Following two full days of comparative trials - run by the British Transport Advisory Committee (BTAC) at the Motor Industry Research Association test track - results indicate that the use of larger commercial vehicles can have a positive impact on fuel usage.

Transport Press Services (TPS) reports that much focus was put on packaging of goods and their assembly into standard-size units. With the pressure on to move more goods quicker many trucks are running out of space. Consequently they frequently run inefficiently short of their weight-carrying capability, the load having split onto a second vehicle.

The BTAC trials highlighted the point during part-load tests of three articulated trucks, two of which were experimental designs, longer than usual. The trucks were subjected to the 'crisps test', because they carried loads that simulated the density of pallets stacked with packets of potato crisps.

The trial showed that by measure of cubic capacity there is a fuel efficiency gain of 9.5 per cent with a semi-trailer 16 instead of 13.6 metres interior length, and 15.66 per cent gain with a 25.25-metre, B-train combination of articulated double semi-trailers (a total interior length of 21.4 metres).

In terms of taking pallets with no waste of space the efficiency of the 16m semi-trailer proved ideal. The extra 2.5-metre length increase over present regulations allow it improved pallet transport productivity figures of between 15 and 18.75 per cent. Its interior can be filled completely with either 40 europallets or 32 imperial pallets. Of course, the longer the vehicle the greater its cubic capacity and the consequent quantity of goods that can be moved for a given quantity of fuel.

The 25.25-metre B-train, with a 7.8-metre body on its leading semi-trailer and 13.6-metre on its second semi-trailer brings a drop in fuel usage per cubic metre of 15.66 per cent and raises pallet numbers per trip by between 39.5 and 43 per cent. Its
development - based on the European modular concept - is being financed by Lincolnshire haulier Denby Transport.

Beyond that, Staffordshire haulier Stan Robinson brought to the BTAC trials an articulated truck towing a trailer – doubling the standard artic load capacity. That brings a prospect of halving the number of lorries to move a given amount of freight. Fuel consumption per ton moved is slashed to about a litre, which
is an improvement of nearly a third over current articulated 44-tonners.

The Robinson camp acknowledges nervousness about 31-metre long lorries, but points out their economic and environmental values even if restricted to special-licence duties. An example of the future potential would be shunting of containers between the proposed London Gateway deep-sea port and a holding depot close to the M25. Concerns have been raised in Essex about the
lorry traffic that the new port might create. Such traffic across the county would plunge if there were two-at-a-time container movements.

Operators at the BTAC trials championed a rational approach to removing concern about increase in length: to legislate on the basis of manoeuvrability. To establish the credentials of this basis the BTAC trials included turn-circle tests to compare the longer vehicles’ manoeuvrability with the legislated requirement to stay within a circular corridor formed by radiuses of 12.5 and 5.3 metres. This can just be met by current top-size articulated lorries. The double articulated Denby B-train met it with over a
foot to spare. The Morrisons artic with the self-steering Don-Bur 16-metre trailer did it with 2.4 metres to spare. A Scania tractor with steering tag axle took the B-train around the circle three-quarters of a metre tighter than when it was hauled by a tractor with a steering axle.

Many other tests were included in the BTAC trials in the drive to grasp any straws in the interest of saving massively expensive fuel.

Britain’s biggest freight-transport company, Exel, assessed the worth of fitting a streamlining air deflector to the cab-roof of a Daf coupled to a Hovis flour tanker at 43 tonnes. There was no significant improvement at 60km/h but nearly 11 per cent saving of fuel at 90 km/h (from 7.3 to 8.1 miles per gallon).

Big tyre remoulder Bandvulc, from Devon, evaluated the benefit of an easy-roll compound that it has developed. Compared with the popular Michelin of the same tread depth there was nearly 5 per cent saving in fuel consumption.

Results of two experiments with re-mapping the electronics of engine management suggested variable judgment on the worth, dependent on the relation of available power to the operation’s power demand. When a 380hp Scania was re-mapped to 436hp the fuel consumption was only half a per cent worse. A Scania V8 uprated to 718hp produced fuel consumption 8 per cent worse than the 480hp Scania evaluated in last year’s trials but 2.2 per cent better than the 530hp MAN that hauled Stan Robinson’s combinations.

Assuming the declared powers were correct, it seems fair to judge that, with a greater proportion of work at part load, the fuel-economy penalty of between 15 and 20 per cent extra maximum power is quite small.

The Royal Mail evaluated the fuel consumption effect there will be when a European Union directive forces 90 km/h speed limiters on commercial vehicles grossing more than 3.5 tonnes (12 tonnes at present).

Figures after exchanging drivers between two Daf box vans grossing 5.36 tonnes indicated that at a steady 56mph the fuel consumption was nearly 19 per cent better than at a steady 70mph. The extent to which longer journey times will bring a need for more vehicles to move the mail has yet to be
experienced.

Another test of the two Dafs to test the claims of IFED, Watford, for a magnetic sleeved stick of platinum coated ceramic beads in the fuel tank could not prove a significant improvement. The fuel consumption figures indicated an average 0.2 per cent overall improvement, but the average speed was 5 per cent lower.

In another comparison, which at 3.6 tonnes pitted an automatic gearchange against a manual gearchange in two 3.5-tonne Iveco Daily vans, the Royal Mail tests showed a 6 per cent improvement in favour of automatic control.

To what extent does tyre pressure affect the fuel consumptions of a 2.8-tonne gross van? British Telecommunications did tests with the tyres under-inflated by 20 per cent and over-inflated by 20 per cent. The most reliable of the results, obtained on multi-stop simulation, revealed a 2.4 per cent better economy with hard tyres and 2.4 per cent worse with soft tyres.

For more information on the BTAC trials and ways to save fuel don't miss the November isue of ROADWAY - out October 22.