Every commuter has experienced that sinking feeling of when an unwelcome stranger begins to approach the seat next to them on the bus or train, and while avoiding eye contact is often thought to be the best way of avoiding others, sociologists have discovered other key tactics daily commuters have developed to avoid contact with other travelers.

A group of researchers from Yale University analyzing daily commutes have discovered strategic tactics like the "hate stare" people have developed to make their journey to and from work as bearable as possible.

Researchers said that the "hate stare" was one of the most sophisticated tactics used by commuters keen to deter other from sitting next to them and to prevent others from getting to close, according to findings published in the journal Symbolic Interaction.

However, the most important goal of travelers on public transport is to prevent the "crazy person" from sitting next to them.

Other sophisticated strategies people deployed to keep the seat next to them free included putting a large bag on the empty seat, avoiding eye, pretending to be asleep and leaning against the window and extending the legs, all behaviors that researchers dubbed "nonsocial transient behavior."

"We live in a world of strangers, where life in public spaces feels increasingly anonymous," lead researcher Esther Kim, professor at Yale University, said in a statement. "However, avoiding other people actually requires quite a lot of effort and this is especially true in confined spaces like public transport."

After riding thousands of miles in different coach trips across the United States for three years examining the unspoken rules and behaviors of commuters, researchers found that the deliberate disengagement is actually a calculated social action that requires people to expend a lot of effort.

Kim found that the greatest unspoken rule of bus travel is that if other seats are available, travelers should not pick to sit next to someone else because it "makes you look weird."

However, when all the rows on the bus are filled and more passengers are getting on, seated commuters begin commencing a performance to strategically avoid anyone seating next to them.

"I became what's known as an experienced traveler and I jotted down many of the different methods people use to avoid sitting next to someone else," Kim said.

"We engage in all sorts of behavior to avoid others, pretending to be busy, checking phones, rummaging through bags, looking past people or falling asleep. Sometimes we even don a 'don't bother me face' or what's known as the 'hate stare'," she explained.

Other tactics used by passengers to keep a free seat include leaning against the window and stretching their legs out, looking out the window with a blank stare to look "crazy", sitting on the aisle seat and putting on headphones so people can pretend they can't hear people asking for the window seat and if all else fails lying to others by telling them that the seat has already been taken by someone else.

"This all changes however when it is announced that the bus will be full so all seats should be made available," Kim noted. "The objective changes, from sitting alone to sitting next to a 'normal' person."

Researchers said that race, class, gender and other background characteristics were not main concerns for travelers when they found out that someone had to sit next them, all they wanted was to avoid the "crazy person."

"One rider told me the objective is just 'getting through the ride', and that I should avoid fat people who may sweat more and so may be more likely to smell," Kim explained. "Motivating this nonsocial behavior is the fact that one's own comfort level is the rider's key concern, rather than the backgrounds of fellow passengers."

Researchers found that this type of nonsocial behavior is also motivated by safety concerns, especially for bus travel which is perceived to be more dangerous with badly lit bus stations and the expectation that others will delay or cause inconveniences.

"In a cafe, which is more relaxed, people often ask strangers to watch their stuff for a moment," said Kim. "Yet at bus stations that rarely happens as people assume their fellow passengers will be tired and stressed out."

"Ultimately this nonsocial behavior is due to the many frustrations of sharing a small public space together for a lengthy amount of time," she concluded. "Yet this deliberate disengagement is a calculated social action, which is part of a wider culture of social isolation in public spaces."