LONDON — BRITAIN, which invented the railways in the 19th century, has decided that its 20th century love affair with the car must be cooled. In a decisive policy break, Transport Secretary Malcolm Rifkind has declared that the best way to avert massive traffic snarls in coming years is to begin to switch passengers and freight back from road to rail.
And he is promising a green light to private operators prepared to challenge state-owned British Rail's monopoly of the country's train system.
Mr. Rifkind's policy switch has two other important implications. According to Richard Hope, former editor of the Railways Gazette, it means that Britain's antiquated rail network can at last expect to get a new lease of life to coincide with the opening in 1995 of the Channel Tunnel train link between Britain and France.
Politically, Labour Party opposition spokesmen note that Rifkind's approach represents the abandonment of one of Margaret Thatcher's most stubborn prejudices.
John Prescott, Labour's ``shadow'' transportation secretary, says the former prime minister's personal aversion to railways had been ``the main reason'' why the Conservatives, in 12 years in office, had failed to accept that a transportation policy based on cars and trucks would ``ultimately strangle Britain.''
During her long premiership, Mrs. Thatcher hardly ever traveled by train.
Addressing a transportation conference in London, Rifkind, who was named to his post last November by John Major, the new prime minister, said: ``I must declare myself, enthusiastically and unequivocally, as desiring to see far more traffic, both passenger and freight, traveling by the railways.''
Rifkind faces some daunting figures in attempting to come up with a transportation policy for the post-Thatcher era. Official forecasts show that, under the old policies, road traffic in Britain would be likely to grow by up to 112 percent by 2025. Rifkind wants to reverse the trend that has resulted in only 7 percent of freight currently being carried by rail, compared with 50 percent in the 1950s. In continental Europe, the railways carry about two-fifths of freight, and the proportion is growing.
Rifkind sees private enterprise as the best means of revitalizing the ailing system.
A special act of parliament, permitting private operators to bid to operate on stretches of British Rail track, is likely to be introduced later this year.
Britain would need a massive switch of transportation emphasis if it is to emulate the largely rail-based policies of its neighbors in continental Europe. Unlike the French, who have a 20-year plan to update 2,000 miles of track and to develop the existing network of high-speed trains, the British are barely at the planning stage.
Martin Mogridge, a transportation expert at University College, London, says commuters in southeast England ``endure cattle-truck conditions.'' He notes the Post Office has canceled its contract with British Rail and has moved to road and air transportation to get mail to its destinations on time.
Mr. Mogridge says also that if private operators are to get a fair deal in their efforts to break British Rail's monopoly, the government must appoint a track authority with powers to allocate stretches of track.
Another obstacle likely to be thrown across the government's path is the trade unions.
Jimmy Knapp, leader of the main rail union, said Rifkind's proposals raised ``many operational and safety problems, which will be difficult, if not impossible, to overcome.''
The rail union jealously guards the system whereby train drivers must serve a long apprenticeship before being allowed on long-distance routes.
Mogridge describes this as ``a legacy from the steam age.'' Private companies operating rail systems would demand the right to train their drivers in months rather than years, he said.
Rifkind's officials concede that Britain's road transportation lobby can be expected to battle hard to keep its share of the freight market.