Seite - (000106) - in Autonomes Fahren - Technische, rechtliche und gesellschaftliche Aspekte

Implementable Ethics for Autonomous Vehicles94 or weighting so individual goals can be prioritized by making their associated costs much higher than those of other goals. This only works to an extent, however. When certain costs are orders of magnitude greater than other costs, the mathematics of the problem may be- come poorly conditioned and result in rapidly changing inputs or extreme actions. Such challenges are not merely mathematical but are also commonly found in philosophy, for example in the reasoning behind Pascal’s wager1. Furthermore, for certain objectives, the trade-offs implicit in a cost function may obscure the true importance or priority of specific goals. It may make sense to penalize both large steering changes and collisions with pedes- trians but there is a clear hierarchy in these objectives. Instead of simply trying to make a collision a thousand times or a million times more costly than a change of steering angle, it makes more sense to phrase the desired behavior in more absolute terms: the vehicle should avoid collisions regardless of how abrupt the required steering might be. The objec- tive therefore shifts from a consequentialist approach of minimizing cost to a deontological approach of enforcing certain rules. From a mathematical perspective, such objectives can be formulated by placing constraints on the optimization problem. Constraints may take a number of forms, reflecting behaviors imposed by the laws of physics or specific limitations of the system (such as maximum engine horsepower, braking capability or turning radius). They may also represent boundaries to the system operation that the system designers determine should not be crossed. Constraints in an optimal control problem can be used to capture ethical rules associat- ed with a deontological view in a rather straightforward way. For instance, the goal of avoiding collisions with other road users can be expressed in the control law as constraining the vehicle motion to paths that avoid pedestrians, cars, cyclists and other obstacles. The vehicle programmed in this manner would never have a collision if a feasible set of actions or control inputs existed to prevent it; in other words, no other objective such as smooth operation could ever influence or override this imperative. Certain traffic laws can be pro- grammed in a similar way. The vehicle can avoid crossing a lane boundary by simply encoding this boundary as a constraint on the motion. The same mathematics of constraint can therefore place either physical or ethical restrictions on the chosen vehicle motion. As we know from daily driving, in the vast majority of situations, it is possible to simul- taneouly drive smoothly, obey all traffic laws and avoid collisions with any other users of the road. In certain circumstances, however, dilemma situations arise in which it is not possible to simultaneously meet the constraints placed on the problem. From an ethical standpoint, these may be situations where loss of life is inevitable, comparable to the classic trolley car problem [14]. Yet much more benign conflicts are also possible and significantly more common. For instance, should the car be allowed to cross into an adjacent lane and drive against the flow of traffic if this would avoid an accident with another vehicle? In this case, the vehicle cannot simultaneously satisfy all of the constraints but must still make a decision as to the best course of action. 1 Blaise Pascal’s argument that belief in God’s existence is rational since the penalties for failing to believe and being incorrect are so great [13].