Document Type

Conference Proceeding

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Freight transportation -- Mathematical models, Traffic congestion -- Economic aspects


Congestion is a common phenomenon in all major cities of the world. Increased travel time and uncertainty brought about by congestion impacts the efficiency of logistics operations. Recent studies indicate that a significant proportion of commercial vehicle kilometers traveled (VKT) and vehicle hours traveled (VHT) are generated by trip-chains or multi-stop tours. This paper presents research demonstrating the impact of congestion on multi-stop tours in urban areas. An analytical model, numerical experiments, and real-world tour data are used to understand the impact of congestion on tour characteristics, carriers? costs, VKT, and VHT. This research shows that travel time/distance between customer and depot is a crucial factor that exacerbates the negative impacts of congestion. Travel time variability is not as significant when the travel time between the depot and the customers is small in relation to the maximum tour duration and when the routes are not highly constrained. As congestion increases, the number of vehicles needed to complete the tour also increases. This is accompanied by an increase in the percentage of total driving time and the average distance travelled per customer. Congestion impacts on carriers? costs are also considerable since congestion not only increases carriers? operating costs but also affects carriers? cost structure. As congestion worsens the relative weight of labor costs ? wages and overtime ? escalates. This paper categorizes tours into three classes based on tour efficiency and the relative weight of time and distance related costs. These are intuitive and valuable tools to monitor congestion, represent real-world tour data, and classify tours in regards to their sensitivity to congestion.


Proceedings 2nd Annual National Urban Freight Conference, Long Beach, CA. December, 2007.

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