Thoughts on Traffic

Thoughts about and quotes from the book Traffic by Tom Vanderbilt.

High-level interesting points:

Some interesting not-answered questions:

More detailed notes

Driving creates non-social environments

Humans are inherently social and we've interacted with each other and other animals via social mechanisms (eye contact, movement). Driving puts us in metal containers and speeds us up so we end up not communicating via because they don't work in the driving world we've created.

Being in a car renders us mostly mute.

The flip side of anonymity, as the classic situationist psychological studies of Philip Zimbardo and Stanley Milgram have shown, is that it encourages aggression.

Hamilton-Baillie suggests that there is something crucial in the fact that above 20 miles per hour, humans begin to lose eye contact.

The consequences seem to be disregard for other humans and their safety--esp in regard to risk taking. Without human signals, we often act "inhuman".

The things that work best in the traffic world of the highway—consistency, uniformity, wide lanes, knowing what to expect ahead of time, the reduction of conflicts, the restriction of access, and the removal of obstacles—have little or no place in the social world.

Reduced perception of risk make people act riskier

When something appears safer, people take more risks. Great example of a nonlinear system (chaos theory!). People react to increased perceived safety by being more risky. (Some people think we have "risk homeostasis" however people are so bad at juding risk experts think it's unlikely we can actually maintain a stable level of risk.)

When he wore a helmet, vehicles tended to pass closer than when he did not wear a helmet. Passing drivers may have read the helmet as a sign that there was less risk for the cyclist if they hit him. Or perhaps the helmet dehumanized the rider. Or—and more likely, according to Walker—drivers read the helmet as a symbol of a more capable and predictable cyclist, one less likely to veer into their path. In either case, the helmet changed the behavior of passing drivers. Finally, drivers gave Walker more space when he was dressed as a woman than as a man.

This is one reason why roundabouts are safer -- the y make the risk more transparent. People wouldn't blindly sail into a roundabout like they would an intersection.

This is not in itself a bad thing, because intersections are, after all, dangerous places. The system that makes us more aware of this is actually the safer one.

Crosswalks are another good example. There isn't much research to show that marked crosswalks are safer than jaywalking. Jaywalkers are more alert for oncoming traffic, instead of trusting cars to do the lawful thing.

In India there are lots of distractions on the road, but it seems like this actually can make it safer (for most groups). They call it "conflict" when there's a risk that one movement vehicle could it another.

In conventional traffic-engineering thought, the more conflict, the less safe the system. But again, Delhi challenges preconceptions. In a study of various locations around Delhi, Tiwari and a group of researchers found that the sites that had a low conflict rate tended to have a high fatality rate, and vice versa. In other words, the seeming chaos functioned as a kind of safety device. More conflicts meant lower speeds, which meant fewer chances for fatal crashes. The higher the speeds, the better the car and truck traffic flowed, the worse it was for the bicycles and pedestrians. Even when the roads were crowded, however, they were hardly ideal for cyclists.

Even the cars themselves matter. SUVs are supposed to be safer but people compensate by driving in riskier ways:

Many drivers, particularly in the United States, drive sport-utility vehicles for their perceived safety benefits from increased weight and visibility. There is evidence, however, that SUV drivers trade these advantages for more aggressive driving behavior. The result, studies have argued, is that SUVs are, overall, no safer than medium or large passenger cars, and less safe than minivans.

[Most] people respond to context not rules/signs

The truth is that the road itself tells us far more than signs do. "If you build a road that's wide, has a lot of sight distance, has a large median, large shoulders, and the driver feels safe, they're going to go fast," says Tom Granda, a psychologist employed by the Federal Highway Administration (FHWA). "It doesn't matter what speed limit or sign you have. In fact, the engineers who built that road seduced the driver to go that fast."

Street signs are just artificial rules or guidance. In some cases they tell people what to expect, so they feel more confident they can take it.

Perhaps, but consider the results of a study in Finland that found that adding reflector posts to a curved road resulted in higher speeds and more accidents than when there were no posts. Other studies have found that drivers tend to go faster when a curve is marked with an advisory speed limit than when it is not.
The more stop signs, the more likely drivers are to violate them.

It means that designers/engineers need to design context, rather than hard rules or signage. Children at play signs usually don't slow people down, for instance.

When a situation feels dangerous to you, it's probably more safe than you know; when a situation feels safe, that is precisely when you should feel on guard. Most crashes, after all, happen on dry roads, on clear, sunny days, to sober drivers.

An alternative school of thought started by Hans Monderman pays attention to context as guiding signals that govern behavior. The way the road, barriers (or lack of), signage, and relationship to the surrounding context can all be changed. For example, removing the curb between the sidewalk and road gets drivers to slow down and pedestrians to be more aware. This Vox video has a good description of the context. This all goes back to reinforcing a social world.

Monderman insisted that what he was doing was not anarchy. Instead, he said, he was replacing the traffic world with the social world. "I always say to people: I don't care if you wear a raincoat or a Volkswagen Golf, you're a human being, and I address you as a human being. I want you to behave as a human being. I don't care what kind of vehicle you drive."

The message the road is sending (like how wide it is, curves, signage) matters. Rural areas are more likely to result in deaths (also probably because medical help is farther away).

