The "car effect" explains why so many people choose to drive even when it's not in their best interest.

People don't always make rational decisions. The entire field of behavioral economics, with all its colorfully named biases and heuristics, is based on our irrationality. If that's not enough to convince you, then let us remind you that Here Comes Honey Boo Boo is a thing.

Go ahead and add cars to the illogical list too. In an upcoming paper in Transport Policy, a group of Italian researchers report that people show an irrational bias toward automobiles — they call it the "car effect." Instead of considering all travel modes and choosing the one that saves the most time and money, people prefer to drive even when it's not the best objective option:

Our key experimental result is that travel mode is significantly affected by heuristics and biases leading to robust deviations from rational behaviour. …

The main bias pointed out by data is the car effect, according to which individuals exhibited a preference for cars over metro and bus in contrast with their economic interest.

The researchers arrived at this conclusion through a series of rather intricate decision games. A group of players started the game with a certain amount of tokens. In the first game, during each of 50 rounds, the players chose whether they wanted to travel by car or by metro. A "travel cost" was determined for each mode — combining price and time — and paid in tokens.

Now here's the catch: while the travel cost of riding metro was fixed, the travel cost of a car varied. Random events, such as weather, accidents, and road work, influenced the cost of car travel. So did "traffic," which was determined based on how many other players also chose car travel during a given round.

In the best scenarios the travel cost of the car was lower, since it's the quicker mode, but if the traffic reached a certain point then riding the metro made more sense. After each round the players received feedback and could make a new choice. Over time they were expected to learn from their mistakes; there was actual compensation at stake, based on performance, so they had a real incentive to do well.

When the car-metro game ended the researchers ran two more experiments with buses replacing the metro option.

In every game the results pointed to a clear "car effect." In the car-metro game, the rate of car use rarely dipped below 55 percent — the point at which the first "traffic" penalty kicked in (below, left). (The "cong. threshold" depicted here represents the congestion penalties that increased the travel cost of a car.) Although the average cost of taking a car ended up being about 50 percent more than taking the metro, people chose cars nearly two-to-one (below, right):

The car-bus games revealed a similar bias toward the car — in contrast to what a rational observer of travel price should have chosen.

The findings are pretty striking when you consider that players received continual feedback after each round. While some players did respond to high car costs by switching modes, the effect didn't last long. "If regret can play a role in travel mode choice, it does not seem relevant in the experiment," the researchers wrote. Once people chose to go by car, they tended to stick with the choice. (Though, to be fair, most players demonstrated some degree of transport "stickiness," no matter the mode.)

The results are even more striking if you consider the players didn't have to actually, you know, ride the subway. In other words, even in a theoretical setting, with no physical interaction necessary, and real monetary compensation at stake, people couldn't set aside their preconceived affection for cars (or, perhaps, their aversion to transit). When it comes to driving, the researchers conclude, logic goes out the window:

This experimental study shows that, in repeated travel mode choice, available information is not properly processed, cognitive efforts are generally low and rational calculation play a limited role.

The games obviously aren't a perfect representation of everyday travel decisions, but they do offer an important lesson for policymakers. For all the technical and spatial hurdles of implementing an efficient urban transit system, there are significant psychological ones too. Sure, some people will make a rational travel choice, and prefer the efficiency and cost of the bus or the metro. But many others will require an incentive to switch that goes above and beyond what the numbers predict they should need.

Top image: gagliardifoto / Shutterstock.com

About the Author

Eric Jaffe
Eric Jaffe

Eric Jaffe is the former New York bureau chief for CityLab. He is the author of A Curious Madness and The King's Best Highway.

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