Robot cars may not be the solution, but the problem. At least when it comes to the congested streets of inner cities.
Autonomous cars not only promise more traffic safety but also less traffic jams. Whether they can keep the latter is more than uncertain. Some experts fear even greater chaos on the streets.
The idea with the robot cars sounds attractive to city planners. The connected cars drive more closely than people could, never dawdle, automatically and in real time choose the most convenient route and do not have to laboriously search for a parking space at the destination. In the end it boils down to a vision known from more optimistic science fiction scenarios: automated transport capsules transport your passengers efficiently, at lightning speed and without collisions through the cities of the future.
That’s the theory. Apart from the fact that the technology for such a traffic system is not yet ready, the robot car would not come overnight, but slowly and over the years. During this period, autonomous and human-controlled vehicles would share the road space. The robots would have to be considerate of unpredictable maneuvers and, above all, adhere to the traffic rules to the letter. A study by the management consultancy Arthur D. Little observed the effects of this so-called mixed traffic using the example of a real traffic light. Currently - still without any robot vehicles - 3 cars pass the traffic lights on the B43 near Frankfurt per green phase. If only autonomous cars were still on the road, 500 would make it through the intersection before the traffic light turns red again. However, this only works if all cars have a standard length of three meters and the electronically controlled distance between them is a constant one meter - then the queue of cars could drive across the intersection like a freight train in one go.
In mixed traffic, however, when only every second vehicle is automated, the number of possible vehicles drops to 36 - below the current value. There is a very simple reason for this. While human drivers exceed and exceed regulations regarding speeds and safety distances, computers adhere strictly to the rules and would thus stop traffic in coexistence with human drivers. As a result, the analysts see a significantly better flow of traffic only when cities open entire areas only for autonomously controlled vehicles.
In addition to the human-machine difficulties in common road traffic, there may be other problems. Above all, very human: convenience and avarice. A combination of the two weaknesses could lead to congested roads, predicts a study by the Boston Consulting Group. Because the robot car is more convenient and, at least for the individual journey, cheaper than traveling by bus and train, numerous public transport users are likely to switch to the car. The examination expects numerous transfer passengers, especially at distances of less than 6,5 kilometers. As a result, the travel time in the city centers increases by 5,5 percent. Outside of the city, where the traffic is getting thinner, the duration could decrease.
Another mechanism of increasing traffic has discovered researchers from the University of California in Santa Cruz. They fear that autonomous private vehicles will permanently cross in the area after unloading their passengers and wait for the return trip to save the high inner-city parking fees. Already 2.000 autonomous cars in San Francisco would reduce the possible driving speed in downtown San Francisco to less than 2 miles per hour. The study suggests taking countermeasures with special toll systems that make waiting trips more expensive than parking.
Other experts also identify private robot cars as future causes of traffic jams. According to a calculation by ETH Zurich, automation would only have a positive effect on traffic density if private copies were completely banned. Instead, autonomous driving should only be used for robot taxis and in public transport. If ten percent of Zurich's cars were replaced by automated taxis, motorized private transport would drop from 44 to 29 percent. With an increasing number of private vehicles, the effect disappears.
If the analyzes are correct, the cities must come up with regulations for the autonomous future that steer the effects of robot cars in the right direction. This could include regulations on energy consumption and parking rules, as well as restrictions on certain areas of the city. Comprehensive traffic concepts with a mixture of robot taxis, car sharing and intelligent traffic management could also provide relief. And quite a long time before a XNUMX% autonomy quota is reached.