Driverless cars will have challenges in cities

When it comes to adopting self-driving cars and trucks, the easiest part may well be building them. The far more difficult task will be maintaining our urban transportation infrastructures for autonomous vehicles to be functional, safe and practical.

Consider that last year, a modified Audi completed a 3,400-mile cross-country trip, driving itself 99% of the time. The 1% of roadway the car couldn’t navigate on its own: construction zones and other complicated traffic situations–hallmarks of urban traffic.

What will cities have to do to get ready for the transition to the autonomous car? For starters, they will have to maintain everything from complex intersections to lane markings to the specifications expected by vehicle software designers. Without a city’s commitment to certain standards, self-driving autos might freeze in place on streets lacking clear lane markings. Similarly, unmanned vehicles might proceed at speed through an intersection where a stop sign has been removed by college students or knocked down the night before by an impaired human.

Local practices

Traffic rules may be writ in stone, but the autonomous car or truck should also understand local practice. If in a particular city it is customary for trucks to double-park while making deliveries, will the driverless vehicle coming up behind a stopped truck think (in software terms) that it is at a stop light and wait there for the unseen light to change? And in cities where it is customary for human drivers to anticipate the red light turning to green by inching into the intersection prematurely, will the driverless automobile allow for the custom?

Driverless cars can be programmed to be aggressive or patient. But who gets to choose? The software developer? The owner? Or perhaps the local police department?

The duration of a yellow light will be programmed, as it is now, down to a fraction of a second. But upon sensing the yellow when almost into the intersection, will the driverless car stop suddenly or will it speed up? Will the car be programmed to respond differently when it is carrying passengers, comparing in milliseconds the risk of both actions and choosing the one less likely to cause injury?

New responsibilities

Many potential problems can already be handled by vehicles equipped with sensors, controls and warning devices to assist in changing lanes, slowing down or stopping, if vehicles get too close to one another. Cities also can make their traffic signals communicate wirelessly with vehicles.

But naturally that involves spending money that may have to be diverted from fixing potholes and other infrastructural necessities. It also means that increasing and maintaining the wireless-bandwidth capacity used by cars in traffic to communicate will become a responsibility as important as smooth roads and clear signage. The wireless network will have to be pervasive and fast enough to allow for adequate response times to, say, jaywalking pedestrians or erratic cyclists.

These are issues that must be resolved before autonomous vehicles are turned loose on the asphalt. But the ultimate testing will necessarily take place in real cities under real traffic conditions that test tracks can hardly be expected to replicate fully.

Proponents of driverless vehicles focus–sometimes too much–on the benefits the vehicles offer to both individuals and the communities in which those individuals live.

Autonomous cars can drop off people at their workplaces in the heart of a city, then drive to a remote area to park. Later they can drive themselves to pickup points, perhaps designated via a smartphone app, and choose the best route to take into account current traffic. All of these things, in theory, could reduce traffic. But it’s also possible that traffic congestion and the need for parking will increase as a result.

Segway to nowhere

Whether cities will even allow self-driving vehicles will depend mainly on public policy. Despite its popularity as a touring aid in some cities, the Segway–a self-balancing electric scooter–has failed to find acceptance in the broad transportation market in part because there is little uniformity among communities regarding rules governing its use.

Policy debates about autonomous cars are likely to be just as important, starting with such fundamental questions as whether a vehicle should be required to have a driver. A century ago, as motorized vehicles began to share the roads with horse-drawn conveyances, it was understood that a human would be in control of any vehicle on the road.

In the postdigital age, drafters of municipal legislation may be looking at an extended legal battle to redefine what a driver is, and what that driver’s responsibilities and liabilities are. Henry Petroski/Wall Street Journal

Dr. Petroski is a professor of civil engineering and history at Duke University. He is also the author of “The Road Taken: The History and Future of America’s Infrastructure."

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