London was braced for widespread disruptions to its public transit system on Tuesday, as train drivers prepared a labor strike that is expected to affect vital parts of the British capital’s underground rail network.

Transport for London, the city transportation authority, expects service on the London Underground, known as the Tube, to halt completely on at least two lines and to be reduced elsewhere this week. Trains that do run will be less frequent and very busy, and commuters should expect delays, the authority warned.

Train drivers are striking as part of a long-running dispute over their shift patterns, working conditions and terms of employment. Rising prices are squeezing living standards for many people in Britain, and other sectors have been hit by labor unrest, with many hospital doctors recently taking part in strikes.

Disruption to Tube services could have a significant economic impact. With more than three million journeys made each day on the network, stores, restaurants and businesses face potential financial losses if workers who can work from home avoid the capital.

“Nobody wants to see strike action or disruption for Londoners,” the office of London’s mayor, Sadiq Khan, said in a statement. “Strikes have a serious impact on London’s businesses and commuters.” The mayor’s office urged both sides to “get around the table to resolve this matter and call off this planned strike action.”

How much of London’s travel network is closing and when?

Transport for London expects the strike action to begin at noon on Tuesday, with normal service until midmorning. The strike is scheduled to end at noon on Friday, although disruption are likely to continue into the early evening.

During the strike, no trains are expected to run at all on the Piccadilly and Circle lines. Service will also be stopped on sections of two other lines: the Metropolitan line between Baker Street and Aldgate and the Central line between White City and Liverpool Street.

Other transportation services and London’s trams are expected to function normally as are a vast majority of the city’s buses.

Why are train drivers striking?

The National Union of Rail, Maritime and Transport Workers, which represents many drivers, wants a 32-hour week over five days. The transportation authority proposes reducing the working week for drivers from 36 hours to 35 hours over four days.

The union, also known as the R.M.T., says the authority’s proposal amounts to five days’ work compressed into four, prompting concern that drivers will be working longer, more tiring shifts, and that the resulting fatigue could affect safety.

The union also argues that the health and the life expectancy of London’s Tube drivers are affected by shift patterns, exposure to dust particles and the psychological effect of suicides in the underground system.

Eddie Dempsey, the union’s general secretary, accused Transport for London of seeming “unwilling to make any concessions in a bid to avert strike action,” adding that the approach would “infuriate our members who want to see a negotiated settlement to this avoidable dispute.”

There are around 3,300 train drivers on the London Tube, and their annual salary is £71,160, or about $96,000, according to information provided by the authority in January.

What does London’s transportation authority say?

Transport for London argues that it is offering train drivers an additional day off while bringing the London Underground system in line with the working patterns of other British train companies, improving reliability and flexibility at no additional cost.

“The changes would be voluntary,” and those who wish to continue a five-day working week pattern would be able to do so, said Claire Mann, Transport for London’s chief operating officer. She added, “We urge the R.M.T. to call off this action, which will disrupt Londoners, and continue to engage with us.”