Due to climate change, more sustainable passenger and freight transport is in need. Rail is considered a more sustainable mode of transport compared to others such as road transport. Usage of rail lines that are currently under-utilised could help increase the sustainability of transport through enhanced utilisation of them. This study looks at the Marston Vale Line, identifying it as under-utilised, and through the use of event-based simulation modelling, observes the current utilisation level and develops ways in which the spare capacity can be utilised, with more passenger services, as well as local rail freight, which is identified as a potential use of spare capacity on the Marston Vale Line. Possible local freight that can be transported by rail is investigated and combined with current and possible additional passenger services in varying levels, in five different scenarios, which are evaluated to propose the best workable option for the Marston Vale Line, with journey time and reliability also considered. Particular theoretical attention is proposed to create a more environmentally friendly mode for the transportation of passengers and freight, and not just shifting more from road to rail using the idea that rail transport is more sustainable than road transport.