Semi trucks are a common sight on American roadways, crossing the country, delivering goods quickly.

However, they’re actually a huge problem for our economy. They put tremendous strain on our infrastructure (and they don’t pay their way for their damage to our infrastructure), they’re inefficient compared to trains, and they present a serious safety risk to car traffic.

In my opinion, long haul trucking activity in the US should be extremely reduced. Read on for why that is the case.

Infrastructure strain

Semi trucks place a significant amount of strain on our highway infrastructure, even more than their weight would indicate. A common figure is that the additional damage a heavy vehicle does to a roadway, relative to another lighter vehicle, is the fourth power of the per-axle weight difference – that figure being determined by a 1962 study performed by the American Association of State Highway Officials (now the American Association of State Highway and Transportation Officials).

Road infrastructure in the US is largely paid for by fuel taxes, which is a system that rewards fuel efficient vehicles, and penalizes inefficient vehicles. According to NACS, gasoline is taxed at 48.1 cents per US gallon on average, and diesel is taxed at 53.1 cents per US gallon on average, as of January 2011. However, that taxation method does almost nothing to address the additional road wear of an extremely heavy vehicle.

According to the Lawrence Livermore National Laboratory, the average fuel efficiency of a semi truck in the US is 6 miles per US gallon – as it runs diesel, that means that a semi truck’s owner pays, on average, 8.85 cents per mile in road taxes. A semi truck can weigh up to 80,000 pounds by federal standards (more by some state standards).

In comparison, the average personal car/truck in the US, as of a 2009 EPA report (link to NYT article), got 22.4 miles per US gallon, while weighing in at 3917 pounds. As the percentage of diesels is practically a rounding error, we’ll assume gasoline, which would mean that the average vehicle driver is paying 2.15 cents per mile in road taxes – so the semi driver pays about 4.12 times more taxes.

Let’s see just how fair that is, then. First, we’ll normalize the per-axle weight, assuming that the semi has five axles, and the car has two. That means that the truck’s per-axle weight is 16000 lbs, and the car’s per axle weight is 1958.5 pounds. Without even bringing the fourth power rule into play, the semi should pay 8.17 times the taxes of the car – in other words, the semi is paying just under half of what a linear weight taxation rule would require.

With the fourth power rule, however, that becomes 4454 times the road damage. Assuming that the car were being taxed at a fair rate (it isn’t – it’s partially subsidizing the semi), that would mean that the semi’s owner would need to pay a whopping $95.77 per mile. Obviously, I’m not calling for that level of taxation, but that should be a clear indication that our road tax policy has gone horribly wrong. (Also, before you say that taxing long haul trucking at an appropriate rate relative to cars would reduce revenue, it would also reduce road damage and therefore road maintenance expenses by a similar amount. I feel that the road tax policy should be set to reflect the actual damage that extremely heavy vehicles cause, and should be set with targets of maintaining all of our road infrastructure in good condition, rather than the often crumbling condition it’s currently in.)

Efficiency

So, I’ve touched on the efficiency of a long haul truck – 6 mpg average, and 80,000 lbs maximum total weight – but I haven’t discussed the actual efficiency of hauling cargo with such a truck.

Finding exact numbers for the weight of the tractor and empty trailer is proving difficult, but it appears to be in the 30,000 pound ballpark, leaving 50,000 pounds, or 25 tons, for cargo. This means that a semi gets approximately 150 ton-miles per gallon – and some numbers I’m finding for that figure are lower.

Meanwhile, trains got 480 ton-miles per gallon in 2009, or over 3 times the cargo carried per gallon of fuel, which is a HUGE efficiency gain. To put it into perspective, the US Bureau of Transportation Statistics reported that in 2003, inter-city trucks were responsible for 1.264 trillion ton-miles of cargo transported, versus 1.551 trillion ton-miles for rail. If all of that load were transported via rail, 5.79 billion gallons of diesel fuel, or approximately 643 million barrels of oil (based on 9 gallons of distillate fuel oil per barrel) would be saved – about 67 days worth of the foreign oil imported in 2003.

Safety

According to a Maritime Administration document promoting shipping by barge over rail and truck, trucking has approximately 6.8 times more fatalities per ton-mile, and 17.3 times more injuries per ton-mile than rail. (In turn, rail has approximately 22.7 times more fataties and 125.2 times more injuries than inland marine transportation.)

Rail separates heavy cargo from light vehicles, whereas trucking mixes them up, greatly increasing the risk of death for car occupants (not to mention cyclists) sharing the road with trucks.

Conclusion

While I do feel that trucking has its place – it can handle small-load, point-to-point transportation better than rail can – I feel that we, as a country, need to heavily invest in rail infrastructure for high-speed long-haul transportation, as well as other efficient methods of long-haul transportation, and correct our road taxation to reflect the damage that heavy vehicles do to our roads. The resulting reduction in road damage and fuel expenditure will strengthen our economy significantly.