A new survey reveals the science behind one of the world's most annoying travel habits.

Passengers putting their feet on train seats is a contentious issue - whether it's after a long day, long evening or we're just relaxed, lots of us do it without thinking twice.

In fact, two in every five people are guilty of putting their feet up during their journey (41%), according to a new survey. Loco2, a comparison and booking platform for train tickets in the UK and Europe, also looked into why people get the urge to put their feet up, and how they can resist.

The study of 500 UK adults highlighted other irritating behaviour commonly found on trains. According to the study, sneezing and coughing without covering the mouth is the most annoying habit (25%), followed by putting feet on seats (19%) and making loud phone calls (19%).

The science of feet on seats

Dr Sara Kayat, GP at GPDQ, the UK's doctor-on-demand app & ITV's This Morning Resident GP, says there's a reason why passengers get the urge to put their feet up on public transport.

"Resting your legs on the opposite seat is undeniably comfortable, but also very disrespectful, unhygienic, and in fact illegal," she says. Few of us might know that there's a by-law that fines passengers £50 for having their feet on the seat and they can receive a police caution.

So why do so many people do it without a second thought?

Kayat claims biology is the answer.

"By elevating our legs, we improve the mobility of fluids in the body - blood flow is increased, which reduces the work your body must do to pump the blood back up to the torso. After a long day at work, or a late night, our bodies need all the help they can get to ease the strain and alleviate any stiffness in our muscles."

What can you do instead?

"My advice to anyone feeling the urge to put their feet on the seats is to listen to what your body is telling you, and move," says Kayat.

"Walk around and help your body pump blood back up to your heart quicker and more efficiently.

"If there's nowhere to walk, passengers can do some simple foot and ankle exercises and stretches such as circling the foot or tapping it up for 10 and down for 10, four or five times which will encourage blood circulation."

Top 5 tips from Loco2 on passenger etiquette...

Think about whether your actions would irritate you or cause you discomfort, if someone else did it.

  1. Always bring a pocket size packet of tissues for your journey - you never know when your nose will start running or if you need to sneeze (this will also reduce the amount of coughs and colds contracted on public transport).
  2. Avoid eating pungent food such as fish, fried food, or fast food. Instead, pack snack bars, biscuits, fruit, and carry a water bottle for your journey.
  3. Take responsibility for your own litter - if you've finished eating a snack, put the wrapper in the nearest bin on the train, or carry it with you until you can dispose of it properly.
  4. Keep personal grooming to a minimum - remember it's a public space. It's okay to do a 'quick fix' of make-up on the train but try to avoid doing anything that can create a mess or leave anything behind, such as cutting nails, plucking eyebrows or applying powder.