Someone asked me recently to explain why the Planning Commission “doesn’t like culs-de-sacs”. I have a fondness for culs-de-sac and used to live on one, but they do have some serious shortcomings which, to me, outweigh their pleasant aspect. I was interested to read some new research that clearly quantifies ways in which our American suburban street model, which so dominated the second half of the 20th century, is in fact more dangerous than the traditional grid. (continued)
The newer cities tend to have more “dendritic” networks — branching, tree-like organizations that include many cul-de-sacs, limiting the movement of traffic through residential areas. They also don’t have as many intersections. The pre-1950 cities, on the other hand, tend to be more grid-like, giving motorists many more routes to choose from.
The ASCE study also concluded that street networks containing many cul-de-sacs increased travel demand on arterial roads by 75 percent and on collector roads by 80 percent, compared to a gridded street design. That, too, may help explain the higher fatality rate associated with the street networks that became prevalent after 1950.
You can read the original article here, then come back to comment.
As background, the Project for Public Spaces website has an excellent overview of some of the changes that are happening in the field of transportation planning (they call it a “revolution”), which shows how we got here and what we can do to reverse some of the damage.
What do you think? Are the arguments compelling, or not?