Travelers on long bus rides prefer sitting next to an empty seat. What's surprising is how strongly they prefer it, and why they want it.

Esther Kim, a sociologist from Yale University, spent over three years taking long bus rides throughout the United States. Connecticut to New Mexico, California to Illinois, Colorado to New York, she crisscrossed the country. But on the way, Kim unearthed a wealth of information on the behavior of bus travelers.

There's a marked change when it's announced that the bus will be full and there won't be any empty seats. Now people can no longer keep their expanded personal bubble. And their goal shifts to hoping that they get to sit next to a normal person...

What stood out most was how unsocial passengers were, what Kim calls nonsocial transient behavior. The mindset seems to be that buses are for riding, not for personal interaction.

The first thing Kim found out was the great unspoken rule of bus travel: you don't sit next to someone else if other empty seats are available. Even though buses are public places, passengers consider the empty seat next to them part of their personal space. In an effort to avoid contact with others, they set up an invisible bubble around them, which includes the empty seat.

The most common way of doing so involves placing items on the seat, anything from a coat to luggage. The bigger the barricade, the better. Other favored tactics include leaning against the window and stretching out, essentially using your body as a barricade, sitting in the aisle seat and turning up the iPod so you can't hear people asking if the seat is taken, avoiding eye contact with passing passengers, and looking out the window with a blank stare and projecting craziness.

When all else fails, the ultimate weapon is to lie and say the seat is taken.

There's a marked change when it's announced that the bus will be full and there won't be any empty seats. Now people can no longer keep their expanded personal bubble. And their goal shifts to hoping that they get to sit next to a normal person: avoiding the crazy person at all costs. The race, social class and gender of the seatmate isn't important, as long as they're not crazy.

Some of this unsocial behavior is driven by fear and discomfort. Interstate bus travel was once a common, inexpensive way to see the country. Now it's regarded as dangerous and is seen as the travel option of last resort. Even the bus stations themselves are unattractive and sometimes intimidating places. In cafes, public places with a more relaxed atmosphere, people will often ask others to watch their belongings for a moment. Kim found this rarely happened in bus stations.

Bus travelers appear to view the entire trip as an ordeal that leaves them physically and psychologically exhausted. They just want to make it through the trip.

All this decidedly nonsocial behavior on buses may be a very reasonable adaptation to difficult circumstances. At times, Kim found herself caught up in the culture, becoming an expert private space maker and exhibiting other nonsocial behaviors that are uncommon to her. So Kim understands why bus travelers may have a very good reason to leave the sociability at home. But Kim sees this as part of a larger problem where people increasingly act less socially in all public places--the pursuit of loneliness, if you will. Nonsocial transient behavior is supposedly temporary. But Kim worries that these behaviors may end up trickling into people's everyday lives.

What type of experiences have you had on long bus rides? Are you eager to meet new people and talk to strangers or are you afraid of the crazy person? Have you ever met anyone interesting, maybe even your soul mate? Or are long bus trips something best forgotten?

An article on Kim's bus study appears in the journal, Symbolic Interaction.