I noticed a lot of interest on the “truck ban” scheme from the statistics provided by WordPress on my dashboard. It seems there are very limited material available on the scheme especially in the Philippines where there have been variations of and misconceptions on this travel demand management (TDM) measure. Why do cities like Metro Manila implement a truck ban? Or better yet, why are there designated truck routes in cities? The answer can be quite simple if viewed from the perspective of asset preservation. That is, by restricting trucks to use specific roads, we are also limiting their impacts (read: damage) to the road infrastructure. Such impacts come in the way of damaged pavements and/or bridges that bear the brunt of the weights carried by heavy vehicles. But such argument begs the question of why, in the first place, shouldn’t we design our pavements and bridges so that they may be able to withstand the cumulative loads of heavy vehicle traffic over a prescribed period of time, say 20 years, give and take a few years for variability and reliability in design and construction methods? Such is a question that needs to be answered, and clearly, by our DPWH, at least for the case of our national roads and bridges. It is really not a simple matter and certainly not something that cannot be blamed solely on the fact that evidences in the Philippines point to truck overloading as one of the culprits for damaged pavements and bridges.
The website of the Department of Public Works and Highways provides information on the axle load and truck weight limits for national roads. The matrix of weights may easily be downloaded and is provided in the following document:
The maximum single axle loads for different countries around the world are provided below:
I found another table of values this time for European countries. Based on the table on weight limits in European Union Countries, France seems to have the heaviest single axle load limit.
Still, the question running in the minds of most people involved in policymaking, monitoring and enforcement, and research is “How did we come up with the 13.5-metric ton maximum single axle load value in the first place?” Surely, it wasn’t a number that was plucked out from the air?
The 13.5-metric ton was most probably derived from an axle load study conducted in the 1990’s. Such a study could have, among others, determined the appropriate maximum axle loads that could be adopted by the country in lieu of the limits at the time that were already deemed obsolete given the evolution of trucks over time (i.e., they’re bigger now compared to, say, 30 years ago). What is problematic is that it seems the study was only able to derive the maximum single axle load and was not able to estimate maximum loads for tandem and tridem axles. Tandem axles are two axles positioned one after the other while tridems are three axles grouped together. These tandems and tridems are typical configurations for the rear axles of large trucks and trailers, enabling them to support heavy loads that typically are distributed more towards the rear axles.