Researchers at Carnegie Mellon, with other institutions and car manufacturers, have been working on bringing autonomous cars to the roads. In a recent series of tests, their experimental Cadillac SUV drove its passengers from a suburban home to the city’s airport without a single glitch.The lead researcher, electrical engineering professor Raj Rajkumar, said driving through the inner city is another matter. “The traffic around the inner city can be very dense — different kinds of vehicles, bicyclists and pedestrians that particularly jaywalk across the street and so on,” he said. “They are crossing the roads between parked cars, so that is a very complex problem.”