The White Paper on a Common Transport Policy, published by the European Commission in September 2001, states that heavy goods vehicle traffic on European roads could increase by nearly 50% by 2010 relative to its 1998 level.
The paper outlines a number of measures to reduce the growth of road haulage to 38%. To cater even for this less pronounced rate of growth, pressure is being applied by the European road transport industry (truck and tyre manufacturers, roads authorities, etc) to address this problem through increasing the size of trucks allowed in Europe.
Specifically, there is an active interest in increasing the legal truck weight limit to 48 tonnes, consisting of six 8-tonne axles.
The objective of this proposed research is to determine the implications for Ireland's road infrastructure of the arrival of such heavier trucks on Irish roads.
The greatest financial implications are in the deterioration of road pavements – an increase in the typical number of axles from five to six could keep axle loads at existing levels. However, this assumes no illegal lifting of one axle and an even distribution of loads between axles. Research will be carried out on the mechanisms through which pavements deteriorate in response to applied axle load.
This will incorporate the alleviating effects of possible 'smart' suspension systems which the new trucks may incorporate and which could act to counter the effect of spatial repeatability. The implications of heavier trucks for Ireland's bridge stock will also be considered. A major contribution will also be made to the technology of weighing trucks in motion which has the potential to be used for automatic enforcement of legal truck weight limits.
- Probabilistic Dynamic Truck Model: A key product of the proposed research will be a heavy truck dynamic model which reflects the existing and future truck population. Many models have been developed in the past for particular trucks but what is needed to determine the implications for road infrastructure is a probabilistic model which reflects the range and frequency of the different heavy trucks on the road.
- Pavement Deterioration Model: A key goal of the proposed research is to develop a numerical model of pavement deterioration in response to applied loading. The deterioration of pavement in an actual road is complicated by the phenomenon of statistical spatial repeatability, first identified using French data by the principal investigator and the Laboratoire Central des Ponts et Chaussées (LCPC). As the road deforms, the surface profile changes and it is known that this profile controls the mean pattern of dynamic force that is applied. It is a primary objective of this project to develop an understanding of the relationship between the road profile and the mean pattern of applied force for a given distribution of traffic.
- Multiple-Sensor Weigh-in-Motion: The degree to which legal weight limits are enforced is equally as important as the limits themselves. It is well established that trucks with weights substantially in excess of the legal limits are widespread in Ireland and many other European countries.
- Bridge Traffic Loading: The development of longer and heavier trucks is likely to have significant implications for road bridges as it results in a greater concentration of weight in a shorter length of bridge. It is relatively inexpensive to design new bridges for heavier trucks (although the research to determine the extra strength required is still needed). A much more serious issue is the existing bridge stock, including heritage structures. A high frequency of heavier trucks could greatly increase the characteristic load level for existing bridges and the cost of the strengthening and replacement that could result might be exorbitant.