LONDON, Sept. 3 - London's subway network virtually shut down at the height of the rush hour on Monday evening when 2,300 maintenance workers walked off the job in what they said would be a three-day strike over pensions and security.

Transportation officials then closed nine subway lines, the bulk of the system. They said it was too dangerous to keep the network going without the workers, who are responsible for maintaining and repairing tracks, signals, trains and the like. Just three lines - the Jubilee, Northern and Piccadilly lines, which are maintained by workers who belong to another union - were operating Monday night.

Commuters across London left work early in a rush to make it home before 6 p.m., when the strike began. Commuters arriving later found that their stations were locked or - in those stations still operating - that signs had been put up explaining that most of the lines had stopped operating.

Transport for London, the local agency that runs the subway system, predicted that the strike would cause "massive disruptions for millions of Londoners" and urged passengers to seek "alternative routes" - a difficult proposition in a city as large, sprawling and choked with road traffic as London.

The maintenance workers say that if their demands are not met, they will remain off work for three days, and strike again for another three-day stretch next week.

Adding to the general feeling of annoyance, the mayor, Ken Livingstone, said motorists driving into central London during business hours would still have to pay the congestion charge of 8 pounds a day, or more than $16, during the strike.

DRIVING a taxi in New York City can be a grueling, thankless job. It is also a unionless job. But on Wednesday, many of the city’s 44,000 licensed cabdrivers are planning to go on strike for 48 hours to protest the new global positioning systems being installed in the city’s 13,000 yellow cabs.

While the Taxi and Limousine Commission supports these devices and has mandated that they be up and running in the city’s entire fleet by January, many cabdrivers — myself included — see this new technology as one big expensive headache. Perhaps the commission should listen to cabdrivers before pushing a device that we’d be better off without.

The device has no navigational abilities. The monitor, which is set into the partition separating the driver from the passenger, cannot be seen or accessed from the front of the cab. It does not give directions or plot routes. All it does is keep track of where you are — both on- and off-duty — and this information is then stored in the commission’s databases.

Officials at the commission say the primary purpose of the devices is to track lost property and make sure cabbies aren’t taking passengers from point A to point B by way of point Z. Sadly, there are some bad cabdrivers out there who take visitors for a “ride,” but in reality, we have much more to fear from our passengers than they have to fear from us.

However, for me and many of my fellow drivers, privacy issues aside, it’s all about money. With prices ranging from around $3,250 to $4,000 to lease and install each unit, the initial costs alone are enough to drive some cabbies out of business. For private owner/operators, this could kill their year.

The costs continue to pile up after the devices are installed. The test drivers who already have the touch-screens have reported finding the monitors covered in spray paint, stickers, soda and scratches.

Mayor Michael R. Bloomberg said yesterday that the city would not back down in its determination to install credit card and video devices in city taxicabs despite a threatened two-day strike by a major cabdrivers' group.

"All they would be doing is hurting themselves," the mayor said of a planned 48-hour work stoppage by the New York Taxi Workers Alliance, scheduled to begin at 5 a.m. tomorrow. "Hopefully, they won't want to sit there and let all the other taxi drivers have extra fares while they earn nothing."

Nevertheless, the mayor said he hoped that "cooler heads will prevail and that nobody will strike."

The alliance claims to represent more than 7,000 hack-license holders among more than 20,000 active cabbies. Bhairavi Desai, the group's executive director, said that 50 volunteers were out leafleting and talking to drivers yesterday at taxi stands, terminals and hotels.

In competing Manhattan press conferences yesterday afternoon, rival advocacy groups said that (1) there could be a citywide taxi strike in September, and (2) there would not be a strike.

“We are ready to have a 48-hour strike on Sept. 5 and Sept. 6,” said Bhairavi Desai, the executive director of the New York Taxi Workers Alliance, as she stood near a line of taxis outside Pennsylvania Station. “We are ready, willing and able to walk out.”

The Taxi Workers Alliance said in a press release that it wants to work out a resolution with the Taxi and Limousine Commission to avert a strike.

Two hours later, Fernando Mateo, a spokesman for the New York State Federation of Taxi Drivers, said no walkout was ahead.

Standing in front of the Taxi and Limousine Commission office on Rector Street in Lower Manhattan, he said: “Read my lips: There will be no strike.”

The two groups, which have been vying for the right to speak for city cabdrivers, were at odds over a decision by the Taxi and Limousine Commission that requires all of the city’s 13,087 medallion taxis to be equipped by the end of January with new technology including a global positioning system, a credit card system and a monitor that provides passengers with an electronic map. About 1,300 taxis have already had the devices installed.

The G.P.S. that will go in cabs will not be used to navigate routes, but will be connected to meters and track the vehicle’s movements. Commission officials have called it an “electronic trip sheet” and said it could be used to help recover lost property.