Impacts of increased vehicle weights on structures and pavements


In this project ROD-IS were commissioned by the Irish National Roads Authority (NRA) to investigate the implications of amending the Road Traffic (Construction and Use of Vehicles) Regulations (S.I 5/2003, as amended)  with respect to permitted vehicle weights for (i) the safety of bridges and (ii) for pavement life. Initially, the implications of the current legislation on general road bridges, masonry arch bridges and pavement life was assessed and subsequently, cumulative increases in the GVW were considered to assess if, and by how many tonnes, weights may be increased.


Codified load models were compared against actual site specific data obtained from a UK WIM database of approximately 2.8 million Heavy Commercial Vehicle (HCV) records (where a HCV is regarded as any vehicle weighing more than 3.5 tonnes). Initially the WIM data was cleaned to remove any suspect records and subsequent sensitivity analyses, flow scenario simulations (jammed and free flowing traffic) and long run simulations were carried out to assess if scope exists for weight limit increases on bridges. For pavements a fourth power law relationship was used to examine the potential increase in pavement wear as a result of increasing regulated HCV weight limits.