How long do marbles persist in Formula 1 tracks?
It's often said that laptimes in Formula 1 races improve as more and more rubber is laid down to the track. Some tracks already have a large number of races behind them. How does the rubber from previous races get removed from the surface?
The rubber does not stay on the track for years. Tracks that are raced often have better grip in general, because of the continuous addition of rubber. In addition it's worth noting that the asphalt itself wears out when racing is done repeatedly. Rain and winters degrade the rubber.
Street tracks don't have the layer of rubber in place before the weekend. Road going cars driving on the track remove the rubber and don't leave any in the same sense as a racing car with slicks.