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QuoteSome of the most trusted planning tools used to manage vehicular traffic have shown themselves to be pretty harmful to city life in certain ways. A metric known as Level of Service, which aims to minimize automobile delay at an intersection, can act as a huge obstacle to public transportation projects. A design book calling for 12-foot lanes, an engineering staple across the country, can speed up car flows and endanger public safety as a result.
It might be time to add one more established tool to the questionable list: the Trip Generation Manual from the Institute for Transportation Engineers, a common guide that tells traffic planners how many car trips will be generated by a new commercial or residential development project.
That's the argument made by environmental scholar Adam Millard-Ball of UC-Santa Cruz, who challenges the merits of the Trip Generation Manual in an upcoming research paper (nicely summarized in ACCESS magazine). Millard-Ball reports that the ITE manual may overestimate the number of trips generated from a new development by as much as 55 percent—"phantom trips," he calls them. The result is that cities may build way more roads than necessary, perpetuating sprawl and leaving less street space for non-drivers in the process.
"[The ITE manual] is used pretty much everywhere for small or medium-sized development," Millard-Ball tells CityLab. "In some places it's a starting point rather than a final word, though I think that's still pretty rare."
Full article: http://www.citylab.com/cityfixer/2014/12/a-widely-used-planning-manual-tends-to-recommend-building-far-more-roads-than-needed/383759/