a change in travel behaviour so that the residents would walk and bicycle more and drive less. In the search for more sustainable approaches, older neighbourhoods of cities - that were developed before the influence of cars - were identified as potential models of the mixed-use, walkable neighbourhoods to emulate. This approach, which borrows from the past to address a contemporary planning challenge, has come to be referred to as neo-traditional community design and is often based upon a grid street pattern.
Unfortunately, the neighbourhood street grid pattern – the inheritance of a pedestrian era - provides connectivity at the expense of tranquility and safety. In response, this grid pattern ushered in the era of traffic calming through use of speed bumps, traffic circles and stop signs which together impede traffic flow, increase automobile emissions and noise, reduce air quality and often lead to driver frustration. These grid street patterns are the most land consuming and consequently the least environmentally sustainable. CMHC-sponsored research identified that neither the grid street pattern nor the looping suburban street pattern were the optimum solution, and suggested a new hybrid of the two approaches, called the Fused Grid. (see figure 6-16).
The Fused Grid: A contemporary street pattern that addresses environmental and quality of life issues
Each of the existing street patterns (grids and loops) has positive attributes yet neither satisfies the entire set of environmental and quality of life criteria. An answer lies in their combination which is embodied in the Fused Grid. This uses a continuous grid of roads for district and regional connectivity and a discontinuous grid of streets for neighbourhood safety. The latter (neighbourhood) grid is supplemented by footpaths that connect all streets, turning a neighbourhood into a fully connected pedestrian realm (see Figures 6-16 and 6-17).
The combination of continuous and discontinuous street grids:
- Optimizes the use of land for streets
- Secures tranquil and safe neighbourhoods
- Increases the potential for social interaction
- Reduces the amount of impermeable surfaces
- Optimizes infrastructure
- Assists district and regional traffic flow
- Encourages walking while positively discouraging short-distance driving
- Provides opportunities for rainwater management.
In addition, the Fused Grid anticipates and channels land intensification and mixed-uses by creating a zone between residential districts that is flexible in possible land uses - which can include schools, parks and commercial. This zone can also accommodate adaptations to future traffic demand by allowing for road redesign and expansion within the existing road allowance.
The Fused Grid is a model for laying out neighbourhoods and districts. It combines the geometries of inner city grids and the cul-de-sac of the conventional suburbs. The objective is to retain the best characteristics of each and none of their disadvantages while raising the quality of the neighbourhood environment.
Applications of the Fused Grid
The Fused Grid can be applied as a neighbourhood or district model. Three area (large district) development plans have been approved by municipalities (Stratford, Ontario in 2003;11 Regina, Saskatchewan in 2006; and Fort McMurray, Alberta in 2007). In Calgary, Saddleton, a 64 hectare subdivision development plan, closely based on the Fused Grid (see Figure 6-18), has been submitted by the developer for approval by the city. This suburb design has open space to serve as:
- a space for recreation
- a pedestrian connector to all parts of the neighbourhoods
- a stormwater management system
- an opportunity for developers to increase density slightly.
A number of other municipalities are considering the application of the Fused Grid in partnership with CMHC.
Adopting street patterns that respond to current environmental concerns and the desire for improved quality of life offers a unique opportunity for the development industry to take the lead with a land use solution that is financially and environmentally sound.
The Fused Grid provides safe and healthy communities
The Fused Grid can influence the safety and health of communities in a number of ways. Street patterns can reduce or increase the risk of fatal accidents or injuries to people, particularly to children and seniors. Studies have shown that collisions are three times less likely to occur on streets designed with cul-de-sac and T intersections(see Figure 6-19) which are key elements in the Fused Grid road designs.
The Fused Grid street pattern can also help increase the level of tranquility in a neighbourhood and support social networking, which in turn reinforces a sense of security. It can reduce noise intrusion and improve local air quality by managing traffic. It can make walking and biking pleasant thus favoring an active healthy lifestyle. Finally, it can support the viability of amenities required for daily routines.
In summary, the Fused Grid balances the needs of the pedestrian and the motorist. It responds to the quest for economic efficiency and the need for environmental stewardship. It promotes active transportation which improves health and reduces vehicular travel and GHG emissions.