The Development of the LEFT2 Model

Abstract

Construction of the LEeds Freight Transport Model (LEFT) series was begun as part of the ITeLS project, although other funding has helped and will take forward its development. The initial version, now referred to by us as LEFT1, was a simple mode split model intended to give a rough idea of the magnitudes of the effects of various scenarios, possibly as a way of filtering which scenarios might be investigated using more detailed models. Besides being limited to mode split, LEFT1 suffered from a range of minor defects and deficiencies which led to its abandonment in favour of its successor, LEFT2. LEFT2 was constructed in 2004 as part of the Engineering and Physical Sciences Research Council LINK FIT project, ITeLS, funded by the Department for Transport (DfT). We acknowledge here the help and useful comments from many persons associated with that project. Besides mode split effects, LEFT2 allows scenarios to alter the total size of the (road plus rail) market. Its purpose is to provide instantaneous ballpark estimates of road and rail freight tonne kilometres under various ‘scenarios’. At its base is a desire that the scenarios should not affect the sum of tonnes moved by both road and rail modes. This was because we felt that our scenarios should be viewed as having a neutral macroeconomic effect. For example, if taxes on lorry usage were increased, we would expect other taxes to be lower than otherwise (or government spending to increase) so that total demand in the economy would not change. Consumers might buy their goods from closer sources than hitherto, but they would not be expected to consume less in total. For example, if prices of some goods rose slightly due to higher road user charges, the consumer would have more to spend due to offsetting reduced income tax (or whatever) and much the same total quantity would be bought. Similarly, industrialists as a whole might find input prices increasing slightly, but will find they can charge slightly more for their outputs. In summary, LEFT2 provides an instantaneous estimate of the effect of macroeconomically neutral scenarios on mode split (road, trainload and wagonload), average length of haul and total market size. LEFT2 does not load the traffic onto vehicles, and so does not produce magnitudes of HGV vehicle kilometres, for instance. Consequently it does not produce estimates of emissions or other nuisances. It is hoped that a future version of LEFT can incorporate these elements and revisit the other matters that have had to be ‘parked’ for the present. LEFT2 gives a quick idea of the magnitudes of the effects of any policies that might be considered and should help to provide a first sift where many policies are being considered. This report describes the basic LEFT Methodology in Section 2. Emphasis is given to that methodology actually embodied in LEFT2, but there is also some discussion of rejected 4 methodologies, and some that have had to be held over for later versions of LEFT. Section 3 presents additional data that was needed by the LEFT2 model. Section 4 describes the scenarios chosen for testing in the ITeLS project, while section 5 gives the first results from using the LEFT2 model, for those scenarios