Assessing the potential dangerous situation in the surrounding environment is a key issue to ensure unmanned tram running safety. However, comparing with driverless vehicle, it is hard to assess the hazard of running safety from the obstacles such as pedestrians and cars around, due to the nonlinear feature of the dynamic model of vehicles and the special running environment. Regarding the problems above, this paper reviews the researches which related to the safety of unmanned tram, and proposes the challenges and potential for active safety of unmanned tram. The technologies and theories suited for tram are discussed. Then a framework of safety assessment for unmanned tram is proposed, which looks forward to improve the works about intelligent and automatic unmanned trams.