The milk run revisited: A load factor paradox with economic and environmental implications for urban freight transport

Research has shown that time access restrictions in city centers might increase social sustainability aspects such as livability or safety, but might also increase the number of vehicles and the total distance travelled; which have negative environmental impact and can decrease economic sustainability. In this paper we see that this negative effect could also be the result of other access restrictions, like load factor restrictions, and may be related to factors other than the number of vehicles and total distance travelled. Such as if the distribution center is in the outskirts of the city and customers are situated outside the city center. In this study a common urban distribution network scenario is presented – the milk run – where only the load factor is changed. Increasing the load factor is usually regarded as a way of improving efficiency, but we observe that under certain conditions improving the load factor affects economic and environmental sustainability, by increasing total costs and emissions. Following insights from this study, policy makers and companies should be careful when using single key performance indicators in urban freight distribution.