THE DANGERS OF SAFETY: Why Focusing on Car Accidents May Hurt Our Health

Everyone officially puts “safety first.” Everyone wants to prevent accidents. Car crashes are treated as lead stories on TV news – the images are horrific and we all fear our vulnerability. But, in fact, our roads are safer than ever. In 1956, when Interstate construction began, the national fatality rate was 6.05 per 100 million Vehicle Miles Traveled (VMT). By 2011, the fatality rate had dropped to 0.8 per 100 million VMT on the Interstate and 1.1 (the lowest ever recorded) nationwide, even though about 85% of people including those in metro areas, still get to work by car. (Massachusetts has the nation’s lowest fatality rate, 0.62!)

Studies have shown, and the Traffic Engineering Profession has internalized, that highway accidents go down when there are wide lanes, gentle curves, no sight-line obstructing hills, limited entering/exiting locations with long ramps, no visual distractions other than large and uniform directional signage, and the absence of slower or more vulnerable traffic.   The Interstate is safest when it is “error tolerant” and forgiving of driver distraction. (Other contributors along the same lines: slide-resistant pavement, break-away sign and light poles, and better guardrails.

But the reality is that safety lapses aren’t the biggest transportation-related source of injury. In fact, putting too much emphasis on preventing car crashes can make non-highway streets more dangerous – not only for pedestrians and cyclists but also for car occupants! Car accidents cause half as many deaths and several multiples fewer health problems than transportation-caused air, water, and noise pollution.   The amount of paved land in our cities makes us more vulnerable to climate change, rising temperatures, and floods while housing sprawl makes us less resilient in terms of agriculture and disaster-recovery.   Most subtly, life in and around automobiles changes the way we relate to our neighbors and friends, reducing our collective social capital and our individual life style satisfaction.


It’s easy to over generalize from actions appropriate for one context to other situations where they may actually have negative impacts: most of the strategies that make the Interstate safer for high-speed driving make daily city driving more dangerous. Unlike the Interstate, busy city streets become safer when drivers pay more attention to their surroundings, are unable to go fast, have to carefully negotiate turns, and are always made aware that the street and adjoining sidewalks are full of more vulnerable children, disabled, elderly, bicyclists, and shoppers who might step out at any unexpected moment and location.

The more that states and cities create urban “arterials” – local or regional collector roads typically “designed with the forgiving roadway features intended to enhance the safety of motorists” – the higher the accident rate.   According to a study published in the Journal of the American Planning Association, “each additional mile of arterial…was associated with a 9.8% increase in motorist crashes.”   Interstate-influenced local roads are also dangerous for people outside the car: higher vehicle speeds result in an increase in both the frequency and severity of crashes involving pedestrians.  The JAPA article states that “examinations of the spatial distribution of pedestrian-[injuring] crashes show that they cluster along urban arterials…”

Even beyond issues of speed, focusing on keeping car occupants uninjured can lead to road designs that increase the risk for pedestrians, bicyclists, and other non-motorized users. After declining between 2005 and 2009, the raw number of pedestrian deaths started climbing again, and in 2012 was back to essentially the same number as it was in 2003even though overall traffic fatality rates are down, according to SmartGrowth America. Nationally, pedestrians accounted for nearly 15% of all traffic deaths in 2013, up 6% from 2011 and representing a five-year high. (In the Boston area, pedestrians were almost 20% of traffic fatalities!) It’s no better for cyclists: in 2012, the last year for which full numbers are available, 726 cyclists lost their lives nationwide — almost two a day. (It’s far safer to fly. In that same year, there were zero fatalities from commercial airplane accidents in the United States.)

The hurt is not equally distributed: for African Americans, the age-adjusted pedestrian fatality rate was 60 percent higher than for whites. This is probably related to the racial tilt of our nation’s growing income inequality: lower income families are much more likely to live near major arterials and four-way intersections with traffic volumes 2.4 times greater than in high-income areas, according to a new study.


In addition, focusing on safety lets us ignore transportation-related environmental issues which have an even more powerful impact on the wellbeing we are seeking to improve: vehicular pollution injures many hundreds of thousands more people than car accidents and causes at least twice as many deaths. The National Highway Traffic Safety Administration says that the US is on track for an estimated 27,200 motor vehicle traffic fatalities in 2014, down nearly 6,000 over the past two years and down nearly 16,000 since 2005 (partly due to the long-term decline in VMT). In contrast, a recent MIT report found that “emissions from road transportation” cause 53,000 premature deaths a year.

