MACHINES are al- ways talking to me on the train and on the bus. Sometimes, they know what they're talking about, and sometimes, it's nonsense. Sometimes, I talk back.

The Virginia Railway Express onboard talking computer advises me twice a day that a high-speed train may be approaching the station at Quantico. "Rubbish," I sometimes mutter, because I know that the speed limit for trains going through the Quantico station is 55 mph.

The computer also announces the stations, which is helpful in the dark--if the computer gets the information right. But one morning it said: "Now at Fredericksburg. Now at Fredericksburg. " Six times in all the message was repeated, and we were sitting in the Leeland Road station in Stafford.

Then the computer announced that there was a delay ahead, extent unknown, and said we should think about switching to Metro at the next station, which was Brooke, also in Stafford and a long way from the nearest Metro stop.

Metro has a similar announcement system on its buses, and it seems more reliable. I ride the Metrobus a lot, and it makes a lot of stops, but I've heard a wrong stop announced only once.

The Next Bus system, which I wrote about two months ago, is pretty accurate at informing riders when the next Metrobus will actually arrive.

But I trusted it too much. When it told me that the next bus would not arrive for an hour, I supposed that a bus had broken down. More likely, I've discovered, such an announcement means that Next Bus isn't getting a GPS signal from the bus, or else Next Bus is just wrong. I've learned to disregard any predictions that there won't be another bus for an hour, and I just go down to the bus stop, where I'm usually rewarded with a bus at about the time when one is scheduled.