Want to Slim Down L.A.’s Children? Plan Streets for Less Cars

UC Berkeley professor Michael Jerrett strongly suggests in a new study that reducing the traffic near people’s homes could have a dramatic impact on the health of the children living near public streets.

The bad news?  Obesity rates for children in Los Angeles is high.  For example, a recent study by the California Food Policy Advocates showed that just over thirty-five percent of seventh graders in Los Angeles have an "unhealthy weight" and forty-two percent have an unhealthy aerobic capacity.  As you might expect, unhealthy kids are an indicator of unhealthy adults.  The CAFPA study shows that over fifty percent of L.A. County adults fall into the "unhealthy weight" and "unhealthy aerobic capacity" categories.  All of these statistics are well above the national average.

Both NYC Streetsblog and SF Streetsblog have taken a look at the report, and broken it down.

In NYC, Noah Kazis reports on the study, which links traffic volumes to youth obesity:

Jerrett shows that not only does the built environment matter, but
traffic volumes matter too. His team’s long-term study tracked children
from across Southern California, starting from ages 9-10 and continuing
through high school. Controlling for a wide variety of factors, they
compared the children’s body mass indexes (BMI) to the density of
traffic near their homes.

Children living within 150 meters of high-traffic areas were
found to have, on average, BMIs five percent higher than those living
near low-traffic areas. Only the immediate surroundings seem to matter:
Traffic levels within 300 or 500 meters didn’t affect BMI.

Michael Rhodes, in San Francisco, continues

The researchers put forward two reasons for why traffic volumes
contribute to obesity. High asthma rates could be part of the equation,
making kids less likely to engage in physical activity. Kids – and
their parents – also seem to be especially sensitive to the real or
perceived danger from cars, much more so than adults.

So what can be done?  Jerret sees the ultimate solution to be less cars in sensitive areas, i.e. places where people should be open to walking or biking for transportation and places where children live.  He uses the example of London’s congestion charging, which reduced traffic by 18% in the central city. 

Unfortunately for Angelenos, he takes a somewhat dim view that mixed use neighborhoods are a complete solution if traffic persists.

Moreover, solutions posited in existing literature on built
environments suggest that connected, mixed land use neighborhoods with
good “walkability” to destinations in proximity to the home may provide
some protection against obesity and physical inactivity. If traffic is
an independent risk factor, however, improving the physical structure
of the city may be ineffective if high levels of traffic persist in
residential neighborhoods.

That means that we can do all the planning and encouraging of cleaner lifestyles that we want, but if we’re unsuccessful in reducing the number of cars on our streets, than we’re going to be fighting a losing battle against obesity.  That’s just one thing to consider the next time a traffic engineer proposes widening a street for "safety and efficiency" reasons.  They may be encouraging more cars to drive on the street, but any perceived safety benefits should be weighed against the damage being done to the health and fitness of our children.

  • Ms. Stephanie

    Seems like somewhat of a specious connection. Did anyone look at the incomes of the families who live near intersections with high traffic volumes versus those who live near intersections with low traffic volumes? I wouldn’t be terribly surprised if there was an income difference – i.e., families with lower incomes live near the higher traffic intersections. And as we all know, in our completely f-ed up food economy, it’s cheaper to buy the family a bunch of Big Macs than healthy food from the grocery store.

    Don’t get me wrong, as a cyclist myself I’m all about increasing the number of bikes on the street and decreasing traffic volumes, but I feel like the connection in the study may be ignoring other explanations. (Granted, I haven’t read the study myself…)

  • Chewie

    Cleaner cars seem to be helpful here, since they would contribute less to asthma. It’s really frustrating though. It’s very hard to get people to walk to anything without mixing land uses, yet that very mixture requires density (also necessary for financially sustainable frequent transit service) which often adds to traffic. Seems like damned if you do, damned if you don’t.