It’s not just the deaths. According to a multi-year EPA study, people living, working, or going to school within 300 feet of a busy roadway – a disproportionate number of whom are low-income – are at increased risk of a huge variety of diseases: a 50% to 100% increase in annual mortality due to cardiovascular disease and cancer (particularly lung cancer even among non-smokers, although an association with breast cancer and childhood leukemia is also suspected), chronic asthma, possibly autism (up to a several hundred percent elevated risk associated with mother’s exposure during pregnancy or infant’s during first year of life), and possibly late-in-life decline in cognitive functions. There’s even an obesity connection: new research published in the journal Diabetologia found that “children growing up in areas exposed to high levels of traffic-related air pollutants had higher levels of insulin resistance, one precursor to diabetes.” Even people riding inside cars are exposed to about double the general atmospheric levels due to concentration from heaters and air conditioners.   And cyclists riding in traffic on the busiest roads get up to five times higher doses.

According to the American Lung Association, reducing air pollution has almost immediate, large-scale positive effects, with fewer deaths occurring within the first two years after reductions. “Looking at air quality in 545 counties in the U.S. between 2000 and 2007, researchers found that people had approximately four months added to their life expectancy on average due to cleaner air. Women and people who lived in urban and densely populated counties benefited the most.”

Diesel can be even worse than gasoline. The federal Occupational Safety and Health Administration has (finally!) officially stated that diesel fumes, to which about 12 million U.S. workers are regularly exposed, can cause dizziness and respiratory irritation after even short-term exposure and eventually raises the risk of both cardiovascular disease and lung cancer. Massachusetts is purchasing some new and cleaner diesel commuter rail locomotives which will replace half of those currently in service, but many of the dirty old ones remain and electric versions would require more investment than the state is willing to make.

Even more diffuse in its impact, and therefore difficult to study is the impact of noise pollution. The World Health Organization (WHO) has documented seven distinct types of negative health effects of noise pollution including hearing impairmenthypertensionischemic heart diseaseannoyance, and sleep disturbance. “In Norway, road traffic has been demonstrated to cause almost 80% of the noise annoyances reported…and passenger cars and lorries (trucks) are responsible for bulk of costs. Traffic noise alone is harming the health of almost every third person in the WHO European Region.”

Perhaps the biggest elephant is the effect of car travel on our national obesity rate. The risk of obesity increases 6% with every additional mile spent in the car, and decreases 5% with every kilometer walked, according to the Robert Wood Johnson Foundation


And safety keeps us focused on individual impacts rather than transportation’s longer-term, broader, societal impacts: the impact of our transportation system on long-term job growth, neighborhood livability, environmental sustainability, and interpersonal connections all of which strongly affect our quality of life, societal sustainability, and individual longevity.

Tire micro-shreds, combustion products, and de-icing materials damage streets and vehicles as well as surface and underground water supplies, and vegetation. Leaks from car-fuel-carrying boats, trains, and storage facilities affect coastal areas and aquifers.   Road construction both directly pollutes and creates “impervious surfaces [that] adversely affect water quality due to faster rates of runoff, lower groundwater recharge rates, and increased erosion.”

Covering our land with pavement also makes us more vulnerable to flooding and excessive heat. We’ve “artificially created flood-prone places simply by paving over the region’s natural ability to manage excess water,” points out Harriet Festing.   And “about 80% of the fuel that vehicles burn simply turns to heat,” according to Brian Stone Jr., director of the Urban Climate Lab at Georgia Tech, who adds that the replacement of tree cover with heat-storing asphalt results in cities heating up at double the rate of the overall planet, leading to greater air condition use with its own heat exhaust and energy demands. “In some cities, 20 to 25 percent of the total heat load is from engines,” he says.

Transportation represents 70% of US petroleum consumption, is by far the largest source of direct climate impact by US households and is also among the Massachusetts economic sectors which has shown the greatest inability to make progress with energy and climate mitigation. In Massachusetts, according to a Mass Audubon study the steady spread of housing, roads, and other development has left 22 percent of the Commonwealth’s land covered by asphalt, concrete, or other impermeable materials — up from 14 percent in 1981 — exacerbating the challenges of climate change.

LIVABILITY: The Quality of Life

According to a report in the Journal of the American Planning Association, “Transportation is the second largest expense for households in the United States, costing more than food, clothing, and health care. Low- and moderate-income households spend 42 percent of their total annual income on transportation…[nearly twice as much as] middle-income households…” But the real cost, and the real effect on our well-being, isn’t directly financial; it’s in the quality of our personal and social lives. Slate writer Annie Lowrey is simply articulating the common knowledge: “Long commutes cause obesity, neck pain, loneliness, divorce, stress, and insomnia.”

