In recent weeks, there have been bus strikes and gas shortages. Every day, without fail, an old Fiat breaks down, bringing traffic in some stretch of Cairo to a halt. During one recent bus strike, the subway trains were full of people trying to escape the chaos above, slipping into an orderly parallel world available for just one Egyptian pound (about 16 cents).

Outside the stations, vendors packed the plazas, selling strawberries, SIM cards and socks. Many stations were plastered with posters of a presidential candidate, Hazem Salah Abu Ismail, whose bearded, smiling face was famously ubiquitous before his recent disqualification from the race because his mother is a United States citizen. Several platforms provided refuge for couples, the kind of privacy a city of 18 million people can lack.

Some of the trains were old, dating back to the opening of the subway, in 1987, with wooden window shades on the outside that recalled Cairo’s old Beaux-Arts buildings. Some people said that when the trains were empty, they felt nostalgic for the old trams.

During rush hour, there is no nostalgia, just the crush dreaded by commuters around the world.

Three million people ride the subways each day, according to Ahmed Abdel Hady, the subway authority’s media coordinator. Construction on Cairo’s third line, now under way, will bring trains from the working-class neighborhood of Imbaba all the way to the airport, providing an alterative to the clogged surface roads and bridges.

“If the subway stopped, all of Egypt would stop,” Mr. Hady said, bragging about a service that actually covers only a small patch of the country. “It’s the fastest, cheapest and safest means of transportation in the country.”

Mr. Hady said the line was largely unaffected by the frequent labor strikes following the revolution. But labor activists said even the vaunted subway was not immune: workers have been holding regular sit-ins for the last week, complaining that the new head of the Metro has failed to honor previous pledges for wage increases and bonuses.