    Why don’t we put more speed bumps on residential streets to frustrate cars, and tax gasoline a lot so people buy cleaner cars and/or use cars less? Health of children vs. easy driving. I wonder what will win.

  • A great post ruined by two comments I don’t agree with.

  • Ms. Stephanie,
    Interesting point about income and obesity, that link has already been much discussed in other places but isn’t really brought up in this report that I can tell.

    However, a lot of the argument has to do with incorporating excercise and outdoor time in people’s lives. Given the barriers we’ve created to walking and biking to school, in large part to accommodate auto vehicle travel, it’s hard not to notice what we’re doing to our kids by building the way we are.

  • Gokhan

    Banning soda machines in schools by Arnold was a good move — a fringe benefit of having a governor who is a former fitness specialist. Sodas should also be banned at home. Parents who are buying their kids soda drinks are poisioning them with sugar.

  • Ms. Stephanie:

    It appears the researchers controlled for a large number of socioeconomic factors, including income, crime rates, asthma, food availability, local greenspace, and household tobacco use. So while it’s a reasonable concern, it appears they’ve treated traffic impact independently and still found a significant correlation.

    I suspect that some of those other factors may have even larger correlations, but that doesn’t discount the significance of the findings.

  • Gokhan

    I think the biggest problem is the childhood obesity. More educated families tend to provide healthier nutrition to their kids by limiting junk food and drinks and they make sure that they get enough exercise. Walking as opposed to riding a car always helps to stay slim and muscular but diet comes first. You are what you eat. And the foundations of obesity are cast when you are a child. I think walking promotes strong muscles and joints but it wouldn’t be enough to burn the excess calories of malnutrition, which leads to childhood obesity and then lifelong obesity and diseas like diabetes and heart diseases.

    In a way obesity is the disease of the capitalist society, where widespread lack of education and heavy advertisement by junk-food-and-drink companies, combined with the oblivious ways of capitalist living, leads to oblivious ways of food and drink consumption — only a part of our ill society.

  • Chewie

    I dunno Gokhan, Mao Zedong was kind of chubby, despite his fierce opposition to capitalism :)

    You can eliminate traffic near you by moving out to a rural area. But then you probably have to drive everywhere (so ironic). But I guess you could run laps in your yard, or work in the fields, or bike 20 miles to the nearest store to slim down.

  • Great post and comments – it’s exciting to read this study. As some of you might know I recently started working for the National Safe Routes to School Partnership – my work is focused on policy at the Regional level (SCAG region) – as well as across the state of CA. The link between public health and mobilty/accessiblity is huge. I’m just getting started in my new role but happy to discuss further and be a resource if I can be – don’t hesitate to email at jessica(at)saferoutespartnership.org

  • Jessica,

    The streets next to Lincoln Park in Lincoln Heights, and around Lincoln High School are atrocious for pedestrians. What can I do to slow down car traffic, improve the sidewalks, and make the area safer?



    p.s. Along with high ashtma rates, we also suffer from a lot of childhood obesity problems in this area.

  • I wonder if wide spread use of bicycle boulevards would help the
    situation? I know that shared lane markings alone won’t do it.



  • Ubrayj02 – I’ve been learning about legislation adopted in 2008 AB 321. This allows cities to voluntarily adopt this policy which will extend school zones by 1,000 ft and restrict speed limits to 15mph – when they are usually 25mph. This is a great thing to look at for the City of LA. There are certain qualifying factors for the school – on what is defined as a residential street and existing speeds no more than 30mph. I’m learning more about this policy – it seems like a great idea for cities to consider/adopt where it’s possible

    Also – what about if your community formed a neighborhood Safe Routes to Schools Task Force? Consisting of parents, students, community members, public health professionals, Law enforcement, principal of the school – this has been effective in other communities in developing strategies.

    There are cities here in So Cal that have been able to address improving the bike/ped safety and connections around their school – as I learn more how they did it, will pass along.


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