Traditional urban public transit may be on the verge of disruption with the global rise of new mobility services, such as on-demand ride-sharing, car-sharing and MaaS. Tram assets were found to be most vulnerable for disruption as the tram lacks the speed advantage of the metro and de bus has limited dedicated assets. Tram assets could run the risk of depreciation or disutility which can be a problem for the asset owner, tax payers and city residents. Digital On-demand Ride-sharing Services (DORS) are a likely suspect to disrupt the tram, because short term diffusion and substitution with transit is plausible according to literature. DORS providers include ride-sourcing, ride-sharing, ride-splitting, microtransit and combinations of them. All match supply and demand of available vehicles/seats using a digital platform. Scientific literature on potential impact of DORS on tram investments is lacking however. This thesis aimed to contribute to science by exploring the potential impact of DORS developments on investment policy in the tram system in an urban context. A framework for substitution was developed and four distinct scenarios for the impact of DORS on tram substitution and investments were written with the help of an expert panel. Moreover, the implications of these scenarios for tram investment policy were discussed. It was found that the development of DORS can have significant impact on tram investment policy, because substitution to some degree and risk of divestment is probable in three out of four scenarios. Disruptive impact however is probable in only one scenario and impact is larger for the already low demand tram corridors and less to non, for the bigger tram corridors. DORS can be beneficial for tram investments as well. To address this uncertainty in investment policy a robust and multiple strategy approach can be considered. MTA can also gamble by not considering the scenarios or choose one as truth, but this is not without risks.