Traffic impact studies that underpin land-use policies in California are akin to junk science, overstate resulting vehicle traffic patterns and consistently drive up the price of housing in a state where homelessness is a potent political issue, according to land-use analysts.
Those are some of the recent conclusions by land-use analysts who say that current traffic impact analysis methods amount to only “embedded assumptions” and do not meet the standard of review courts use to assess expert witnesses.
“It’s actually one of the bigger scandals in American land use,” said Matt Lewis, director of communications for California Yimby, a nonprofit group that advocates for affordable, abundant housing.
Current traffic analyses tend to focus only on vehicle trips resulting from new developments, often leading to requirements on developers to pony up funds for street widening to accommodate future vehicle traffic and more parking facilities. Such directives from local land-use officials can increase the costs of individual condo units in housing developments by $60,000 to $120,000, according to Lewis.
“Every penny of that cost gets rolled into the cost per unit,” he told the Southern California Record.
Different California communities have used different formulas to price parking into the cost of housing developments, according to Lewis, but the city of Costa Mesa at one point assumed that a single condo creates the need to factor in four additional cars.
“It was just received wisdom,” he said. “(It assumed) the traffic engineers know what they’re talking about. … It was junk science.”
Flawed traffic studies often focus only on potential changes to vehicle trip patterns and ignore key issues such as proximity to mass transit and busways and proximity to day care facilities, restaurants and shopping areas, according to Lewis.
In California, disputes over new housing developments often lead to long court battles.
Although critics of the Institute of Transportation Engineers (ITE) trip estimation methods say traffic engineering studies are rarely challenged in court, judges are beginning to take a more critical look at the studies, according to a recent American Planning Association post.
“Some courts are starting to question the validity of incomplete ITE data as agencies and practitioners around the country adopt innovations,” the post authored by Adin Becker states. “For instance, the Washington State Supreme Court rejected a TIA because it presented no local data to the Bellevue City Council. While this is the first case of a court rejecting the ITE method, this development signals that stricter standards for TIAs may be on the horizon.”
Current traffic analyses are often biased toward trends in suburban areas and national averages, exaggerate vehicle-based rates and are outdated, the blog post states. But cities such as Los Angeles and New York in recent years have been working to accumulate localized data that is more relevant to traffic prediction, according to the post.
An article by California Nimby published last year urges courts to view traffic analyses with greater scrutiny, in particular cases where such analyses lead to costly infrastructure improvements. Modeling for such studies is based on small sample sizes, old assumptions and contexts that are at odds with local conditions, the report states.
Municipalities and other local agencies may also struggle to fund ongoing road maintenance, so they may be inclined to call on developers to fund more infrastructure improvements than developments merit, according to Strong Towns, a nonprofit advocacy organization. In turn, there’s more focus on making cities accommodate more cars rather than traffic-mitigation measures that ultimately improve the quality of life in urban areas, traffic study critics say.