On the basis of the driving profile, the system controls the time windows for driving recommendations, for example for the left-turn assistant. The system uses its own position data and the speed and distance of oncoming traffic to determine how large the gaps are in oncoming traffic for a left-hand turn. Object detection is performed by a long-range radar ready for series production and short-range radars in the vehicle sides, which are already in use in many assistance systems today, such as intelligent Adaptive Cruise Control or blind spot monitoring.
The driver needs assistance when the time window necessary for safe turning is critical or when it becomes difficult for the driver to estimate it. This can be the case at night or in poor visibility, or for inexperienced or elderly drivers. In heavy traffic, the City Assistant System reduces the stress of gap-finding and informs the driver when a suitable gap occurs. Trial runs as part of the research project determined a time window of five to seven seconds in which the system can provide assistance with recommendations. The lower value with smaller gaps in oncoming traffic applies to slightly more dynamic drivers, the upper value for very defensive drivers. The same principle applies to another application: entering a roundabout.
The driving recommendation can be given on different routes. The system can give its advice with optical, acoustic or haptic signals, depending on the driver's preference. In general, the test drivers found an optical display with a large green or red arrow to be the best.