Rural, noninterstate roads have a death rate more than two and half times higher than all other roads—even after adjusting for the fewer vehicles found on rural roads. Taking a curve on a rural, noninterstate road is more than six times as dangerous as doing so on any other road.

"Affluence breeds traffic", esp from women

Getting into the middle class introduces a lot of good things--and with negative consequences.

Affluence breeds traffic. Or, as Alan Pisarski describes it, congestion is "people with the economic means to act on their social and economic interests getting in the way of other people with the means to act on theirs."

A better economy (more workers), more women in the workforce, and more options for kids extracurriculars makes traffic worse (which women have an outsized role in).

"If you look at trip rates by male versus female, and look at that by size of family," Pisarski says, "the women's trip rates vary tremendously by size of family. Men's trip rates look as if they didn't even know they had a family. The men's trip rates are almost independent of family size. What it obviously says is that the mother's the one doing all the hauling."

Inaccurate perception "amplification"

People seem to think doing easy things will be faster, harder things will take longer, than they actually do.

Research has shown that 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.
Men seemed to underestimate how long it would take to walk, while women seemed to overestimate it—which might explain the differences in parking strategies. Both genders underestimated distances, an effect that grew larger as the distance did.

Nonlinear systems & feedback loops

Creating faster commutes means that people will decide to take that route until it fills up.

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?"

When driving, people choose which route to take based on the known traffic. But they also decide if they should drive or not, where they can live based on their job location, if they have time to visit friends, etc. This is why it's really hard to predict with accuracy what'll happen.

Nash Equilibrium

Individual choices that seem decent for each person create externalities that are amplified. Only coordinate / group action can help.

The drivers are locked into what is called a Nash equilibrium, a strategic concept from the annals of Cold War thinking. Popularized by the Nobel mathematician John Nash, it describes a state in which no one player of an experimental game can make himself better off by his own action alone.

The simple example is rubbernecking, which seems to make sense because it's been "earned" by waiting for it.

The economist Thomas Schelling points out that when each driver slows to look at an accident scene for ten seconds, it does not seem egregious because they have already waited ten minutes. But that ten minutes arose from everyone else's ten seconds.

Congestion taxing is an attempt to motivate systematic action--but it's regressive of course.

Lanes in Delhi

There are lots of vehicle types (48!) compared to just a few in most european areas, which makes lanes less relevant.

In so-called homogenous traffic flows, where every vehicle is roughly the same size and same type, lane discipline makes sense.

The opposite of this is true in Delhi. What this means it that the various vehicle sizes actually allow the roads to be utilized more efficiently.

Laws, corruption and income

Laws work if there's a realistic penalty for breaking the law, or if it's in the best interest of the person who's obeying.

In his book Why People Obey the Law, the legal scholar Tom Tyler posits that people generally comply with laws less because they are deterred by the penalties of not doing so, or because they have calculated it's in their best self-interest, and more because they think it's the right thing to do. Yet they are more likely to think it is the right thing, argues Tyler, if they perceive that the legal authorities are legitimate... Less effective governance means that laws are less effective, which means that people are less likely to follow them.

That means if there's corruption people won't follow the law. But Smeed's Law says that fatalities will rise as more cars come on the road as a country is developing b/c the priority is the economy. Once GDP per capita reaches a certain level people will start caring more about safety then it'll get safer (later).

Let us get the cars and motorcycles on the road first, let us get people commuting to jobs, and then we can worry about safety.

It seems like corruption is more important than income, however.

The lesson is that wealth seems to affect traffic fatalities but corruption may affect them even more. It could just be that lifting GDP lowers corruption and traffic fatalities. But a study by a group of U.S. economists concluded that the statistical relationship between corruption (as measured by the International Country Risk Guide) and traffic fatalities was actually stronger than the link between income and traffic fatalities. What they were saying, essentially, is that money is not enough.

It seems like it's not just lack of bribery as much as it's faith in government.

Loss aversion in traffic

A few factors contribute to "always being stuck in the slow lane" thinking. One is that you don't pay attention to other cars are much when moving vs stopping. But loss aversion is probably the most sound reason.

Frequent lane changes only got drivers to arrive a few percent faster (5%?).

Late merging is better; it utilizes more parallel road

When thinking from a supply chain efficiency POV, this makes a lot of sense because you wait to incur the dependency of being in a single lane.

The most surprising thing about the Late Merge concept is that it showed a 15 percent improvement in traffic flow over the conventional merge.

More cars create more friction

Putting more cars on a road eventually hits a point of diminishing return--where thruput declines vast. Ramp metering (stoplights on onramps) aim to stop freeways from being flooded for this reason. They recommend thinking of cars like rice which is a "granular media": a solid that behaves like a liquid.

Why does the rice jam up as you pour it into the funnel? The inflow of rice exceeds the capacity of the funnel opening. The system gets denser and denser. Particles spend more time touching one another. More rice touches more rice. The rice gets "hung up" from the friction of the funnel walls. Sound familiar? "That's like cars on the highway,"36 says Nagel. "And when you get narrowing of traffic, then that becomes very much stuff trying to flow through the hopper."

Traffic jams are waves of "human friction" that cascade through cars. They can travel up to ~12 mph and once started are independent of cause. Having sufficient space between vehicles prevents this from getting worse.

The closer the vehicles are packed together, the more they affect one another. Everything becomes more unstable. "All of the excess ability for the system to take in any sort of disturbance is gone," says Coifman.