Why can it be dangerous to overtake on an unobscured, straight road?

The selected combination is correct because all three points highlight the dangers associated with overtaking on a straight road.

1. Estimating the distance of an oncoming vehicle as being too great can lead to a miscalculation of how much time you have to safely complete the overtaking maneuver. This can result in being caught in the oncoming vehicle's path.

2. Estimating the speed of the oncoming vehicle as being too low is equally dangerous; it may encourage a driver to initiate the overtaking process when, in reality, the oncoming vehicle is approaching much faster than perceived.

3. Estimating your overtaking distance to be shorter than it is can result in incorrect judgments about the space required to safely pass the vehicle in front and return to your lane before meeting the oncoming traffic.

These estimates are crucial as they directly relate to the safety considerations outlined in German traffic laws, which emphasize the importance of assessing speed and distance accurately before making potentially hazardous maneuvers like overtaking. Understanding these factors can help prevent accidents and ensure safer driving practices.