We all know the trouble with city buses.

Schedules are a cruel joke. You can stand at a bus stop for 35 minutes in the rain and nothing happens. So you duck into a bodega for 20 seconds to buy an umbrella and -- of course -- you come back just in time to see your bus zoom by.

Traffic tie-ups. A rider who needs complex directions. Pothole repairs. They all conspire to make your commute a harrowing roll of the dice.

So it was welcome news when the MTA said Monday that it will expand Bus Time -- its GPS tracking service -- to routes in Brooklyn and Queens by March 9, making good on its promise to offer the program citywide. This will allow the city's million-plus daily bus riders to track the location of the next bus in real time at bustime.mta.info or by text message (511123).

If the next bus is a long way off, some riders may want to hike to the nearest subway stop. Others may want to grab a cup of coffee. Whatever. The idea is to make commuting less painful by giving riders more control over their lives.

But what about bus riders with no access to the Web or to text messaging?

The answer is bus-stop countdown clocks that display next-bus information on electronic signboards.

A pilot project is in progress on Staten Island.

The Riders Alliance, a transit watchdog group, held a rally in Manhattan last weekend in hopes of persuading the city to install the clocks citywide. We hope Mayor Bill de Blasio and the City Council got the message.

At $20,000 a pop, the countdown clocks aren't cheap. But the city doesn't need to put them at every bus stop -- just at the major ones in each borough.

There was a time when the MTA was accused of giving its lumbering bus system short shrift. But no more. By equipping 5,500 buses with GPS at a cost of $7,200 each, it's building a better system for beleaguered riders.

Now the city needs to green-light some help.