Traffic (22 page)

What you may not realize, when you find yourself driving on a crowded city street, is that many of your fellow drivers on that crowded street are simply cruising for parking. The problem is not so much the lack of street parking but the plentiful abundance of free or underpriced parking. This finding has sparked the fiery crusade of Donald Shoup, a bearded, bow-tied, and bicycling economist at the University of California, Los Angeles, and the author of a seven-hundred-page, cult-sensation tome titled
The High Cost of Free Parking.

The mantra used by Shoup, and his growing legion of supporters (dubbed “Shoupistas”), is the “85 percent solution.” In other words, cities should set prices on parking meters at a level high enough so that an area’s spots are only 85 percent occupied at any time. The ideal price, says Shoup, is the “lowest price that will avoid shortages.” Spaces with no meters at all, in a city like New York, are total anathema to Shoup. “People who want to store their car shouldn’t store it on the most valuable land on the planet, for free,” he told me in his office at UCLA, where a vintage parking meter sits atop his desk. “Something that is free is very misallocated.” This is why people who want to see free Shakespeare in the Park performances in New York City have to begin waiting in line as early as the day before (or hire people to do it for them), why cafés that offer free Internet access soon find themselves having to limit the time patrons can spend at a table, and why it can be so hard to find a parking spot.

The reason people cruise is simple: They’re hunting for a bargain. In most cities, there is a glaring gap between the cost of a metered parking spot and that of an off-street parking garage. Looking at twenty large U.S. cities, Shoup has found that, on average, garages cost
five times
more per hour than metered street spots. The reason garages can charge so much, of course, is that the streets charge so little. When free parking spaces are available, the discrepancy is even higher, particularly for a free spot that can be held for many hours. And so people are faced with a strong incentive to drive around looking for parking, rather than heading into the first available garage.

On the individual level, this makes sense. The problem, as is so often the case in traffic, is that the collective result of everyone’s smart behavior begins to seem, on a larger scale, stupid. The amount of extra traffic congestion this collective parking search creates is shocking. When Shoup and his researchers tracked cars looking for parking near UCLA (they rode bikes, so other cars would not think
they
were looking for parking and throw off the results), they found that on an average day cars in one fifteen-block section drove some 3,600 miles—more than the width of the entire country—searching for a spot.

When engineers have tried to figure out how many cars in traffic are looking for parking, the results have ranged from 8 percent to 74 percent. Average cruising times clock in at anywhere from three minutes to thirteen minutes. What’s so bad about three minutes? you might ask. As Shoup points out, small amounts can have big consequences. In a city where it takes three minutes to find street parking, and where each space turns over ten times per day, each of those spaces will generate thirty minutes of cruising per day. At 10 miles per hour, that means the average space generates five miles’ worth of driving per day, which works out to a yearly sum that would get you halfway across the United States—not to mention a heap of pollution.

But it is not simply that cars are driving while looking for parking. They’re driving in specific ways. There is the inevitable slowing to check out a prospective spot, the stopping to study whether a spot is valid, the actual jockeying into the spot, or what Shoup calls “parking foreplay,” in which the person detects that a space is about to be vacated and stops to wait. This may seem a minor offense, but as I discussed earlier, one car stopped on a two-lane street creates a bottleneck that cuts traffic capacity
in half.

This is worsened further by the inevitable delays and gaps caused by drivers battling to merge before they reach the stalled car. One person’s small act is felt by many. The famed urbanist William H. Whyte once espied this phenomenon during a traffic study of Manhattan. In his “mind’s eye,” he observed, one particular street was always “jammed” with double-parked cars (a result of underpriced parking, in Shoup’s view). But when he actually counted the number of double-parkers, he was shocked to only find “one or two” at any time. “It seemed odd that so few could do so much,” he wrote. “But the number, we found, was not the critical factor. It was the amount of time a lane was out of action because of double parking. Just one vehicle per block was enough.”

The more time one spends looking for parking, of course, the greater chance one has to get in a crash, which then creates even more congestion. Interestingly, parking itself, according to some studies, is responsible for almost one-fifth of all urban traffic collisions. While some engineers think curb parking should be done away with entirely for safety and traffic-flow reasons, others counter that the rows of parked cars actually make things safer for pedestrians, both as a physical barrier and a source of “friction,” like street trees, that can drop traffic speeds by an estimated 8 miles per hour.

