Factors behind Empty Transport Flows
Empty movements are one of the most significant operational and commercial constraints in transportation affecting both passengers and freight flows alike. They involve the repositioning of transport assets, which does not generate any income during the process, implying that this cost must be absorbed. For instance, about 20% of all containers are moved empty as they are being repositioned. There are four main factors explaining why several transport flows are empty:
  • Imbalanced Flows. The demand for transportation between two locations is almost never balanced, but there is a reciprocity in these imbalances. For instance, international trade relations underline that some nations import more than they export while it is the opposite for others (export-oriented economies). Similar patterns can be observed at the regional or local (urban) levels. Imbalances can also have a temporal implication, implying that while at an aggregate level flows could appear to be balanced, they can be highly imbalanced for some time periods. For instance, commuting usually involve imbalanced movements between the central area of a city and its periphery, with the dominance of inbound movements in the morning and of outbound movements in the afternoon.
  • Cargo and Equipment Specialization. Some types of cargoes can only be transported with specialized modes and equipment. Thus, even if there is cargo available for a backhaul movement the conveyance for the inbound haul may not be suitable. For instance, refrigerated vehicles and containers are not well designed to carry other types of cargo, implying that cold chain transportation usually has empty backhauls. Further, it is common in many bulk trades such as for petroleum, grains and minerals to have an empty backhaul because the ships are specialized carriers not designed to carry anything else.
  • Short Hauls. Many transport flows are over short distances and covering a specific sequence, such as feeders or local deliveries. They may thus be unable to be available for backhaul cargo opportunities that could be further away. As such, the range of transport services impose limitations in their market opportunities and the availability of backhaul flows.
  • Regulatory Constraints. Although there could be opportunities for backhaul movements, the regulatory context may prevent it. For instance, cabotage regulations prevent maritime shipping companies, airlines and trucking companies to carry cargo or passengers in many national markets. A foreign flagged shipping company cannot carry cargo between two American ports and an international airline cannot carry passengers between two American airports. In the taxi industry, a driver can only pick up customers in specific jurisdictions (e.g. a town or a city). Own account transporters (e.g. the transport branch of a large retailer) can only carry cargo for the corporation they are part of, which often results in more empty hauls.
There are limited effective mitigations to empty movements, at start because many are the outcome of macroeconomic or spatial processes that cannot be readily influenced on the short term. Trade imbalances are mainly the outcome of differences in comparative advantages such as labor costs or the availability of resources. Containerization has enabled a better mix of cargo but the large commodity trades still depend on specialized conveyances. Regulatory changes, such as cabotage restrictions, could be alleviated, but national or regional markets are usually protected by special interest groups unwilling to forego the rent seeking advantages that this implies.