The common traffic misperception I submitted for the CityLab staff post on stubborn myths we’d like to retire was just one of many encountered, yet again, during 2015. Here’s a full list for your reading-while-not-driving pleasure. Safe travels this New Year’s, and all those to come.
1. More roads mean less traffic
Via the staff myth post:
The most enduring popular traffic myth holds that building more roads always leads to less congestion. This belief is a perfectly logical one: if there are 100 cars packed into one highway lane, then building a second should mean there’s 50 cars in each. The problem, as transportation researchers have found again and again, is that when this new lane gets added the number of cars doesn’t stay the same. On the contrary, people who stopped driving out of frustration with traffic now attack the road with an enthusiasm unknown to mankind.
While residents of heavily congested metro areas have a suite of four-letter words to describe this effect, experts call it “induced demand.” What this means, simply put, is that building more road eventually (if not always immediately) leads to more traffic, not less. Fortunately, local leaders are starting to distinguish reality from myth when it comes to induced demand. Unfortunately, the best way to address it—congestion pricing—remains all-but politically impossible in the U.S. That pretty much leaves one thing to do: deal with it.
2. More transit means less traffic
Public officials love to promise that a new public transport system will relieve congested roads. But over the long term (again, if not the short), this belief is just as misguided as the idea that more roads mean less traffic. Some residents will indeed leave their cars at home and take the bus or metro; others will see this new space on the road and fill it. A 2015 analysis of the new Expo light rail line in Los Angeles, for instance, found no change in travel times along nearby Interstate 10.
Of course, reliable transit is still an integral part of the ultimate traffic solution: congestion fees. And strong bus or rail systems offer other benefits to cities, from better overall better to more economic might, regardless of whether or not rush-hour remains a nightmare.
3. Bike lanes make traffic worse
Bike lanes are all too often the punching bags of the transport planning world, and in 2015 they once again took all sorts of shots from local residents, retailers, and religious groups alike. One mainstay anti-bike argument holds that converting general road space into a bike lane is bad for traffic.
But to respond in rhyme: when good design’s in place, that’s just not the case. New York City proved as much with bike lanes recently installed on Columbus and Eighth avenues. By reducing the width of car lanes from 12 to 10 feet and adding protected left turns, the city was able to preserve vehicle volume and actually reduce travel times by 35 and 14 percent, respectively.
4. A wider road is a safer road
Speaking of 12-foot lanes versus 10-foot lanes, the common perception holds that the wider option is a safer design, since it gives drivers a bit more room to maneuver. But what some new research published in 2015 showed quite clearly was that wider lanes also invite cars to drive faster—erasing whatever safety benefits might be gained by additional space, and actually leading to more dangerous streets.
An evaluation of intersections in Toronto and Tokyo found lower crash rates in lanes that were closer to 10 feet, compared with those that were wider than 12 feet. “Given the empirical evidence that favours ‘narrower is safer’, the ‘wider is safer’ approach based on intuition should be discarded once and for all,” wrote the researcher who conducted the study. Oh, and the 10-foot lanes still moved plenty of traffic.
5. The next lane over is moving faster
On average, drivers change lanes every 1.25 miles. But the routine nature of these moves belies the basic risk involved in making complex decisions about speed and distance involving multiple enormous moving objects. And while it might seem like the next lane over on the highway is always moving faster, the truth is that’s usually not the case.
Instead, researchers have shown that what you’re seeing is a visual illusion created by the fact that it takes longer to be passed than to pass someone else. In other words, you spend more time being overtaken by three cars in the next lane than you do zipping past three other cars. That gives drivers the general impression that they’re losing ground even when both lanes have similar average speeds.
6. Everyone else’s bad driving is the reason for traffic
The super fun game Error-Prone that came out in 2015 reflects the basic principles behind “shockwave” traffic jams. What this means is that every imperceptibly imprecise move in a car—tapping the brake a bit too hard, or holding the gas a bit too long—sends a ripple effect of congestion back through the rest of the road. As Traffic author Tom Vanderbilt has said: "You're not driving into a traffic jam. A traffic jam is basically driving into you."
So it’s not all those other terrible drivers holding things up. It’s everyone’s inability to hold a steady speed and following distance—a failure that test trials on closed courses has confirmed. Autonomous vehicles won’t experience much of this problem, but human drivers suffer through it every day.
7. You need to get lots of cars off the road to reduce traffic
The much-feared Popemageddon traffic jams that were supposed to snarl New York, Philadelphia, and Washington, D.C. didn’t happen during Francis’s 2015 U.S. tour. One reason was that public officials, with the help of social media, alerted people about the potential problem. But the bigger explanation is that removing just a few cars from a road has a disproportionate impact on congestion.
Experts would call this traffic being “non-linear.” What they mean is that the relationship between cars and delay is not one-to-one. If you remove just 1 percent of commuters off the rush-hour road in especially high-traffic corridors, as some work has shown, you can reduce travel times by 18 percent. So when a few drivers stay home during, say, a Pope’s visit, a lot of others benefit.
8. Removing an urban highway would be a traffic nightmare
This summer Toronto became the latest city to consider tearing down an urban expressway that cut through the center of town. Though city planners wanted to remove the highway, others (including the mayor) worried that removing it would result in a crippling amount of traffic. That mindset eventually won the day (though the fight isn’t over).
It’s true that not every urban interstate can be torn down without having a major short-term impact on traffic. But drivers adapt extremely quickly to changes to the road network—a phenomenon that experts refer to as “disappearing traffic.” Some people shift their routes, travel times, or modes when an existing road closes; others simply decide not to make a trip at all. As the authors of one study put it, “predictions of traffic problems are often unnecessarily alarmist.”
9. There’s no downside to cheap gas
It was hardly a painful year for Americans at the pump. Gas prices started 2015 incredibly low and they ended it even lower, with average fuel costs in the U.S. dipping below $2 this month. That’s great for middle-class bank accounts, but it’s bad for all the hidden social costs of driving, which have been estimated at some $3.3 trillion (with a “T”) a year. Of that total, at least $1 trillion represents time lost to congestion both at home and at work.
10. Drivers pay the full cost of road maintenance
The point of the gas tax is to cover the cost of keeping American roads in a state of good repair. In its early days, back in the 1960s, this road user fee did handle the vast majority of maintenance expenses (though not all of them). But since that time its powers have steadily eroded, with Americans now paying some of the lowest gas taxes in the world.
The federal highway bill passed in late 2015 made the situation even worse. Instead of raising the gas tax for the first time in more than 20 years, officials raided yet more money from other funding pots, further destroying the relationship between driving fees and road repair costs. The result is a significant infrastructure maintenance crisis with little end in sight.