To return to the Wal-Mart study mentioned earlier, the massively capacious big-box lots might seem to have little to do with crowded city streets. But there is plenty of cruising in large, free lots. It is simply that the incentive to save money has been entirely replaced by the incentive to save distance (and, theoretically, time, even if that ends up not being the case). In fact, there is
always
parking at Wal-Marts, so much so that the company lets people in recreational vehicles treat it like a campground. As Shoup points out, at places like Wal-Mart, the planners who dictate what size the parking lot should design for “peak demand”—that is, Christmas Eve—thus guaranteeing that most of the year, the lot has an abundance of empty spaces. The estimated demand comes from the parking-generation models of traffic engineers, which are filled, Shoup notes, with strange irregularities, like the paradoxical fact that banks with drive-up windows are required to have more parking spaces than banks without drive-up windows.

Shoup argues that there is a circular logic at work in parking-generation models, one similar to that found in other kinds of traffic models. The demand for parking is treated as a foregone conclusion: Planners measure the number of people parked at a typical free parking lot in a location without much public transportation. The new Wal-Mart is built and, lo and behold, it attracts lots of cars. As Shoup writes, “The parking demand at new land uses with free parking then confirms the prediction that all the required spaces are ‘needed.’” Planners seem to ignore the fact that they are helping to dictate demand by providing supply. There are lots of cars in lots because parking is free.

As Shoup reminds us, though, Wal-Mart’s free parking, like the free curb parking in cities, is not really free; the term is an oxymoron. We pay for “free” parking all sorts of other ways—and not just as a surcharge on the goods we buy. Parking lots are not only the handmaidens of traffic congestion, they’re temperature-boosting heat islands, as well as festering urban and suburban floodplains whose rapid storm-water runoff dumps motor oil and carcinogenic toxins like polycyclic aromatic hydrocarbons (from shiny black sealcoat) into the surrounding environment and overwhelmed sewer systems. They represent a depletion of energy and a shockingly inefficient use of land—in a study of one Indiana county, Bryan Pijanowski, a geographer at Purdue University, found that parking spaces outnumbered drivers by
three to one.
The whole parking equation is like a large-scale version of that person at the mall, circling to get a “better” spot to save time and energy, and not realizing how much time and energy they have wasted looking for a better spot.

Traffic patterns are the desire lines of our everyday lives. They show us who we are and where we are going. Examined more closely, this movement, like all desires, is not always rational or efficient. Traffic is a great river of opportunity, but often, as with the poor choices made with parking policy, we’re just spinning our wheels. In the next chapter, we’ll look at some more ways to get unstuck.

Why More Roads Lead to More Traffic (and What to Do About It)

When a road is once built, it is a strange thing how it collects traffic.

—Robert Louis Stevenson

In the summer of 2002, a labor dispute at the ports of Los Angeles and Long Beach halted the flow of goods for ten days. Ships backed up, containers of Nikes and Toyotas lay dormant, and five-axle trucks, the kind that carry the containers from the ships to their destination, suddenly had nothing to haul. The impact on I-710, the route most trucks take from the ports, was immediate: In the first seven days of the shutdown, there were nine thousand fewer trucks on the highway.

Frank Quon, deputy district director of operations for Caltrans, the state highway authority, noticed something peculiar happening that week. The
total
traffic flow dropped by only five thousand vehicles. “Nine thousand trucks disappeared off the system,” Quon told me in his office in downtown Los Angeles. So why did the total flow drop by barely over half that? “Cars filled in the volume. Another four thousand cars just jumped in the mix.”

Almost instantly, drivers just seemed to know that the 710, where speeds jumped an average 67 percent during the shutdown, was a good place to be. They may have heard it on the traffic report, or a friend may have told them. Or they took it one day, learned that it was uncongested, and decided to take it the next day as well. What is curious is that the 710 was not necessarily sucking drivers off more crowded routes. “If you look at the parallel routes, like the 110 freeway,” Quon said, “the volumes remained essentially the same.”

It was as if drivers had suddenly materialized out of nowhere to take advantage of a highway that was, by Southern California standards, almost too good to be true. And it was: By the following week, when the ports reopened, the traffic was even worse than before the shutdown as trucks scrambled to catch up on deliveries—truck traffic, as you might have guessed, jumped much more than the total traffic. Now those new cars were deciding to stay away from the 710.

