Now I say self proclaimed as many of these folk have no formal qualifications related to urban planning but still feel they are they authority to tell others how the city should be. I'll admit that I'm not an urban planner either, however I do have many years of experience of designing transport infrastructure.
So back to today's myth:
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| Cul-de-sac |
"Cul-de-sac's promote auto-dependency and make walking and cycling non-viable options of transport"
Background:
The background to this myth is that cul-de-sac's happens to appear in many auto-dependant suburban subdivisions that have been built in many places all over the world and so by coexistence have been accredited with the poor planning behind the subdivision as a whole.
The real issue here is that we have gone through a period of time where cities have grown under strict zoning laws that have prevented mixed use developments and have focused on building large swaths of residential land which is completely disconnected from commercial, industrial and municipal area and hence resulting in long journeys.
The Reality:
Although the cul-de-sac is accredited with promoting auto-mobile use, obesity and the decline of walking and cycling the reality is it does the complete opposite.
In the following image you can see the standard grid layout, what you will note is that it is rather dense and efficient being able to serve a large number of properties with a minimal number of roads.
The downside of this layout however is that you will get large amounts of traffic heading along every road. Due to every road being busy there will be significant disruption at every intersection as there will be no primary movement to take priority. There are no benefits from using one mode in comparison to another when you are looking at the distance needed to be travelled, you also wont find some routes that are more suited for pedestrians and cyclists and other more suited for cars and trucks.
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| The Grid - Hamilton |
Looking at the more modern suburban layout I have the following image which is from an area of Hamilton developed in the 70s & 80s.
What you will notice here is that the road network has changed so that we now have semi-direct main roads and then various local roads that comprise of loops or cul-de-sac's. What this does is funnel the traffic onto the larger main roads leaving the local ones for the few people who live on them as opposed to the grid that had everyone driving along every road. So in the modern case the arterial road will likely have more traffic than any individual road in the grid layout, the majority of roads will actually have less traffic. In the case of the cul-de-sac it will have such a low amount of traffic you could happily let your kids learn to ride a bike out on the road when you wouldn't dream of doing such a thing on a grid road network.
The other benefit we have is that these developments tend to be focused around a community shopping centre or park, and when you look at the road network you will find the distance you need to walk or cycle to these places is significantly less than the distance you would need to drive due to various short-cuts being provided. In some cases you may only need to walk about 500m to get to the shops, whereas if you drove it could be as much as 2km. This also helps when it comes to running public transport services as the various short cuts give pedestrians easy access to the main road where the service would be running.
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| 70s & 80s - Hamilton |
Comparison:
So when you compare the two different layouts we find the following:
Grids:
- Every road is busy
- Travel distance the same for all modes of transport
Cul-de-sac's
- Busy main roads
- Quiet side streets
- Short journeys when walking or cycling
- Driving not effective for short drips
