In the past, catching public transport in San Francisco meant standing on a street corner for 20 minutes wondering when the next bus would arrive, or if, indeed, it would arrive at all. Things began to change in 1999 when the city started experimenting with the NextBus automated tracking system. Until recently, the system was only of limited use as it worked only on a few routes. But now that it's expanding citywide, NextBus is taking much of the stress out of riding Muni. Here's how it works. Passengers can log on to NextBus' Web site, call Muni's information line, or check the LED displays at some bus stops to find out in real time when the next vehicle will be approaching a particular location. Although NextBus doesn't make the bus come faster or more frequently, there's something empowering about knowing that you have time to go grab a cup of coffee before the next No. 22 arrives.