Sunday, August 31, 2008

Traffic Report

Cover of TrafficHere are my favorite parts from Tom Vanderbilt's book Traffic: Why We Drive the Way We Do (and What It Says About Us).

"The a place where many millions of us ... are thrown together ... There is no other place where so many people from different walks of life -- different ages, races, classes, religions, genders, political preferences, lifestyle choices, levels of psychological stability-- mingle so freely." (page 6) This reminded me of the snapshot of American life created by the collapse of the 35W bridge in Minneapolis last year: 13 people died, and as I noticed at the time, two were Somali (a mother and child), one Mexican, one Native American, two Asian, one a "classic Minnesota" Scandinavian, and six with names indicating various European ancestors. Of these, about half were male and half female, and one was developmentally disabled. You couldn't get a more representative example of the Twin Cities anywhere else, not even the State Fair.

The term "traffic" originally meant trade and the resulting movement of goods. Now, the primary usage we have related to that is "trafficking in stolen goods" or "drug traffic." And, of course, our primary concept of traffic has shifted to clogged roads that we would rather not be driving on. (page 7)

"We spend more on driving than on food or health care." (page 15)

Driving generally and highway driving in particular is set up to push our buttons. Humans are programmed to communicate, which involves looking at each other, while traffic makes us look at everyone else's back. "This muteness...makes us mad. We are desperate to say something." (page 24)

"...surveys have shown that most people [in the U.S.], given the choice, desire a minimum commute of at least twenty minutes. Drivers desire this solitary 'me time' -- to sing, to feel like a teenager again, to be temporarily free from the constricted roles of work and home." (page 26) That seems so crazy to me. They want to drive at least 20 minutes every day?

Driving is "the most dangerous thing most of us will ever do." (page 60) That sure puts it in perspective!

An insurance investigator from the 1930s named Heinrich found that for "every one fatality or major injury in the workplace, there were 29 minor injuries and 300 'near-miss' incidents that led to no injury... the key to avoiding the one event...lay in tackling the many small events..." This is now called Heinrich's Triangle, and it is being applied to driving as well as workplace accidents. (pages 63-64)

One of the coolest sections of the book tells about these researchers who put a Drive Cam into volunteers' cars. The camera is in there for a year, so after a few weeks, the driver basically forgets that it's there (as evidenced by much "nasal hygiene" captured on camera). The camera records all the accidents that almost happened, many of which the driver is never aware of -- the 300 incidents at the bottom of Heinrich's Triangle. (page 64) By using the feedback from their own driving, people who are caught on tape all became better, more attentive drivers, because the camera didn't let them forget or not realize the many times when they had driven unsafely.

Most "accidents" are not accidents in the true sense of the word -- the vast majority result from driver inattention or worse. The British Medical Journal no longer uses the term to refer to car crashes because most were not unpredictable, which is what the word accident implies. The term "accident" confuses the idea of unintentional with not predictable, which results in a true accident (page 66).

The more pedestrians or bicyclists there are on the streets, the safer they are per capita -- because drivers are less likely to hit something they are used to seeing. (page 86)

People talking on cell phones (whether hands-free or not) tend to fix their attention at a point just beyond the hood of the car, rather than shifting it frequently to cover the full view in front of (and inside of) the car. (page 88)

"Studies have shown that pedestrians think drivers can see them up to twice as far away as drivers actually do. According to one expert, if we were to drive at night in a way that ensured we could see every potential hazard in time to stop ... we would have to drive 20 miles per hour." (page 99) This reminds me of driving to my parents' rural home at night -- I think I was going at most 20 mph, knowing that there are a lot of deer at all times along the road.

