In other words, a few years from now we will have a string of services that we can hardly imagine at the moment brought into our homes over the telephone lines. If the data needed to carry a feature film can be thus compressed, it will not be long before video phones develop from their present tiny screen and jerky image into something akin to broadcast quality. It is quite possible that in 15 years' time ordinary phones will have a screen as a matter of course, and it will be hard to find one without a screen, just as it is hard now to buy a black-and- white television set.
It will, however, no longer be possible to fly supersonic across the Atlantic because no replacement for Concorde will have been built. Technology will have raced forward in one area, but slipped back in another.
In one sense this is just another example of the fact that transport technology is subject to the laws of mechanics, where progress is likely to be incremental, while the advance in electronics is not mechanical and can thus be revolutionary. Concorde used British and French taxpayers' money to push Sixties mechanical technology to the limits, but not enough progress has been made since to make a new generation of supersonic planes financially viable. Nineties electronic technology, meanwhile, is moving so fast that things which were technically possible but used to cost too much - such as video phones - will soon be universal.
The effect is that communications will replace transport. One obvious example is the fax taking over from the letter. If the BT scheme is successful, the ability to receive a film over the phone will replace the journey to the video shop. Companies are increasingly using the video conference instead of the face-to-face meeting. One by-product of the Gulf war was that many companies found that their executives' journeys were not really necessary. Most significantly, some companies are using technology to bring back outworking, a form of production overtaken by the factories of the Industrial Revolution. Instead of travelling to an office, people now work on a screen at home. The computer replaces the commuter.
But, but, but . . . anyone who contemplates this brave new world will appreciate that two powerful forces will limit the extent to which people will communicate rather than travel. One is the human craving for mobility. The fastest-growing market in the world for cars has been Eastern Europe, the result of nearly two generations of artificial restriction on demand. Even Concorde, intended for business travellers, now makes much of its money by attracting the leisure trade: a quick flip down to the Bay of Biscay, a glass of champagne over lunch, go supersonic and back in time for tea.
The other force is the human preference for the clubby atmosphere of the workplace. Ingenious methods are used to supply this social function to outworkers. Some organisations ask their staff to come in to the office every fortnight, so that some face-to-face contact is maintained. BT uses technology. It has pioneered the idea of people working from home on its directory inquiries. During their working shift they have a video link to their supervisor. When they take their break, this link is turned over to them for personal use so that they can have a video natter with each other over their coffee.
So technology is pushing in one direction and human behaviour in another; this tug- of-war will have some fascinating consequences. For a start, fewer people will travel for business, but more will travel for pleasure. That should change the time/cost equation on which the planners base their calculations. It might be worth spending billions building a new fast rail link through Kent if the passengers are business executives hurrying to get to Brussels or Paris 25 minutes faster than they otherwise would. But if most of the people are tourists paying with their own money (who are going to have to queue to get into Euro Disney or Wimbledon anyway), then maybe the extra cost is not justified.
Next, pressure on the commuting infrastructure of large cities will tend to decline, at least in the developed world. People will still want to travel around cities, but the load will be spread. It is illogical to have to develop expensive transport systems that operate at full load for only two 90-minute periods at each end of the working day.
At the moment, the main economic function of city centres is to supply office accommodation - though London now has more office space on its outer fringes than in the West End and the City. Some office work will, of course, continue, but if the city centres become social centres, for culture and entertainment, rather than providers of office space, more people may choose to live in the centre. If they do, then they will need a different transport system: one that does not need so much capacity at the peaks but is more pleasant and safer to use at off- peak times.
It certainly would mean less office space and more housing in city centres. Expect many more office blocks to be turned into high-quality flats over the next 30 years, reversing the pattern of three generations where housing has tended to be turned into offices.
Next, if travel is tending to get more difficult but communications easier, then travelling time will start to be used more imaginatively. This is not just a question of putting video screens on the back of airline seats. It is more a question of feeding Far East market news on to City commuter trains in the morning so that dealers hit the office already knowing what has happened in Tokyo and Hong Kong.
Within offices (which could mean suites of rooms all over the country), the use of communications rather than transport means moving knowledge by electronic signals rather than people or pieces of paper. All boring or routine matters will simply be transmitted by a signal. But because humans respond better to faces than things, any important message will be passed either by a conversation, or a piece of paper. Anything really important will be written by hand, preferably in ink, for that shows that, instead of a cleverly programmed word processor, there must be a real human being at the other end.Reuse content