I am standing on the edge of Piazza Venezia – Venice Square – smack in the heart of old Rome, and am trying to imagine this seething ocean of cars, trucks, scooters, buses, bicycles, pedestrians and terrified tourists on Segways stuffed instead with diverless vehicles, and I can't.

Piazza Venezia is one of the busiest squares in Europe. It is dominated by the Vittoriano, the enormous white monument built by Victor Emanuel, the first king of unified Italy, and Palazzo Venezia, a former papal palace that centuries later housed Mussolini's office. Five busy roads pour endless rivers of traffic into the square 24 hours a day. Incredibly, there are no stop signs. It possesses a single traffic light, designed to control the traffic on one of the roads leading out of the square, not into it.

Essentially, the square is a free-for-all, yet it works; the traffic keeps moving. While Italian drivers are notoriously aggressive and have a healthy disrespect for stop signs, red lights and speed limits, they also adhere to driver's etiquette. A quick glance from one driver to another can be interpreted as, "Not on your life," or, "Go ahead, but quickly." I spent half an hour watching the traffic one morning this week and did not hear a single horn go off in frustration or anger.

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Driverless cars are the next big thing on the tech front. Google has been testing its robot car fleet for years and, next year, Britain will allow such cars on public roads for the first time. Almost every car maker is working on them. Their sales potential might be way overblown.

Take Piazza Venezia. The traffic moves even though it's bumper to bumper. The scientists got it wrong; the shortest distance measured was not between one molecule and another; it was the distance between the front bumper of one Italian car and the back bumper of another.

Now imagine Piazza Venezia populated only by driverless cars, with their multitude of sensors plotting the speed, trajectory and distances of all moving objects in the vicinity with, allegedly, all the real-time accuracy and sophistication of a NASA rocket in flight. I would imagine total gridlock. If a robot car senses another car 5 centimetres ahead of its bumper, wouldn't it slam on the brakes? Wouldn't driverless cars be a godsend to pedestrians, scooters and bicycles? If you knew cars would automatically stop if a pedestrian came close to the front end, you could walk across Piazza Venezia blindfolded and survive as the traffic screeched to a halt around you.

I also wonder whether the wheeled robots would be programmed to break the law for the sake of commuting expediency. Every driver everywhere does it sometimes. In some countries, such as Italy, it's not only tolerated, it's a respected manifestation of the creative process. Sometimes a driver has to exceed the speed limit, drive partly or entirely on a sidewalk, go the wrong way on a one-way street or make a right turn from the far left lane (I do all the above on my Vespa, sometimes in plain view of the police). If every driver in Rome obeyed the traffic rules, nothing would move.

I also wonder whether freeing a driver to do non-driving activities would appeal to Italians. Since Italian drivers are already adept at shifting gears, smoking, calling their mothers, gesticulating with both hands and leering at women – all simultaneously – handing over the steering and braking functions to a computer might seem superfluous.

On a more serious note, I wonder whether the big touted benefit of robot cars – saving lives by removing the human error factor – might be a bit of overselling by the developers of such cars. Writing in BBC News Magazine earlier this year, Adam Gopnick noted that driving sometimes involves ethical decisions that have to be made in a split second. Suppose a raccoon and your pet dog race across the street at the same time (admittedly, a pretty rare occurrence) and to save one, you would have to hit the other. You, as the driver, would hit the raccoon. The computer piloting your car would not be able to distinguish the two animals.

Or how about this situation? You're driving at speed at night and spot a small deer in the middle of the highway. You may decide in a nanosecond that it's safer to hit the deer than swerve and risk ending in the ditch, wheels up. Would the computer processors of a driverless car make the same move?

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Don't get me wrong. I do think driverless cars will find a market. They would be a godsend for people who are bad drivers or, because of old age or failing eyesight, cannot drive. The idea of programming one to pick up my teenage daughter from a party at midnight, so she can avoid relying on some drunken lout for a ride home, appeals to me a lot. But I also think that in most markets, driverless cars won't take off nearly as fast as the tech-loving futurists say they will. Just because the technology is possible doesn't mean it's desirable. And we have not even talked about what evil fun an expert hacker could have breaking into the networks running the robot cars. Think national gridlock, or worse, within a second.