- For the citizen planner:
Here's a link to the "Community Guide to Development Impact Analysis", by
Mary Edwards. This is a workbook which provides an overview of some of the
various issues of concern to local officials regarding conventional
development. Much of this, of course, would apply to a carfree project as
From the Traffic Impact Analysis chapter:
"...Traffic impact studies should accompany developments which have the
potential to impact the transportation network. They are important in
assisting public agencies in making land use decisions. These studies can
be used to help evaluate whether the development is appropriate for a site
and what type of transportation improvements may be necessary.
Traffic impact studies help communities to:
· Forecast additional traffic associated with new development, based
on accepted practices.
· Determine the improvements that are necessary to accommodate the
· Assist communities in land use decision making.
· Assist in allocating scarce resources to areas which need improvements
· Identify potential problems with the proposed development which may
influence the developers decision to pursue it.
· Allow the community to assess the impacts that a proposed
development may have.
· Help to ensure safe and reasonable traffic conditions on streets
after the development is complete.
· Reduce the negative impacts created by developments by helping to
ensure that the transportation network can accommodate the development.
· Provide direction to community decision makers and developers of
· Protect the substantial community investment in the street system.
In a section on estimating trip generation, there is a brief mention of
"capture rate"---a percentage reduction in traditionally developed trip
forecasts to account for internal trips in a multi-use development: "The
Institute of Traffic Engineers has found that multi-use developments could
reduce trip generation estimates by 24%".
It would be interesting to find out how they come up with these numbers,
and to try and generate related figures for carfree projects in various
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