Roman: This is 99% Invisible. I’m Roman Mars.
Roman: I want you to conjure an image in your mind of the White Stripes.
Roman: Not those White Stripes. But the white stripes that divide the lanes of traffic going in the same direction on a major highway. How long are those stripes? You can spread your arms out to estimate if you want to. Over the course of many years, a psychology researcher named Dennis Schafer at Ohio State asked students from many different parts of the country this question.
Dennis: The most common response was two feet.
Roman: So, if you’re like most people you estimated that those white stripes are two feet long. Maybe a little more. But if you did, you’d be very, very wrong. This is Tom Vanderbilt.
Tom: My name is Tom Vanderbilt. I’m a writer in New York and the author of, Traffic: Why We Drive the Way We Do and What It Says About Us.
Roman: Every three pages of Tom’s terrific book, Traffic, I can probably turn into a 99% Invisible episode, but back to the highway.
Tom: Well, early on in my research, I was talking to a highway engineer.
Roman: And he said if your car is ever broken down on the side of the road…
Tom: If you’ve ever been forced to get out of your vehicle on a highway…
Roman: Just take a moment to notice what a strange landscape it is.
Tom: To have me standing near a road sign. These road signs are huge. I mean they’re not meant to be experienced as humans on foot. They’re meant to be experienced at 75 miles an hour.
Roman: With that clear view typeface.
Tom: Perfectly visible, retroreflective.
Roman: And then, there are the white stripes.
Tom: If you actually you kind of got out of your car and were able to walk on a closed highway and walk from one end of those stripes to the other, you’d find that… I mean, years ago in the United States, the highway standard was 15 feet long which is longer than a car itself.
Roman: Current federal highway administration guidelines suggest a length of 10 feet with 30 feet between the dashes.
Tom: That’s something that is shocking to people.
Roman: And remember, most people in the Schafer study said that those stripes were two feet long.
Tom: That’s such a vast gulf between…it’s not sort of like, they’re actually five feet. We thought they were two, margin of error kind of thing.
Roman: And it goes back to this fundamental point that when you’re in a car at high speeds, you’re experiencing only a sense of the landscape rather than the actual landscape.
Tom: This kind of sense of landscape has been presented to you, to essentially make you feel comfortable.
Roman: And to make a highway work at what are really evolutionarily ridiculous speeds for a human to travel.
Tom: You have this big flat wide open kind of stretch of road that even if you have a 65 mile an hour sign, the message of the road is telling you something entirely different. I think that’s really where a lot of our behavior comes from. Sometimes you have sort of willful speeding, willful kind of lawbreaking. But a lot of it is just people are paying attention to the visual messaging on the road, not to their speedometer.
Roman: Long dividing lines and clear vistas give the illusion that you’re going at a reasonable speed. As soon as something encroaches into view, you get a sense of how fast you’re going. That’s one reason why those temporary concrete walls that crews put up right next to the road during construction are so unnerving. The air and perception of a white stripe length is attributed to the fact that when we drive on the highway, we tend to look so far ahead that we usually only experience the dashes and gaps when they are very far away, at an angle where they look shorter. But there’s no consensus as to why people all over the country were so consistently wrong with the two feet estimate.
Tom: It’s, yeah, become my favorite…one of my favorite cocktail party facts.
Roman: Mine, too.
Tom: Stump the driver with this white stripes information.
Roman: I don’t want to leave with the impression that the wide dividing lines are uniform, though.
Tom: You won’t find a 10-foot highway lines on a, say, a Boulevard in New York City.
Roman: And you probably won’t find 10 or 15 foot stripes on bridges or highway on-ramps.
Tom: Or let’s hope you don’t because that’s kind of an entirely inappropriate design language for that space.
Roman: Limited access highways are designed for a very precise purpose.
Tom: The highway is meant for uninterrupted fast flowing traffic, get people from point A to Point B as quickly as possible with no interruptions. I mean, that sort of environment does not work in cities or suburbs.
Roman: The problem is when that approach is grafted into places where it doesn’t belong.
Tom: People are actually kind of paying the price for this right now in some suburban environments where you find this kind of arterial highways that were built almost to a highway engineering standard with, again, this long sight lines, wide roads encouraging people to go fast. And then we went and built all kinds of development along those arterial highways which was never really supposed to be there.
Roman: But with so many people driving on these roads, they became absolutely irresistible to commerce.
Tom: This is kind of the new American Main Street, right? Where you have your Costco’s and your fast food and all sorts of in and out parking lots, driveways, drive thru’s. Yet, people also going very fast and a guy named Eric Dumbaugh does a lot of research suggesting that these are really some of the most dangerous places to currently drive in America. Not crowded urban cities, which is what a lot of people would think.
Roman: The whole approach is called the forgiving road.
Tom: The idea was that to first try to minimize the potential that a crash could happen through, again, through lack of obstacles, generous sight lines, all these sorts of things. But then if crash did happen to kind of mitigate the effects of what would happen to not punish the driver for the mistake that he will inevitably make, this was– I’m quoting some of the language from the time. So, you see that nowadays in things like in California, you’ll have your guardrails that are sort of wire guardrails that if a car strikes that guardrail, it tends to catch on the guardrail rather than being bounced back out into traffic which causes another series of collisions.
Roman: So, this forgiving road is a positive thing in terms of good safety engineering.
Tom: But they were so sort of seduced by it that the call was made to bring it into that even the surface street network. So, things like street trees began to be deemed hazards by engineers. Just outright hazards. I mean, and that makes sense on a high speed country road. But if you’re talking about a residential street where you’re not supposed to be going more than 25 anyway, is the presence of a street tree on the side of the road where it’s providing shade and comfort to pedestrians. Is that the same sort of hazard? Is it even a hazard at all?
Roman: The conclusion many planners came to was, Yes, trees are a hazard.
Tom: You find pre-war suburbs. You have a street, a set of trees and then the sidewalk. Post-war, this sort of shift began to happen where the trees removed on the other side of the sidewalk.
Roman: Suddenly pedestrians were put into the position of being the buffer between drivers and those menacing trees.
Tom: There was sort of a pernicious thing that happened here is that, as you move those trees away, the visual sensation of the road became wider. And if there’s one kind of iron law of traffic engineering that gets into this visual perception thing as well, the wider a road is or is perceived to be….
Roman: The faster driver speed tends to increase.
Tom: And, of course, the final…if you look at sort of 1990’s era, suburbia, that they just kind of eliminated the sidewalk and the trees altogether. So, that was sort of the final solution. Just eliminate any kind of hazard.
Roman: And Tom Vanderbilt says you can almost date a subdivision’s development based on that shift.
Tom: This points to one of the problems about road engineering is that humans tend to consume the extra engineering measures that have been built in for their safety. Much in the same way, I like to draw the analogy with some of the research that’s been done on food packaging by Brian Wansink at Cornell University. You’re doing experiments where if you give people, just random group of people large buckets of popcorn filled to the top with popcorn and give them a smaller amount of popcorn in a smaller package that they’ll just eat more of the larger package whether there– it has nothing to do with their level of hunger, it’s just the size of the package influences their behavior. And I think a lot of our road environments are sort of like that. They’re over-engineered for the safety and then we tend to consume a lot of the extras getting us back to this kind of homeostatic edge that we’re always kind of playing with, I think.
Roman: 99% Invisible is Sam Greenspan and me, Roman Mars. It’s a project of 91.7 local public radio, KALW in San Francisco and the American Institute of Architects in San Francisco.