DIFFERENT CARGO TYPES
A second analysis examined the trip length characteristics of different cargo types. This reveals the long-distance nature of unitised goods, in particular containers and palletised goods. The latter was perhaps less expected - two-thirds of this consignment type is on trips of over 150km. To put this in perspective, palletised goods form a third of all the distance travelled by consignments on GB vehicles.
This, of course, does not take into account size and weight or the number of pallets dropped at one or more locations, so it is not comparable to vehicle kilometres. One container, for example, may make up the entire payload of a large HGV.
M6 AND M62 ANALYSIS
While routes from ports provide an absolute concentration of origins and destinations (trip ends), and thus make the count-based analysis possible, corridors and specific points on the Strategic Road Network (SRN) need further analysis.
Hence the GB Freight Model was able to provide two contrasting points on the SRN, to undertake a supplementary analysis at key points on the network. These were: M6 (between junctions 12 and 13) to capture north/south movements; and the M62 (between junctions 21 and 22) to include shorter east/west movements.
However, a disaggregation by HGV type, identifying the largest artics, is not available at this level of the model output. In this sense, the analysis provides a conservative estimate of the concentration of trip ends, since many HGVs used for local deliveries will be captured as well as the largest used for longer-distance transport.
This effect is shown in the diagram (see opposite page). It can be seen that there are many more short-distance trips in the GBFM all HGV figure than the national figure for artics that have more than five axles.
Despite this effect, there is a very significant concentration of trip ends of all the HGVs at the sites on the SRN (origins and destinations), as shown in the two maps which follow (see above). In terms of potential impact, this concentration is used to assess the likelihood of transfer, as well as the distribution of trip length. The potential for reduction is applied to the DfT count data from the same sites, which does separate out the largest artics with five axles or more from other traffic.
The count data for the two sites is set out in the tables on the right.
Without additional data on cargo type and trip ends for artics alone, it is hard to produce a definitive transfer rate to rail. However, using the conservative distance data and the clear trip end concentrations, an estimate of the potential transfer was made and cross-checked with the rail freight operators. It was decided to use a transfer rate of 20% to see if this would achieve the threshold level of reduction. This resulted in the following reductions in the largest artics.
SUMMARY OF GBFM RESULTS
These high-level assessments show that in one instance - the M6 site - the criterion is likely to be met. On the M62 site, however, more data on cargo type is needed before ascertaining if the DfT HGV threshold will be met. Given the (as expected) shorter-length trips on the M62, it would nevertheless be worthwhile to investigate this corridor in more detail - in particular to isolate the trans-Pennine traffic and to allow for the high concentration of trip ends evident on the M62 map.
Data on cargo type would also be useful - for example, minerals are likely to be important in this corridor and would bring the heaviest rigid vehicles into play in terms of reducing HGV flows. For rail freight to compete, high volume will compensate for shorter trip lengths. Capacity issues on the parallel rail corridor (West Coast Main Line) are considered.
VEHICLES OR PASSENGER CAR UNITS
The congestion impact of the heaviest lorries is variable, depending on road conditions. The acceleration/deceleration/braking characteristics will mean much higher road space occupancy than the 2.9 passenger car units (pcus) often used. On the other hand, on an empty road, adding an extra car or articulated lorry will make no difference to the capacity of that road.
In this study, a range of three to four pcus has been used. Further work might be able to distinguish more disaggregated values by time of day. This study concentrates on the Strategic Road Network, a majority of which will have junctions designed to take larger HGVs. However, parts of the SRN - and the roads leading to the destinations of most of the HGV traffic - will not. In these circumstances the pcu value (for example, of turning articulated vehicles) can create pcu values extending to double figures.
RAIL ANALYSIS
The rail freight operators and Network Rail were consulted to establish the following:
- The likelihood and timescale for transferring the targeted traffic. What level of rail freight upgrades are needed on the rail network and what is planned by Network Rail.
- The additional network capacity required.
- How much capacity would be required in addition to existing NR plans already in the NR Freight Network Study.
- The Impact of more Strategic Rail Freight Interchanges and consolidation coming on stream. As more planned Strategic Rail Freight Interchanges become operational, there is further scope to transfer flows to rail.
- The increased capacity from smart paths (more efficient freight paths and also holding places for freight trains).
- Train lengthening and heavier trains are also taken into account.
