ISLAMABAD, Pakistan — For hundreds of thousands of Pakistanis, the miserable, sweaty, cramped commute is coming to an end.

Pakistan, one of the world’s fastest-growing countries, has long lacked an efficient public transportation system. Instead, Pakistan’s 180 million residents have jammed onto unreliable buses and vans prone to breakdowns and grisly traffic accidents.

The haphazard transportation system — which sometimes involves passengers riding on the roofs of buses or sitting on top of each other in taxis or passenger vans — has been the butt of jokes here and abroad. But now, in two of Pakistan’s largest cities, residents are enjoying new mass transit options that even commuters in Western nations might envy.

Rapid-bus systems that together cost $700 million are running in Lahore and the twin cities of Rawalpindi and Islamabad, the capital. In both metropolitan areas, more than five dozen air-conditioned buses circulate in dedicated lanes that use new bridges and tunnels to avoid traffic lights. Commuters wait no more than three minutes for a bus, reducing overcrowding while slashing average commute times by half. And at about 20 cents a ride, the heavily subsidized systems are accessible even to the poor. More