Engineers like Quon call what happened on the 710 a case of “latent demand.” “It’s the demand that’s there but because the system is so confined that demand doesn’t materialize,” Quon explained. “But when you create capacity, that latent demand comes back and fills it in.” Basically, people who would have never taken the 710 because it was too crowded suddenly got on. We don’t really know what they did before. Perhaps they used local streets. Perhaps they took public transportation. Perhaps they simply stayed home.

The point is that people are incredibly sensitive to changes in traffic conditions (sometimes
too
sensitive, as we shall soon see) and they seem capable of quickly adapting to even the most drastic changes in a road network. Engineers have a phrase: “It’ll be all right by Friday.” This rough rule of thumb means that even if on Monday something major happens that throws off the usual traffic patterns—a road is closed, a temporary detour set up—by the next Friday (or so) enough people should have reacted to the change in some way to bring the system back to something resembling normal. “When a change in a traffic pattern occurs, there’s a state of flux for a period of time,” Quon said. “We usually have everybody plan on expecting a two-week period. Things are going to keep balancing. Some days will be good, some days will be not so good, and then at the end of the two weeks, there will be an equilibrium in the system based on those changes.”

The latent demand that the newly fast 710 highway in Los Angeles had unlocked is often described by another phrase, “induced travel,” which is really just a twist on the same thing: There was a new incentive to drive on the highway. Imagine that instead of trucks disappearing from the 710, two new lanes were added. The result would be the same. Congestion would drop, but the highway would become more attractive to more people, and, when it was all said and done, traffic levels might be even higher than before. This is the “more roads create more traffic” argument you have no doubt heard before. It is actually an argument older than automobile traffic itself. In 1900, William Barclay Parsons, chief of New York City’s subway system, wrote, “For New York there is no such thing as a solution to the rapid transit problem. By the time the railway is completed, areas that are now given over to rocks and goats will be covered with houses and there will be created for each new line a special traffic of its own. The instant that this line is finished there will arise a demand for other lines.”

Over a century later, people are still arguing. There is a huge and enervating literature about this, which I heartily do not recommend. Do we build more roads because there are more people and more traffic, or does building those roads create a “special traffic all its own”? Actually, both of these things are true. What’s in dispute are political and social arguments: Where and how should we live and work, how should we all get around, who should pay for it (and how much), what effect does this have on our environment?

But studies suggest that induced travel is real: When more lane-miles of roads are built, more miles are driven,
even more so
than might be expected by “natural” increases in demand, like population growth. In other words, the new lanes may immediately bring relief to those who wanted to use the highway before, but they will also encourage those same people to use the highway more—they may make those “rational locators” move farther out, for example—and they will bring new drivers onto the highway, because they suddenly find it a better deal. Walter Kulash, an engineer at Glatting Jackson, argues that road building, compared to other government services, suffers disproportionately from this feedback loop. “You build more roads and you generate more use of the roads. If you add mightily to the sewer capacity, do people go to the bathroom more?”

If you do not believe that new roads bring new drivers, consider what happens when roads are taken away. Surely all the traffic must simply divert to other roads, no? In the short term, perhaps, but over time the total level of traffic actually
drops.
In a study of what they called “disappearing traffic,” a team of British researchers looked at a broad list of projects in England and elsewhere where roads had been taken away either for construction or by design. Predictably, traffic flows dropped at the affected area. Most of the time, though, the increase in traffic on alternative routes was nowhere near the traffic “lost” on the affected roads.

In the 1960s, as Jane Jacobs described in her classic book
The Death and Life of Great American Cities,
a small group of New Yorkers, including Jacobs herself, began a campaign to close the street cutting through Washington Square Park, in Greenwich Village. Parks were not great places for cars, they suggested. They also suggested
not
widening the nearby streets to accommodate the newly rerouted flow. The traffic people predicted mayhem. What happened was the reverse: Cars, having lost the best route through the park, decided to stop treating the neighborhood as a shortcut. Total car traffic dropped—and both the park and the neighborhood are doing just fine.

We have already seen how engineers’ models are unable to fully anticipate how humans will act on “safer” roads, and it is no different for congestion. It makes sense, mathematically, that if a city takes out a road in its traffic network, traffic on other streets will have to rise to make up for the lost capacity. If you removed one pipe in a plumbing system, the other pipes would have to pick up the slack. But people are a lot more complex than water, and the models fail to capture this complexity. The traffic may rise, as engineers predict, but that in itself may discourage drivers from entering a more difficult traffic stream.

