Train doors are particularly difficult for some people.
In my country, it is known as the ‘grind to a halt’ syndrome.
I’m sure it has been around for a long time, but now it has been exacerbated by the ‘reading of cell phone messages while walking’ phenomenon.
Who said blokes cannot do two things at once. This guy is smiling and checking his phone while walking! Which is technically three things, but who’s counting?
Despite what is said, people generally cannot do two things at once, and the brain knows this, so it decides that reading trumps walking and, so as not to frighten the person carrying the brain, it slowly shuts down the ability to walk. Rather an elegant solution, assuming you are not the person walking behind them at the time.
A recent variant is the ‘suddenly speed up again’ effect. It sometimes kicks in as you go to go around them.
This is a tricky one which requires more study.