WHEN Catherine Mulligan, a part-time economist at a non-profit group, commutes from her home in south-west London to her office in Clerkenwell, in the centre, she chooses her departure time carefully. Either she gets on the London Underground early, at around five o’clock in the morning, or she works at home and travels in when the rush hour is over. Such early and late starts may seem an annoyance, but neither is as bad as the alternative. “I avoid the peak hour because it’s hell,” she says.

London’s Underground system is heaving. Since 2007 the number of journeys on the Tube has increased by 30%; passengers now make 4m trips on it each day. The rush hour—which today lasts for nearer three hours—has become even more crowded: since 1991 the number of people crammed on to carriages in the morning and afternoon peaks has increased by nearly 50%. But the congestion is also spreading out. Over the same period the number of people travelling off-peak has almost doubled, with much of the increase in the past decade (see chart). Such shifting patterns hint at the ways in which Londoners are changing the way they live and work.

Much of the overall increase is down to a booming population: some 8.6m people now live in the capital, and more commute in from its outskirts and beyond. Since 2004 the number of people travelling to work in central London has increased by nearly a third. Alongside this, more tourists are coming to the city: between 2004 and 2014 the number of overseas visitors on holiday increased by 52%.

Another reason is that using the Tube has become much easier. In 2003 Transport for London (TfL), the transport authority, introduced the Oyster card, an electronic ticket. This bit of blue plastic “changed the whole equation” of how people get around the city, according to Shashi Verma, TfL’s head of customer experience. Rather than having to buy different tickets for different zones, times and modes of transport, customers can now hop on and off with ease. Since last year “contactless” credit and debit cards have made payment smoother still. All this has persuaded passengers to take more trips.

But the boom in off-peak travel also reflects fast-changing patterns of work. Between 2004 and 2015 the number of people self-employed in London increased by 44%—much faster than the growth in overall employment in the city, which went up by 20%. London has the highest proportion of self-employed people in the country. “Work is a bit more off-the-grid these days,” says Simon, a self-employed artist waiting for the Tube at Old Street station. This means more people travelling to and from work at odd times. In 2003 commuters made up just under half the passengers on the Tube between 7pm and 10pm. By 2013 they accounted for 62%. Their share of traffic in the middle of the day also went up, from 48% to 54%.

Some of those who are self-employed or who work part-time, such as taxi drivers, will not be zipping around the Tube at off-peak hours. But those in other sectors, such as the tech business or service industries, often do. At Second Home, a former carpet-factory in east London which now serves as a trendy workspace for microbusinesses and self-employed people, things are pretty quiet until 10am, says Rohan Silva, its co-founder. But by midday the space is buzzing, he adds—and some people stay there until three in the morning. The Tube is starting to change to accommodate these unusual working hours. Over the past two decades the number of off-peak trains has gradually increased, making it a more reliable service; recent upgrades have improved things further on this front. In January Boris Johnson, the mayor, changed the way that fares are capped each day, moving to a system that has made occasional commuting cheaper for people who work from home a few days a week. From September, five Tube lines will stay open through the night on Fridays and Saturdays; the change is partly motivated by TfL’s discovery that nearly half of those travelling on night buses were on their way to or from work.

Will the off-peak working trend continue? Although many people who work for themselves report high job satisfaction, it is not easy to be self-employed in London, complains Mr Silva. Arranging a mortgage is harder, especially given London’s soaring house prices, and offices often have to be let on strict long-term leases which leave little flexibility for growing businesses. These factors may push people farther out. But for those who still want to work in the capital, avoiding the daily crush will become ever more difficult. Ms Mulligan may find that her five o’clock start becomes a little busier.