Or it may not. Los Angeles currently operates with a freeway system largely built in the 1950s and 1960s. Its engineers never imagined the levels of traffic the city now sees. As John Fisher, head of the city’s DOT, put it, “They say, ‘If you build it, they will come.’ Because we didn’t build it doesn’t mean the people stopped coming. Freeways weren’t built, but the traffic is still coming anyway. There’s more and more traffic. The bottom line is that the L.A. area is going to be a magnet whether we build freeways or not. People are still going to want to come here.”

This raises the question of how much more successful a city Los Angeles could be if it had built all the freeways it never did, if one could magically whisk from downtown to Santa Monica in a few minutes. Then again, how desirable would a place like Beverly Hills be if the freeway that had been planned for it, to “cure” L.A. traffic, was now running through it? Wouldn’t the increased speed just attract even
more
people? Is traffic failing Los Angeles, or is it a symptom of a thriving Los Angeles? Brian Taylor, the planner at UCLA, argues that people often focus single-mindedly on congestion itself as an evil, which, leaving aside for a moment the vast, negative environmental impacts, misses the point: What great city has not been crowded? “If your firm needs access to post-production film editors or satellite-guidance engineers,” Taylor notes, “you will reach them more quickly via the crowded freeways of L.A. than via less crowded roads elsewhere.” Density, economists have argued, boosts productivity. Traffic engineers like to use the example of an empty restaurant versus a crowded restaurant: Wouldn’t you rather eat at the crowded one, even if it means waiting in line?

Users of
Match.com
, a dating service, are said, in places like Washington, D.C., to specify that they would like to meet someone who lives no more than ten miles away, presumably to avoid the hassles of congestion. Some have seen this as a social problem: Traffic is literally
killing
romance! Cupid is thwarted by congestion! This, too, misses the point: People move to places like Washington, D.C., in fact, because there are so many other people nearby. This is why cities play host to speed-dating events. There is so much “romantic congestion” packed into one room that daters must speed through all the potential choices. In Idaho, you will not face traffic trouble in driving well beyond the ten-mile range to meet dates; actually, you will probably have little choice. In any case, as anyone who has been in a long-distance relationship knows, those intervening miles can be a good way of deciding if a potential mate is really worth it.

What about all that time wasted in traffic? Surely that is costing us—$108 billion in the United States in 2000, according to one estimate. But a number of economists, most notably Anthony Downs of the Brookings Institution, have pointed out the potential flaws in these estimates. The first is that people seem willing to accept much of the delay, instead of paying to eliminate it (which means the “real” loss is closer to $12 billion). Another problem is that some models measure the costs of congestion against a hypothetical ideal of a major city in which all commuters could move at free-flowing speeds during rush hours—a situation that has not been possible since Juvenal’s Rome. Still another complication is that models judge the money people lose in traffic by a hypothetical wage rate, but this assumes that people would get paid for any time saved in traffic—or that they would somehow use the time saved in traveling to do something productive, not simply travel
more.
(As mentioned in the last chapter, many people seem to enjoy the time spent in their car.) Finally, no one really knows how much money we
make
because of our transportation system, so the losses due to congestion may be marginal. A useful comparison is the Internet. It imposes all kinds of costs on our productivity—YouTube videos, spam, fantasy football—but does anyone not think these are an acceptable cost for all the good we derive from it?

There is another way, a bit more subtle and complicated, that new roads can cause more traffic: the Braess paradox. This sounds like a good Robert Ludlum novel, but it actually comes from a classic 1968 paper by a German mathematician, Dietrich Braess. Put simply, the paradox he discovered says that adding a new road to a transportation network, rather than making things better, may actually slow things down for all its users (even if, unlike in the “latent demand” example,
no
new drivers have been induced onto the roads). Braess was actually tapping into the wisdom of a long line of people who had in some way thought about this problem, from the famous early-twentieth-century British economist Arthur Cecil Pigou to operations researchers in the 1950s like J. G. Wardrop.

You would need an advanced math degree to fully understand Braess and his ilk, but you can grasp the basic problem they were all getting at by thinking in simple traffic terms. First, imagine there are two roads running from one city to another. There is Sure Thing Street, a two-lane local street that always takes an hour. Then there is Take a Chance Highway, where the trip
can
be half an hour if it’s not crowded, but otherwise also takes an hour. Since most people feel lucky, they get on Take a Chance Highway—and end up spending an hour. From the point of view of the individual driver, this behavior makes sense. After all, if the driver gets off the highway and goes to Sure Thing Street, he or she will not save time. The driver will save time only if others get off the highway—but why should they?