In this article, we investigate performance of the 21 bus routes of Kolkata, an urban city in India with the help of a Variable return to scale semi-oriented radial measure based modified data envelopment analysis (DEA) model. Existing scholarly works indicate that the route based performance evaluation in the context of urban bus transport is not provided enough attention. This paper shows context specific implementation of an advanced DEA model to capture both financial and operational efficiency. Conventional BCC-DEA model shows the limitation to handle data that take both positive and negative values due its non-negativity assumption of the inputs and the outputs. The proposed model overcomes this and presents an improved measure in case of financial performance measurement. Also, the model facilitates service efficiency measurement consistent with the conventional method. Our model recognizes route specific cost advantage or service efficiency in a better way compared to the conventional model for the loss-making routes or the routes operating at a break- even level. We extend our analysis into the bus route characteristics and explore that the extent of overlapping routes, reduction of road congestion, the proper workforce allocation, and the revision of the bus fare should be given utmost priority.