Trucks, road damage and road tolls

Recently I have become interested in the problem of increasing road congestion. This post is just meant to be a kind of general introduction to the issue, and also to demonstrate how damaging the increasing freight transport via trucks can become if the ensuing problems aren’t addressed properly soon. In follow-up posts the main focus will be on the situation in Europe, where complete gridlock will become inevitable if we don’t do something about current developments. I’ll also write about alternative means of transportation and new technological developments in this area. As a layman, I’d also be grateful for feedback from people who have first-hand knowledge of the industry and will incorporate it into my future posts; I’ll also be happy to correct any mistakes I have made with this one. Provided that any specialists are interested in this post post at all, I’ll very likely get quite an earful… :)
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This March, Jonathan quoted from an article by Robert Poole at the Reason Foundation’s website, Trucks and Tolling: the Drama Continues:

The trucking groups don’t seem to realize that the leasing of a few high-profile toll roads is just a small part of a much larger and more important phenomenon: the infusion of global capital into a capital-starved U.S. highway system. The multi-billion-dollar new toll road projects that keep being announced in Texas are a foretaste of what we can look forward to if we create a comparably friendly investment climate in other states.

This from further up the text also is noteworthy:

…a trucking industry coalition held a DC news conference to denounce toll road leasing. They charged that such moves burden taxpayers and could have negative impacts on safety, security and motorists. The American Trucking Associations statement even called for the goal of a toll-free national highway system…

…

It’s unfortunate that things have come to this pass, because there is much to be gained by truckers and shippers from increased use of toll finance and public-private partnerships.

There are other good reasons for public-private partnerships and toll-financing. A little known but crucial fact is that wear and tear of roads tends to increase to the fourth power when axle loads go up:

The relative damaging effect of an axle is considered to be approximately proportional to the fourth power of the load [1, 30]. However, this has been found to be an under-estimate for flexible pavements on weak subgrades such as peat [3, 23], where damage has been found to be proportional to the sixth power and higher.

In other words, a 40 ton truck can easily cause as much damage to a typical road as 60,000 1 ton cars. The fourth power rule isn’t carved in stone, of course, but it happens to describe damage to roads most accurately. Factors that influence the concrete amount of damage a road suffers are besides subgrades the tires and the paving materials and their specific (di-)stress modes (Link to a 114 kb PDF-File). Distress modes of road pavement include damages such as surface cracking, surface roughness and rutting.

Regardless of the details, the disparity of the damage caused by trucks compared to passenger cars demonstrates that a highway system without at least some charges on trucks is the equivalent of a hefty subsidy for trucking businesses road repairs are paid for by taxpayers in general, while truck owners aren’t paying more than anyone else. Trucks are indispensable for transporting the goods that industry and consumers depend on, so a certain amount of subsidies may be unavoidable, but it should at the very least be transparent to what extent the trucking firms are supported. After all, given a cash-starved highway system, a category that includes pretty much any purely state owned system, a refusal to collect tolls will lead to a gradual decay of the infrastructure, increasing gridlock and more roadworks with further slowdown of traffic in general.

As the article at Reason Foundation points out, freight transportation is increasing even more rapidly than passenger transportation, with a severe capacity crunch not to far in the future. It may therefore be worthwhile to separate cars from trucks along major roadways and trucking firms should be happy to pay for them, as a transportation consultant Poole is quoting puts it.

The advantages of special toll roads for trucks fortunately go beyond the infusion of global capital and additional capacity for freight transportation. If constructed and operated by private businesses with a minimum of government intervention, the operators will have strong incentives to use subgrades and road materials that are able to withstand damage from heavy trucks to a greater extent than usual, thereby reducing cost for repairs, traffic jams and increasing the general throughput of heavy vehicles, compared to conventional highways. After all, deviations from optimal throughput would have a direct impact on the operator’s bottom line. Private operators also could in turn offer incentives to trucking businesses, by offering to reduce toll charges if they use tires and axle loads (by efficient distribution of freight loads in the hold, for example, or even longer trucks with more axles) that will reduce damage to road surfaces. In case of strong government intervention, these advantages would be diminished for the dilution of direct responsibility also would reduce the incentive to minimize damage to the highway system.

With government intervention or not, in the long run toll roads won’t be a sufficient solution to traffic congestion, let alone road damage. As already mentioned above, the amount of freight transportation is increasing rapidly and the proposed toll roads for trucks would accelerate he process. Trucking firms may oppose them now, but as soon as they realize just how advantageous special toll roads are for them, they will feel encouraged to buy even more trucks than they would have anyhow. In response to this, the highway system and especially the toll roads can be extended some more, but there are obvious limits, such as bottlenecks where additional roads cannot be build or the NIMBY factor preventing any construction at all. At some point, road tolls will have to be charged not just to finance the construction and mending of roads, but also to allocate traffic to less frequented roads, preferably via an electronic traffic control system that can react flexibly to changing traffic patterns and congestion. This especially goes for Europe, where relatively little room is left for additional roads, and the widening of bottlenecks frequently involves digging tunnels that are five or more miles long. Capacity already is scarce enough that congestion in one country will make itself felt in several more, especially if a major road artery is involved.

Even given maximum possible extent of the highway system and optimum utilization of its capacity, at some point it will become necessary to change the economics of the transport business itself, as well as the basis on which their principals calculate loads. Just-in-time delivery that turns the cargo holds of trucks into rolling inventories saves industry a lot of money and increases flexibility, but it also puts serious costs and burdens onto the general public. If those were even just partially priced into the tolls for trucks, it would pay to add storage holds to production facilities and cut back on the number of trucks put to use. Freights also will need to be shifted to other means of transportation, such as trains and also ships, where navigable rivers make it practicable.

There is no panacea, though. Rail systems also suffers from damage that increases in the fourth power as axle loads increase. Additionally, marshaling yards take up a lot of acreage and won’t be all that popular with the neighbors, so the NIMBY factor also applies here.

So far with this post. In some follow-up posts I’ll address congestion caused by passenger cars and what to do about it. I also have some ideas I’d like to flog on how new technologies and free-market approaches might help to defuse existing problems and minimize future ones. Like I wrote above, I’ll gladly address any feedback I get.