DTM already opted to move their pre-season testing from Monza to the Hockenheimring as a safety precaution due to the coronavirus outbreak, and the sport's organisers have now decided to carry out the testing behind closed doors as well to prevent potential infections.
No visitors
Testing days usually attract some fans, although not nearly as many as a typical race would, as is the case with Formula 1 and pre-season testing in Barcelona.
While visitors don't come in great numbers, DTM are not taking any chances with spreading the coronavirus, conducting the testing behind closed doors. Only the drivers, their respective teams and media members will be allowed in.
The organisers look to guarantee the health and safety of everyone, including the visitors, and the only way for them to guarantee that is to keep testing behind closed doors.