Cities (before horse-based mass transit and cars) show a consistent pattern of being no more than 5 kilometers wide, so that a person could walk from anywhere in the city to the center of the city and back in one hour. We still maintain the same rule to this day, but instead of basing it on walking, we base it on driving. "Studies have shown that satisfaction with one's commute begins to drop off at around thirty minutes each way." (page 132)

In the 1950s, work accounted for 40 percent of daily car trips. Now, the figure is only 16 percent. The difference is made up by taking kids to school, child care, soccer, eating out... Average miles per American per day went from about 21 in 1960 to over 32 in 2001. And who is making most of those trips? Women, of course. And all of this "trip chaining" decreases the possibility of carpooling. (pages 135-136)

Only 15 percent of children walk to school now. "Parents on the 'school run' are thought to boost traffic on the roads by some 30 percent." (page 136)

"Each year, the amount of driving we do for shopping would take us across the country once and almost all the way back again." (page 137) As stores have gotten larger and farther from our houses (beyond that magic 1 hour walking rule), the number of people who would consider walking to the store plummeted. (page 138)

"...people tend to underestimate the time it will take to get somewhere in a car and overestimate the time it will take to walk somewhere." (page 144) People tend to think parking is too far away in core cities, but convenient in large parking lots at malls. This is because "people tend to overestimate distances on routes that are 'segmented,' versus those where the destination is in sight. Thus, a football stadium a half mile away in a big parking lot seems closer than a half-mile walk involving multiple turns in a city." (page 147)

Donald Shoup (author of The High Cost of Free Parking) found that on an average day near UCLA, cars in a 15-block area drove nearly 3,600 miles searching for a parking spot.

The bigger and more complex the intersection, the fewer cars per lane can get through it. A two-lane road can handle 625 vehicles per lane per hour each way. Adding a second lane in either direction allows another 483. A third results in 463. And a fourth, just 385. "The more you spend on new lanes, the smaller the return -- and the faster it becomes recongested." (page 163)

"Traffic congestion is a kind of two-way trap. Because driving is a bargain (drivers are not picking up the full tab for the consequences of their driving), it attracts many more people to roads that are not fully funded; this not only makes them crowded, it makes it hard to find revenue to build new ones." (page 164)

The "safer" the road in terms of engineering, the more dangerous it usually is because drivers' attention is not demanded to remain safe: "wider lanes, which are presumably safer, have been shown to increase speed and may encourage drivers to drive less cautiously." (page 185)

"A Florida study found that a pedestrian struck by a car moving 36 to 45 miles per hour was almost twice as likely to be killed than one struck by a car moving 31 to 35 miles per hour, and almost four times as likely as one struck by a car moving 26 to 30 miles per hour." (page 207) What a great argument for an enforced 25 mph speed limit in cities! (Minneapolis and St. Paul both use 30 mph as their base speed limit, with some streets higher. Many suburbs use a base of 35 and go up from there.)

Trees and other signs of livability in a community are seen as hazards by traffic engineers, but have actually been found to correlate with lower fatality rates compared to treeless, "safer" roads in the same community. (page 209)

"The longer pedestrians have to wait for a signal to cross, the more likely they are to cross against the signal. The jaywalking tipping point seems to be about thirty seconds (the same time, it turns out, after which cars waiting to make a left turn against traffic begin to accept shorter, more dangerous gaps)." (page 225)

"Studies have shown that the less densely populated a place, the higher the risk of traffic fatalities." (page 234) Interestingly, the higher the level of corruption in a country, the greater the fatality rate. (page 235) In the same way that increasing women's literacy rates decreases family size, decreasing corruption in a society may cause fatality rates to drop. (There's a lot more discussion in the book that clears up the possible confusion of correlation with causality.)

"If the number of deaths on the road were held to the acceptable-risk standards that the U.S. Occupational Safety and Health Administration maintains for service-industry fatalities ... there would be just under four thousand deaths a year; instead, the number is eleven times that." (page 250)

"In a crash at 50 miles per hour, you're fifteen times more likely to die than in a crash at 25 miles per hour -- not twice as likely, as you might innocently expect from the doubling of the speed... A crash when you're driving 35 miles per hour causes a third more frontal damage than one where you're doing 30 miles per hour." (page 252)

"... researchers found that SUV drivers were more likely to be talking on a cell phone than car drivers, more likely not to be wearing a seat belt, and -- no surprise -- more likely not to be wearing a seat belt while talking on a cell phone." (page 269)

Driving a new car means you are more likely to have a crash. (page 270)

That's a lot of facts all at once, I know. That's what reading the book was like, although Vanderbilt's full version flows a lot better! Definitely worth picking up a copy, and also checking out his How We Drive blog.

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