Summer in Japan: When the temperature soars in Tokyo, some 31 million people get hot and bothered - but not bothered enough to take their holidays. David McNeill reports

Tokyoites: your heart goes out to them, as my mother used to say. They have a lot to put up with at the best of times. In July and August, however, things really get tough.

The summer here begins for real when the rainy season wrings itself out in late June. A blanket of thick, oppressive heat drops on the city and makes itself at home for two months.

Venturing outside becomes a sweaty test of endurance, running or cycling an invitation to sunstroke. Yet throughout Tokyo every morning that's what you'll see: hordes of people, many in black suits, walking, cycling and running to the hub of life in most large Japanese cities - the train station.

By the time they get to the chilly refuge of a crowded air-conditioned train where most will have to stand for well over an hour, cheap suits are damp, collars are too tight and shirts stick to backs. And it's still only 7.30 a.m.

More than 31 million people now fight for space in the Tokyo region and 20 million of them have to get to work or school every day. Forced out of the city to the dreary suburbs by extortionate rents, the commute for most gets longer by the year - about two hours a day on the train.

Herded into carriages filled to more than 200 per cent capacity, squeezed through some of the world's largest stations and popped out ready for another day's grind in grim corporate bunkers, the stoic determination with which Tokyoites greet this daily ordeal and keep the Asian financial hub humming is surely one of the sociological wonders of the modern world.

The equivalent to the population of Dublin files through one sweltering, teeming station - Shinjuku - in a single day.

The only time I have seen a train more than a minute late was after a commuter jumped on to the tracks, one of about 10,000 people to commit suicide this way last year.

All the tools of modernity are used to help shunt this mass of humanity around the city - a vast, computer-controlled transport network and enough air-conditioning to power a small African country. Yet a little humanity gets lost in the process as people move like tiny cogs in a vast industrial machine.

The obvious solution is to send everyone off on holidays in August and shut down the city for the worst of the summer. Surely the wheels of government policymaking are turning in this direction? Not likely. According to the government's figures, salaried workers in Japan are given just 18 days a year off, only half of which are actually taken, not all at one time.

A typical Japanese holiday lasts three or four days. Vacations abroad are the preserve of the young, the old or the rich, and the vast layer of people in the middle who support the economy have to make do with a day trip to Katase beach or a hot-spring resort.

To many Irish Times readers the idea that you can be entitled to holidays and not take them might seem bizarre. To understand it you have to enter the world of the Japanese company where the pressure to prove yourself and not let others down is very strong.

"I didn't want to cause trouble to others by taking a week off," is a typical way of explaining why nine days a year paid holidays are left to wither on the company books.

This hole in people's lives that a fortnight with the kids in Hawaii or Canada might have filled surely contributes no end to the natsubate, or summer fatigue, that everyone complains of in July and August, and it also helps explain the odd popularity of pep drinks.

The market for these small jolts of caffeine, vitamins and amino acids is worth a remarkable $1.7 billion a year in Japan. Generations of TV viewers have watched commercials showing tired salarymen dosing up on a tonic in front of harried wives, before flying out the door ready for their trek to the office.

Last week on my train ride home from central Tokyo, there was a fight between a couple of drunken salarymen. Jackets off, collars loosened and shirts damp with sweat, the men could be heard arguing all the way about a new manager.

"He's incompetent," said one. "He's worth 10 of you," said the other. And so on.

By the time we got to Minami Osawa, about 70 minutes from the city, they seemed to have made up. But as the doors opened for the bigger man's stop, he turned and said "Baka!" [idiot\] over his shoulder.

The little guy pulled him back into the carriage. Fists, glasses and briefcases flew before the train doors shut on the half-in, half-out men.

The conductor came running and gave them a stern lecture about causing "trouble" to others. The men apologised and bowed and the big guy sloped off home. The train pulled into the terminal of Hashimoto about one minute late.

The surprising thing is that it doesn't happen more often.