TOKYO -- You're at a pay phone in the heart of downtown, midway through a crucial conversation with, say, your boss, your lover or your best customer. Things are going great until some impatient jerk starts banging on the phone booth, pointing at his watch and demanding to know how much longer your call will take.

To this occasional social dilemma, the Japanese have invented a solution.

Phone booths in downtown Tokyo's Ginza district are equipped with a pair of buttons to let those using the booth communicate with folks waiting outside. One button lights a green sign on the door of the booth that says, "I'm almost done." The other lights a red sign reading, "I'll be talking a while longer."

For the Japanese, those little buttons fill an important social purpose by preventing a face-to-face confrontation, a dreaded occurrence that much of Japanese etiquette and the deliberately vague Japanese language are designed to avoid. For foreigners here, though, the phone booth buttons are among a series of small but ingenious ideas that make life a little simpler.

Daily life in this bustling, crowded country isn't always a bed of roses, and there are some obvious ideas -- for example, street names and house numbers -- that have not yet caught on. But there are also surprising innovations that have not been tried in the United States but should be.

The telephone card: This is a simple invention that eliminates the problem of using a pay phone when you have no change, and the annoyance of putting quarters into a phone that won't give back change.

Anywhere in Japan -- as in some European countries -- you can buy a small card with a magnetic strip that can be used in place of cash at almost any pay phone in the country. You buy the cards in advance in $8, $16 or $40 denominations. When you need to use a pay phone, you put this prepaid card in a slot, and the cost of your call is subtracted from the total value of your card. No coins needed, and with the card you are charged only for the time you actually use.

Battling colds: Since Japan has one of the world's highest population densities, people almost always find themselves in crowds -- at work, on the street, on the train. In such a setting, contagious illness becomes more of a problem, a characteristic phenomenon of winter here is a pesky problem called the "Tokyo cold" -- a common cold that just will not go away.

Thus, many government buildings here have two kinds of water fountains. One dispenses plain drinking water; the other has a mixture of water and mouthwash, for people with a cough or sore throat.

To keep from contaminating others, people who catch cold here routinely don surgical masks and wear them everywhere until the ailment is cured. Thus, when a train pulls into a subway station and its doors open, it is common to see a horde of masked people pouring out onto the platform like massed doctors exiting an operating room.

Highway safety: Just as in the United States, Japanese driver education classes routinely teach potential drivers always to maintain a safe distance behind the car ahead. The recommended gap here is 40 meters (130 feet) at a speed of 24 mph.

But how do you know if you are 40 meters back? On Japanese highways, that question is answered every mile or so by a series of small roadside signs marking distances of 30, 60 and 100 meters. The whole purpose is to help drivers keep a safe distance from your rear bumper. A few of them actually do so.

Trading papers: This one is a good idea for newspaper readers, although publishers might not stand up and lead the cheers.

Japanese newspapers have just about enough reading material to last a half-hour subway ride. So what to do with the newspaper once you've finished it? At some train and subway stations, there are plastic boxes on the platform where people can drop off the paper they've finished reading -- and pick up a different one someone has left. The only rule is that you should leave a paper whenever you pick one up.

The refund booth: Japanese trains are famous for running on time, and almost always do. Even so, the announcers in the stations who report that a train is due to arrive almost always say, "Sorry to have kept you waiting . . . " -- even if the train is on time.

Since being on time is so important, the trains here routinely give customers a refund if the train runs late for any reason. Every station has a window called the seisanjo, or "fare adjustment booth," where customers can collect some money back if their train is slower than the schedule says it should be.

The seisanjo gave rise to one of the great Japanese evening TV news stories. It seems a jeweler was riding the bullet train from Tokyo, site of his shop, to his home in the suburbs. He got up from his seat to go to the rest room, leaving two small bags on the seat -- one filled with precious jewels, the other with that day's earnings from the shop.

When the jeweler returned to his seat, he found that both money and jewels had been stolen. Since there was no way to search everyone on the crowded train, he thought that his goods and money were lost forever.

But this turned out to be a thrifty thief. He slipped off the train with the money and the jewelry at the next stop. Noticing the train was a couple of minutes late, the robber went to the fare adjustment window to get back the 50 cents he was owed.

He got his refund, all right -- but in his haste, he left behind the bags of money and jewels, worth tens of thousands of dollars, which were eventually reunited with their rightful owner.