This indicator is essentially a measure of productivity, and as such, generally presents the trucking industry in a favourable light. Over the last half century in the UK there has been a five-fold increase in the number of tonne-kms carried annually by the average truck (Figure 9.1), owing mainly to increases in maximum truck weight and the use of vehicles for more hours in the day (McKinnon, 2007). Since the late 1990s this metric has levelled off for the UK truck fleet, despite two increases in the maximum truck weight since 1999 (DfT, 2008b). It is a rather poor measure of the sustainability of the road freight sector as it gives no indication of the proportion of vehicle capacity actually utilized or the potential to raise load factors.
Weight-based lading factor
This measure is exclusively weight based and is generally expressed as the ratio of the actual goods moved to the maximum tonne-kilometres achievable if the vehicles, whenever loaded, were loaded to their maximum carrying capacity (DfT, 2008b). It gives a less favourable impression of capacity utilization in the road freight industry. In the UK, for example, average load factors have declined from 63 per cent in 1990 to 57 per cent in 2007 (DfT, 2008b). Much of this reduction has, however, occurred since 1999 when maximum lorry weight was increased initially from 38 to 41 tonnes (on six axles) and then to 44 tonnes in 2001. These increases in maximum carrying capacity occur overnight, but it can then take several years for industry to adapt its ordering patterns to exploit this additional capacity. In the meantime, the average percentage load factor can drop. The recent decline in this lading factor can also be partly attributed to a decline in the average density of road freight, due to a switch from heavier materials such as metal and wood, to lighter plastics, and an increase in the amount of packaging. This increases the proportion of loads that cube-out before they weigh-out and is reflected in a decline in the weight-based measures of vehicle lading. For lower density products, space-related measures of lading are more appropriate.
Space-utilization vehicle fill
Vehicle fill can be measured in three dimensions by the percentage of space occupied by a load or in two dimensions by the proportion of the floor (or deck) area covered. In the case of unitized loads (of, for example, pallets, roll cages or stillages), the actual number of units carried can be divided by the maximum number to calculate the percentage fill. This should be accompanied by an assessment of the internal loading of the units and the average height of the pallet-loads (Samuelsson and Tilanus, 1997). There is no systematic collection of volumetric data for road freight flows, so assessing vehicle fill at an industry level is very problematic. The Transport KPI surveys commissioned by the UK government over the past decade have become a useful source of this data (McKinnon, 2007).
Empty running
Empty running is generally expressed as the proportion of vehicle-kms run empty. It is an inevitable consequence of the uni-directional movement of freight consignments and difficulty of balancing freight flows in opposite directions. Usually the final leg of a multi-drop journey, or the initial leg in a multiple collection round, is also run empty. Within the EU, the empty-running of trucks varies considerably by country and averages around 27 per cent (Eurostat, 2007). The level of empty running tends to be inversely proportional to the length of haul, because the longer the journey the greater the economic incentive to find a backload.
Empty journeys are not only wasteful economically, but also carry an environmental penalty. Encouragingly, over the last 30 years the proportion of empty running by trucks in the UK has steadily declined, yielding significant economic and environmental benefits. McKinnon and Ge (2004) estimated that other things being equal, if the percentage of empty running had remained at its 1973 level, road haulage costs in 2003 would have been £1.3 bn higher and an extra 1.1 million of tonnes of CO2 would have been emitted into the atmosphere by trucks.
