FLASHBACK TO 2009: “The Fused Grid combines the geometries of inner city grids and of the conventional suburbs.” stated Fanis Grammenos

Fused Grid Explained

The “Fused Grid” is a neighbourhood and district layout model. It combines the geometries of inner city grids and of the conventional suburbs. This fusion results in retaining the best characteristics of each and none of their disadvantages while raising the quality of the neighbourhood environment.

Fanis gammenos (180p)The planning model was developed by Fanis Grammenos, formerly a senior researcher at the CMHC in Ottawa, and a team of colleagues. It combines two traditional street designs: the conventional loop and cul-de-sac pattern of the modern suburb and the grid pattern from the early 1900s.

According to Grammenos, “The traditional grid pattern provided efficient routes and “connectivity” for pedestrians and those travelling by horse and buggy. The loop and cul-de-sac pattern reduces the impact of traffic on a community.” Through his research, Grammenos discovered that residents want the best of both street patterns. In particular, they want connectivity, safety and the tranquility of quiet spaces.

“It was apparent that these qualities needed to be established in a new pattern, because the old pattern would not deliver the new qualities,” Grammenos says. He also found in examining market research and buying patterns that people prefer quiet neighbourhoods without through streets.

“People have consistently paid more money for houses located at the top of a cul-de-sac, near a ravine, facing a golf course or having a view of a lake,” Grammenos says. “Generally, people have paid more money willingly to have a view of nature and be as quiet as is feasible in the environment that they choose to live in.”

The fused grid is inspired by a theme — the common space — from an 18th-century plan of Savannah, Georgia. “The city plan is organized in repeatable wards, with a square in the centre, which is visible to half of the homes in each ward”, explains Grammenos, “The square is protected from heavy traffic since through streets are located at the boundaries of the ward, leaving the centre relatively calm for casual strollers.”

Passing the Safety Test

In 2009, the fused grid network pattern passed another test with top marks – the traffic safety test. Planners using it for its rainwater management advantages can now be confident that it will also enhance safety.

A research team at the University of British Columbia (UBC) consisting of Dr. Gordon Lovegrove and James Sun did extensive modeling of five network patterns to compare their propensity for reducing collisions.

Why We Need to Reduce Traffic Collisions

According to the researchers, collisions stack up enormous social and personal costs in the range of 25 billion dollars a year in medical and insurance bills apart from the personal suffering caused by injuries. In addition, the perception of risk, that intensifies with each reported or witnessed accident, reduces the odds of people choosing to walk or bike, thus removing the opportunity for modest but therapeutic exercise. In this light, any reductions in collisions are welcome and the greater the reduction the better.

Application of Collision Prediction Modeling

Previous sporadic or anecdotal evidence had pointed to specific elements of street configurations as being safer, such three-way intersections for example. But this study for the first time put existing and proposed whole network patterns through the rigour of innovative computer modeling called CPM (Collision Prediction Modeling) to test their potential for reducing collisions. Five patterns were tested that are named in the chart below.

The results show that the Fused Grid, along with the 3-Way Offset pattern, performs much better than other current models.

The differences are substantial, particularly with the common traditional grid, which is found in most city central areas. The common grid is 2.5 times more prone to produce collisions than the Fused Grid.

Integration with Rainwater Management

From the point of view of managing rainwater, the bad news is that the traditional grid is also the pattern that inherently produces the highest impermeable surface ratio in developing new neighbourhoods. Replacing it with the fused grid will achieve two goals with one move: increase permeability and reduce collisions.

Add to these two advantages the fact that walking is made more pleasant and convenient, and it becomes hard not to consider the fused grid as an option in the development of new neighbourhoods.

Previous Stories Published on the Water Bucket

To learn more about the Fused Grid and the work of Fanis Grammenos, please click on this link to The Fused Grid: A Contemporary Urban Pattern; as well as these links to stories posted on the Water Bucket website:

The Fused Grid is increasingly attracting attention within the planning community – for example, the Fall 2008 issue of the Planning Commissioner’s Journal, a print and e-zine includes an article on the Fused Grid.

Learning from the Experience of Others

Two decades ago, the City of Surrey in British Columbia pioneered alternative development standards in the East Clayton Sustainable Community. “The City and others certainly learned a lot from the East Clayton experience,” stated Remi Dubé, the City’s Drainage Planning Manager at the Surrey Water Balance Model Forum in March 2009.

“In addition to design and construction issues, the City also learned some lessons from a site development perspective. An unintended consequence was the higher than expected percentage of hardscape. With a different approach to built-form, we could have had both higher density and substantially more green space.”

This is illustrated by the following comparison. On the left is what East Clayton looks like; on the right is what it might have been. For the complete story, click on Green Infrastructure in the City of Surrey: “Getting it built right”