It’s not what you drive, but how

Kai Ryssdal Aug 26, 2008

It’s not what you drive, but how

Kai Ryssdal Aug 26, 2008


KAI RYSSDAL: I’m kind of hoping you’re tuning in in the car on the way home. Because what you’re about to hear might explain a lot of what’s going on around you.

The guy in the next lane who’s not merging even though there’s clearly a lane closed ahead. Or why traffic lights never seem to be lined up green in the direction you’re going.

The thing to remember is that when you’re on the road it’s not about really about you the single driver. It’s about the rest of us. That’s one of the points Tom Vanderbilt makes in his new book, “Traffic.”

Tom, good to have you with us.

TOM VANDERBILT: Great to be here.

KAI RYSSDAL: The thought that was going through my mind the whole time I was reading this book was, “Man, he can’t be talking about me. I’m a great driver.” And I bet everybody else had the same thought, right?

VANDERBILT: Yeah, you know, studies show that 90 percent of us, when these surveys are done, say they are an average or better-than-average driver. Which, I didn’t go to M.I.T. or anything, but mathematically sounds a little bit dodgy.

RYSSDAL: Well, it’s tricky, right? Because basically what I want when I drive is to get where I’m going as fast as I can in one piece. But that is not always, you say, the best thing for everybody else on the road.

VANDERBILT: Even in congestion and jams, you’re often finding large groups of drivers just driving into those jams at pretty high speeds, which leads to not only rear-end crashes but sort of worsens the jams. And there’s a thought that if you could just make drivers approach at a slower, steadier pace, it would be quicker to get out of that congestion. And so, in England, on the M-25 motorway, for example, they have something called variable speed limits, which the computer sensors are alerted that there is a jam developing and a new speed limit is sent back, upstream — as the engineers call it — for the drivers to respond to. So, it’s a slower and steadier approach, rather than just basically driving into a big pack of congestion.

RYSSDAL: One of the points you make, Tom, is that driving, you know, for as utilitarian as it is, it’s just flat hard, right?

VANDERBILT: In one study they found that driving at 30 mph you were exposed to 1,300 pieces of information per minute. So, driving is incredibly complicated, and we find ways to sort of make it moreso by introducing texting and cell phones into our cars when — if you really think about the actual act of driving — it’s quite intensive.

RYSSDAL: So here’s the question I bet everybody is going to want to know the answer to out of this interview, which is, Why is it that there will be a fender-bender and it takes the traffic from that minor incident an hour-and-a-half to clear?

VANDERBILT: Engineers have various rules of thumb on this but . . . things like one minute of an incident will create four minutes of congestion. And if you think about traffic as sort of water flowing into a bucket — and imagine there’s a hole at the bottom of that bucket that’s a certain size — that’s your bottleneck. You might sort of widen that bottleneck over time but it’s still going to take a while for all that water to drain out. And you’re still adding new water, so you’re either sort of driving into the back of that jam as it’s dissipating or the jam’s growing toward you. And, you know, when a two-lane highway has one lane blocked, that’s a 50 percent reduction in capacity.

RYSSDAL: So, why do we drive the way we do?

VANDERBILT: Well, you know, we are all individuals. We have our own view through that windshield that kind of warps our perspective, I think. And it’s hard for us to imagine the traffic system as a whole and engineers sometimes have to work with technologies and strategies to fight our individual impulses. Like, in Los Angeles, for example, the classic case is ramp meters, those little traffic lights at the end of on-ramps that keep you from going on when it looks like the highway is moving fine. So, people are wondering, “Why are you not letting me on the highway? It’s flowing fine.” And the engineers say, “The reason it’s flowing fine is because we’re not letting you on the highway.” Just that tension between the individual and the system — and what’s good for one is not often good for the other.

RYSSDAL: Well, what do the traffic engineers tell you when you go and chit-chat with them and spend time with them? Do they know that they’re banging their head against the wall and they’re dealing with a crafty, crafty enemy in the American driver who’s going to find a way around whatever they decide to do?

VANDERBILT: Undoubtedly. The best example of this was a paper I saw presented at one traffic conference. And the person had a disclaimer, after coming up with this whole model for improved traffic flow. He said, “This model does not account for the heterogeneity of driver behavior.” And that’s a quite polite way to say that, you know, everyone sort of does what they want and we can’t predict that.

RYSSDAL: And so, fundamentally, there’s nothing that’s going to get me home faster.

VANDERBILT: No…. Telecommuting. Telecommuting, personal jet-packs and all the stuff that Popular Science was promising us back in the ’50s.

RYSSDAL: All that good stuff. The book by Tom Vanderbilt is called “Traffic: Why We Drive the Way We Do and What It Says About Us.” Tom, thanks a lot for your time.

VANDERBILT: Thanks, Kai.

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