The Government increased the maximum gross weight of lorries from 41 tonnes to 44 tonnes in February 2001. I undertook an analysis the previous year for the Commission for Integrated Transport (CfIT) which suggested that this measure would yield 'small, but significant' economic and environmental benefits. It predicted that greater consolidation of heavy loads would yield annual savings of:

• 100 million vehicle-kms
• £60-80 million in road haulage costs (in 2000 prices)
• 80-100,000 tonnes of CO₂

I have recently assessed the actual impact of the maximum weight increase over its first three years using unpublished data from the Department for Transport. The results of this analysis were recently published in the journal Transportation Research (part D). These show that the benefits were greater than predicted.

After three years the annual savings were approximately:

• 134 million vehicle-kms
• £110 million in road haulage costs (in 2004 prices)
• 136,000 tonnes of CO₂

Analysis of the government's road freight statistics suggest that it will be around 2006-7 before the haulage industry has fully adjusted to the new weight limits. By then the annual savings will be roughly 27% higher.

Three factors have contributed to the under-estimation of the benefits:

• The government's decision to charge the same rate of vehicle excise duty for 44 tonne vehicles as for 41 and 40 tonne vehicles (with six axles). It had been anticipated that the heavier vehicles would incur a higher rate of VED.
• Much less freight than expected has switched from rail to road as a result of the increase in maximum lorry weight. This can be partly attributed to the decision of the Rail Regulator in 2001 to provide financial compensation to the rail freight sector for the increase in maximum lorry weights.
• The higher weight limit and associated reduction in road haulage costs has induced less growth in the demand for road freight services than predicted.

By the end of 2003, just over 50,000 lorries were registered at the higher weight limit They accounted for 45% of all the freight movement on Britain's roads (measured in tonne-kms).

Although the load consolidation benefits are greater than expected, many companies are, nevertheless, operating 44 tonne lorries well below capacity. The average payload on these vehicles is only 17.9 tonnes - well below the maximum load of 29 tonnes that could be carried. On only 30% of the distance that 44 tonne vehicles travel with a load are they fully laden in weight terms. On 37% of the kilometres travelled laden the load is constrained by the amount of space in the vehicle rather than by the weight limit. As the average density of freight is declining many companies would now derive more benefit from an increase in the maximum size of lorries rather than a further increase in their maximum weight.

The article concludes that:

'As the actual reduction in truck-kms is greater than predicted and the erosion of freight from rail less than expected, the estimated economic and environmental benefits quoted in the Commission's study have to be revised upwards.'

'It is, nevertheless, likely that any new proposal to increase maximum truck would be very controversial and fiercely resisted, particularly by environmental pressure groups and the rail freight industry. It would make it more difficult for the government to achieve the 80% growth target it set for rail tonne-kms in its 10 year transport plan, especially as the industrial sectors deriving greatest benefit from truck weight increases produce many of the dense, primary products that have traditionally constituted railfreight's core market.'

For further information please contact Professor Alan McKinnon, director of the Logistics Research Centre, Heriot-Watt University, EDINBURGH. EH14 4AS A.C.McKinnon@hw.ac.uk

Web site: http://www.sml.hw.ac.uk/logistics

A copy of the Commission for Integrated Transport's 2000 report on the lorry weight increase can be found at http://www.cfit.gov.uk/reports/44tonne/index.htm