This study estimates the value of travel time savings (VTTS) for commuters who travel to Colombo city in traffic congestion when the proposed monorail system is in place. The model considers a mono-centric city with symmetrically distributed radial highways converging toward the central business district (CBD), with an inelastic commuter demand. The model assumes that the congestible highway and the congestion-free monorail can be accessed at all points along the travel corridor, but travelers only exit at the CBD. We compare the aggregate travel time savings (ATTS) from different monorail scenarios, with the introduction of a toll as a necessary condition to generate an efficient outcome. The results show that for a monorail running at an average speed of 40 km/h a length of 26.3 km from the CBD will optimize investment and contribute travel time savings of 105 million Rs. per day or 189 million USD per year to the Sri Lankan economy. A sensitivity analysis is conducted to evaluate the effects of monorail speed, commuter income, social interest rate, employment density distribution, and population growth on ATTS.