Nearly 50 years ago, Donald Appleyard found that people living on “lightly trafficked streets had two more neighborhood friends and twice as many acquaintances as those on the heavily trafficked streets….On the heavily trafficked street, respondents indicated that their apartment, or perhaps their building, qualified as ‘home.’ On the light-traffic streets, people often saw the whole block as ‘home’.”

Simply being in a car changes our perception of others. According to one study, participants who were asked to describe the character of others they saw from the perspective of looking through a simulated car windshield described them with more “negative characteristics (threatening, unpleasant)” than participants who were shown exactly the same video set up to feel that they were traveling by bicycle, foot, or transit. Participants in the non-car simulations described the people they saw as “higher on positive characteristics (considerate, well-educated).”

And, as usual, the impact isn’t equally distributed across our society. “Transportation projects should connect communities to opportunity, but too often new roads and rail lines have isolated low-income people and devastated the economic prospects of neighborhoods of color…[We need projects that] create jobs and business opportunities for residents, links low-income neighborhoods of color to employment centers, and strengthens local businesses along the route….[and confronts] the challenges of improving long-struggling neighborhoods without pricing out families and small local businesses….[promoting] economic inclusion for all aspects of the [project], from hiring and contracting to supporting small businesses during construction, to building affordable housing in long-struggling neighborhoods poised to rebound.”


Most dangerously, a narrow focus on moving-vehicle safety means that we come up with inadequate and unbalanced solutions. Yes, we need better vehicles (despite the auto industry’s endless predictions of economic disaster): safer, less polluting, more energy efficient. Yes, we need more advocacy movements like Mothers Against Drunk Driving, educational campaigns against distracted driving, tougher teenage-driver and elderly license-renewal regulations. But just as importantly, we need to radically change the way we design urban and “suburban town center” streets.

The most powerful impact on street-level reality comes from changes in our land use patterns. One survey showed that “the ten counties highest in ‘smart growth’ — i.e., compact and mixed forms of development — had less than a quarter the per capita traffic fatality rates than the ten with the most scattered and single-use growth patterns….”

If we can’t significantly reduce the need for cars, we can at least slow them down. “Engineers design streets for speeds well above the posted limit, so that speeding drivers will be safe—a practice that, of course, causes the very speeding it hopes to protect against.” Some 61.3 percent of pedestrian fatalities took place on roads with a speed limit of 40 mph or higher; only 9 percent of fatalities that occurred on roads with speed limits of less than 30 mph according to Smart Growth America. Instead of designing streets to be tolerant of speeding, we need to structure them so that it makes going fast difficult, if not impossible, as demanded by the “Twenty Is Plenty” campaigns in the UKNY, and elsewhere.

Simply narrowing roads through “road diets” that reduce the number of lanes from 4 to 3 (making room for larger sidewalks and bike facilities) and “lane diets” that narrow car lanes from the typical 12 to 15 down to 10 or even 9 can have a similar impact. According to one federal DOT analysis, “the combined estimate from all the best studies predicted that accidents would decline 29 percent, on average, after a four-to-three-lane road diet…” And the additional advantage of pavement reductions is that is frees up space for wider sidewalks and bike facilities.

Wider sidewalks and more bicycling facilities may be the quick and easy route to improved safety, especially for the nine out of ten trips that are not a commuting ride. As one recent publication summarized, “There is growing data showing that cities with very high use of bikes for routine transportation almost always have much lower than average traffic fatality rates…. Interestingly, the decrease in fatality occurred not just for people on bikes, but for all classes of road users — including people in cars and people on foot…” [probably related to lower speeds and greater driver attention.]

Beyond safety, there are other health-related benefits of moving away from car dependence. A Norwegian cost-benefit study on infrastructure investments concludes provisions for walking and cycling to be much more cost effective than traditional car infrastructure, the main positive component being positive health effects from walking and cycling. A study of the cycling city of Odense, Denmark, suggests significant public savings to be a result of local cycle promotion activities. The savings in public paid maintenance allowances for employees being off work for health reasons were found to be bigger than the total investments in campaigns and infrastructure.

Road designers are constantly looking for people taming devices so that cars can be safe to drive fast. What we really need is traffic taming so that people are safe – and our society is healthy.


Thanks to Wig Zamore whose always knowledgeable comments prompted this topic.


Related previous blogs:

TIME TO GET SERIOUS ABOUT SAFETY: Looking Beyond Traffic Lights


VULNERABLE ROAD USERS (VRU) PROTECTION LAWS: “Whoever Can Do The Most Damage Has To Be The Most Careful”

Broken Windows and Broken Streets – Livable Streets as a Strategy to Reduce Crime and Support Local Business

BICYCLING SAFETY: Preventing Injury Requires Multiple Strategies

DANGER FROM BELOW: Our Leaky Gas Pipe Infrastructure


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