This paper presents a modelling approach for the simulation of supply chains including last mile delivery by using approximations. A brief introduction to the most common approximation metrics for distance calculations and their applications within the context of simulation is given. A practical example for the calculation of distances is presented using a discrete-event simulation model. By comparing different distance metrics with the real distances on an exemplary supply chain, it can be determined whether a satisfactory distance metric exists for calculating distances in urban areas, without the integration of an external route planning web service.