This contribution presents the results of a microscopic traffic simulation study of the potential effects of an overtaking assistant for two-lane rural roads. The overtaking assistant is developed to support drivers in judging whether or not an overtaking opportunity can be accepted based on the distance to the next oncoming vehicle. Drivers have been found to consider this to be a difficult part of an overtaking manoeuvre. The assistants effects on traffic efficiency, driver comfort and road safety have been investigated using traffic simulation. The results indicate that this type of overtaking assistant can provide safety benefits in terms of increased average time-to-collision to the next oncoming vehicle during overtaking manoeuvres. This safety benefit can be achieved without negative consequences for traffic efficiency and driver comfort. A driver assistance system that supports the distance judging part of overtaking manoeuvres can therefore contribute to improved traffic conditions on the two-lane rural roads of the future.