Page - (000111) - in Autonomes Fahren - Technische, rechtliche und gesellschaftliche Aspekte

995.6 Simple Implementations of Ethical Rules When encountering an obstacle blocking the lane, the vehicle has three options – it can brake to a stop before it collides with the obstacle or it can maneuver to either side of the obstacle. Figure 5.5 illustrates these three options in the basic scenario. The path in red represents the braking case and the two blue paths illustrate maneuvers that avoid a colli- sion with the obstacle. According to the optimization-based controller, the car will evaluate the lowest cost option among these three choices based on the weights and constraints assigned. In this scenario, going around the obstacle requires crossing into a lane with oncoming traffic or using the shoulder of the road. If both of the lane boundaries are treated as hard constraints or assigned a very high cost to cross, the vehicle will come to a stop in the lane since this action produces the lowest cost (Figure 5.6). This might be the safest option for the single vehicle alone but the car has now come to a stop without the means to continue, failing to satisfy the driver’s goal of mobility. Furthermore, the combination of car and obstacle has now become effectively a larger obstacle for subsequent vehicles on the road. With the traffic laws encoded in a strict deontological manner, other objectives such as mobility are not allowed to override the constraints and the vehicle finds itself in a fully constrained situation, unable to move. If, however, the lane boundaries are encoded as soft constraints, the vehicle now has other options. Possibilities now exist to cross into the lane of oncoming traffic or onto the road shoulder, depending upon which option has the lowest cost. Just as certain segments of the road are designated as passing zones, the cost or strength of the constraint can be varied to enable the use of the adjacent lane or shoulder for maneuvering. If the current segment of road is a passing zone, the cost for crossing into the left lane can be set fairly low. The car can then use the deontological constraint against colliding with other vehicles to only allow maneuvers in the absence of oncoming traffic, such as in the path shown in Figure 5.7. Fig. 5.5 There are three possible options to avoid an obstacle – the car can maneuver to the left or right, as depicted in blue, or come to a stop, as indicated by the red trajectory Fig. 5.6 With hard constraints on road boundaries, the vehicle brakes to a stop in the blocked lane