Trucks: the road to ruin or increased efficiency?

Directorate for Science, Technology and Industry

Ruairi O Brien

How can freight trucks be made heavier and still reduce road damage and cut transport costs? The answer may be divine. 

Road maintenance is a huge public cost in most industrial countries. In fact, it can represent as much as three quarters of the total road infrastructure budget in some of them. One of the challenges for governments is how to improve efficiency in the administration of road expenditures to keep those costs under control, while achieving greater efficiency in road transport.

Freight traffic is the main cause of road damage, which is why most of the debate has focused on heavy trucks. In fact, with engineering advances transport efficiency can be improved. It is even possible to allow an increase in heavy vehicle mass limits for vehicles using advanced suspension technology without causing an increase in road damage costs. Moreover, the increase in efficiency could provide end users with lower transport costs.

Over 70% of freight travels by road transport at some point from production to final consumer. For the period 1975-95, the volume of road freight (tonne-kilometres) increased in OECD countries, see figure for growth rates in the United States, European Union and Japan. Countries with particularly high growth rates between 1980 and mid 90s include Australia (119%), Korea (288%) and Turkey (229%).

Given the importance of transport to the economy – the asset value of a road network averages one and a half to three times annual GNP in OECD countries – it is not surprising that government investment in transport infrastructure is big business. Take for example the 1998 United States Transportation Equity Act: US$198 billion to be invested in rebuilding the US transportation system over six years. That’s more than the GDP of Sweden in the same year. Maintenance and rehabilitation account for the lion’s share of annual road budgets in many OECD countries, since their major transport infrastructure is already in place. New construction can account for as little as 10% of the total infrastructure budget.

Divine Design

Various aspects of vehicle design have been improved to reduce pavement damage during the last 40 years or more, suspension performance being one of them. The extent of the progress has not been lost on the regulators. The European Commission, for instance, has introduced preferential weight limits for certain vehicles with “road-friendly” air or equivalent suspensions. Knowledge of the scientific and economic benefits of these air suspensions was very limited until comprehensive experiments were carried out through the OECD Programme of Research on Road Transport and Intermodal Linkages. The results of this study have been rather appropriately called DIVINE, which stands for Dynamic Interaction between Vehicles and Infrastructure Experiment. They will have important implications for future road construction and maintenance, as well as for suspension standards.

The potential economic benefits are broadly twofold. First, replacing the national fleet with road-friendly vehicles could considerably reduce maintenance and rehabilitation costs. OECD research estimates that road-friendly suspensions could increase pavement life by between 15% and 60%, depending on the pavement. That’s a considerable saving.

Second, by increasing the weight limits for road-friendly vehicles, transport efficiency is improved without increasing road wear. The National Road Transport Commission in Australia estimates that a 15% increase in vehicle mass limits would generate savings of AUS$840 million (or US$535 million) per year in transport costs. As a result, higher mass limits were introduced on the National Highway System in Australia last year for vehicles fitted with road-friendly suspensions. These two options are of course not mutually exclusive and countries will want to set their own mass limits to fit in with their overall transport policies.

One of the problems about the heavier trucks with the new suspension is that many bridges would have to be upgraded. That is a significant and costly task. However, when carried out in conjunction with general maintenance and rehabilitation programmes, the savings in transport costs should outweigh the additional bridge-related expenditure in the longer term.

Transport operators and governments are not the only ones to benefit from the efficiency gains; the wider economy should as well. And improving the productivity of road freight transport through a more strategic and efficient management of the road network could benefit road safety and the environment too, particularly if improved technology leads to a reduction in the number of freight vehicles on the roads.

Policymakers could consider several options. They can make mandatory requirements for heavy vehicle suspension systems to become more road-friendly. They can use price incentives to encourage the uptake of road-friendly suspensions by transport operators. And they could use operational incentives, such as allowing increases in gross vehicle mass limits for vehicles with road-friendly suspensions. The choice of approach is theirs. The benefits would be everybody’s.

©OECD Observer No 220, April 2000

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