UCLA Institute of Transportation Studies

Traffic impact analyses (TIA) are widely used by local governments to assess the traffic impacts of proposed land use developments. TIAs are often measured in terms of expected changes to traffic flows through nearby intersections using a metric called “level of service” (LOS). This process tends to be biased against higher-density developments in urban areas where traffic is already congested and travel alternatives are plentiful. Researchers have found that the projected traffic impacts of developments in already built-up areas tend to be overestimated, which leads to higher traffic impact fees and related costs associated with the TIA process. Often, local residents use such analyses as evidence to oppose new developments on traffic grounds. The result is that TIAs can help discourage new housing production in built-up areas where demand is greatest, which likely exacerbates the housing affordability crises in places like California.