Passing the Safety Test
The fused grid network pattern recently 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.
For more information on the research project
To find out more details about the Traffic Safety Analysis, contact James Sun at UBC:James.Sun@ubc.ca
Fused Grid Explained
The “Fused Grid” is a neighbourhood and district layout model that was developed by Fanis Grammenos, a senior researcher at Canada Mortgage and Housing Corporation. “It combines the geometries of inner city grids and of the conventional suburbs,” explains Fanis. “This fusion results in retaining the best characteristics of each and none of their disadvantages while raising the quality of the neighbourhood environment.”
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:
- Fused Grid can turn a neighbourhood into a fully connected realm and help create a healthy community
- Greening the Grid – Low Impact, Fused Grid development in Calgary
- A Plan for Rainy Days: Water Runoff and Site Planning
- The Fused Grid: A contemporary street pattern that addresses environmental and quality of life issues.
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
A decade 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”
Posted April 2009