California is full of prime infill development locations, but it’s also full of freeways. And more often than not, the two go together. Decades ago, the freeway system was built through existing urban areas and emerging suburban areas. Today, the old commercial strips next to the freeways have a lot of underutilized land, including surface parking lots. These are frequently the areas that have been targeted for infill development – usually either condominium projects or mixed-use with residential and retail.

Now a new study from the Institute of Preventive Medicine at the University of Southern California suggests that this is not a great idea for the residents themselves – especially if they are children. The study, published in The Lancet ( in January, found that children in the Los Angeles area who live within 500 meters of a freeway (about 550 yards) have diminished lung capacity compared with children who live more than 1,500 meters away from a freeway (about a mile). The study’s authors (there are no less than 11 of them) warned, in particular, that an expected threefold increase in truck traffic over the next 20 years holds the potential to increase greatly the risk of lung problems in children who live near freeways.

The study has generated a lot of publicity in urban planning circles, especially in California, and it has begun to call into question the common strategy of putting infill development close to the freeways in urban areas. At the very least, advocates of low-density greenfield development are likely to use the study to promote their cause. Yet, given land constraints and traffic congestion – especially in Southern California – further infill development near freeways seems inevitable if not common.

Actually, the study’s conclusions don’t address the question of whether or not to locate residences near freeways. Rather, they focus on possible changes in policies to reduce air pollution. The study’s authors concluded that “staying even” by reducing emissions enough to offset additional traffic – the trend of the last 30 years – won’t be enough to protect children’s health. We will have to come up with ways to create a net reduction in emissions even if traffic continues to increase, which seems inevitable.

The authors also focus on the question of residences located close to freeways in poor neighborhoods, and policies that might deal with that issue. While acknowledging that all children who live close to freeways are at risk, the researchers emphasized that the “double whammy” of living freeway-close in a poor neighborhood – which is more likely to have air pollutants in the first place – places poor kids particularly at risk. The authors suggest that air pollution laws might need to be changed to put greater focus on local hot spots as well as a reduction in regional emissions.

From a planning perspective, classic McHargian geographical analysis would suggest that we simply place areas near freeways off-limits for residences from now on. (That’s assuming the research results are for real, which they probably are.) But can planners really put all other considerations aside in order to protect this one aspect of public health?

Even as planners are beginning to consider issues of public health, they are still under tremendous pressure – especially from housing element law – to identify locations for high-density housing and make it easier for such projects to get built. This is especially true in both L.A. and the Bay Area, where many cities are smaller, older, mostly built-out suburbs near freeways.

Planners in greenfield cities are used to this kind of bind – having to meet environmental goals (such as protecting endangered species) imposed by the state and federal governments while at the same time having to meet state-mandated housing goals. But at least those greenfield cities have the option – admittedly unpopular politically – of creating higher-density projects in those locations not knocked out by environmental regulations. Older suburbs don’t have this alternative. Most of their available land is already slated for high-density development and most is close to freeways.

Beyond that, the implicit environmental justice concern undercuts one of infill development’s most compelling policy arguments, which is about environmental quality. Dense infill may create local traffic congestion, but it reduces overall regional vehicle miles traveled and therefore improves regional air quality. But what if regional air quality matters less than we think, and local air quality matters more? Then infill looks less attractive.

The more you think about this issue from a planner’s perspective, the more it looks like a classic conflict between regional benefits and local impacts. For decades, planners have dealt with the question of how to deal with landfills or nuclear power plants – noxious or high-risk facilities that provide a regional benefit thinly spread across the entire population but have a potentially devastating impact on neighbors. Usually, the rationale for building such facilities is that the regional benefit trumps the local impact.

Is it possible that freeway-close infill serves the same purpose? We need more housing and there aren’t many places to put it except near freeways. We need to reduce overall emissions; dense infill development is a necessary part of the fix. We need to build more housing near transit, but most new transit is being built along existing transportation corridors, and mostly these are freeways and existing rail lines (which also carry a lot of freight traffic). It makes no sense to locate dense development far away from these corridors.

These are pretty compelling arguments for infilling freeway-close locations – you can picture the statement of overriding consideration language in the environmental impact report – except for one thing: In this case, the offending project isn’t a power plant or a prison. It’s a residential development that is actually housing the very people whose health is supposed to be protected by public policy.

Are planners really going to make decisions about how close to a freeway somebody can live? This is definitely a judgment call involving the kind of risk-benefit analysis that public health officials are used to dealing with but planners are not. The headlines all suggested that we shouldn’t let people live within 500 meters of a freeway. But the research team didn’t analyze all possible distances and determine that 500 meters was safe. Rather, the researchers picked four different buffers – 0-500 meters, 500-1000 meters, 1000-1500 meters, and more than 1500 meters – and examined the lung condition of children in each zone. It’s clear that further away is safer. But it’s not clear how far away is safe enough.

Of course, the real problem here is not that the houses are close to the freeways, but that transportation fuels of all kinds are among the biggest polluters in our world. We’re gradually switching to cleaner-burning fuels and many policy initiatives at the federal and state level are pushing us even faster on that front (see CP&DR Insight, February 2007). Will living near a freeway present the same kind of risk 20 years from now as today? That all depends on how quickly we switch fuels.

In the meantime, though, planners are placed in the tough position of making the kinds of judgments about human health that are typically the purview of public health officials.

In the rarified world of state or federal policymaking, these kinds of judgments are made all the time by public health officials and are not subject to much grassroots scrutiny. There are no local town hall meetings about the acceptable health risks of a new product or fuel. In the emotion-laden world of local land use decision-making, these kinds of risk-benefit judgments become much tougher. It will be very difficult for planners and local officials to argue successfully that, on balance, we should take a risk because society is better off if we put some kids into infill housing near freeways.