Glider industry petition in support of glider trucks debunks itself

It’s not the most important or even the worst thing about the Pruitt EPA’s proposal to reverse course on closing a loophole in the emissions regulations for heavy-duty vehicles that left “gliders”—that is, a remanufactured engine in a new chassis—uncovered. But the summary of a “study” that the glider industry submitted to EPA to support its claim that the agency was wrong in the first place about how dirty gliders are is fingernails-on-a-chalkboard aggravating to us at the ICCT. It’s sketchy work presenting partial information as though it’s serious and credible technical analysis meant to honestly inform a public debate, when its real effect is to obfuscate and confuse.

We’ll have more to say about the consequences of the Pruitt EPA’s proposal. For now I just want to briefly point out why this part of justification being offered for reversing EPA’s earlier action is bogus.

The remanufactured engines used in gliders are most often what’s known as “pre-emissions”—that is, built in the 1990’s and early 2000’s, before regulation set strict limits on nitrogen oxide (NOx) and particulate matter (PM) emissions (and other pollutants) in new heavy-duty diesel engine exhaust. A decade ago there were a few hundred gliders built annually in the entire U.S., to deal with cases where something (like an accident) wrecked a truck chassis but left the powertrain usable. Today, annual sales of gliders are over 10,000 units, approximately 5% of all the Class 7 and 8 tractor sales, according to the best estimates we have, and climbing fast. The reason for that surge in sales was pretty obviously people wanting to evade the emission control standards.

So when the EPA put out Phase 2 of the HDV greenhouse gas rule, in 2014, it also limited glider sales, to ensure that the air quality and health benefits from the NOx and PM limits for heavy diesel engines were not undermined. At the time, EPA estimated that without a sales cap glider emissions would represent “about one third of all NOX and PM emissions from heavy-duty tractors in 2025.” That estimate reflected assumptions that gliders, in the absence of any restrictions, would continue to be about 5% of the heavy-duty tractor fleet and that “gliders emit at the level equivalent to the engines meeting the MY 1998–2001 standards since most glider vehicles currently being produced use remanufactured engines of this vintage.”

The glider industry’s bid to overturn the limit on sales rests in part on an argument that EPA should not have assumed that emissions from a remanufactured engine installed in a new chassis would be on par with the emissions standard from the year the engine was manufactured. And they submitted a letter from the president of Tennessee Technological University saying that a study of heavy-duty engine emissions done there purportedly cast doubt on EPA’s emissions calculations.

No complete report of this Tennessee Tech study seems to be available anywhere, so all we have to go on is the four-page summary included as an exhibit in the industry (“petitioner’s”) request to EPA. And it’s rife with unexplained claims and contradictory statements.

But the first problem is what the summary doesn’t contain, which is anything at all about the test methodology. There are two pieces of information that are always supplied when research laboratories describe a vehicle or engine emissions test, even in summary form: information on the test equipment and information on the test cycle. The Tennessee Tech summary includes neither. But apparently EPA staff did meet with Tennessee Tech staff to discuss details of the test protocol and the notes from the discussion were recently posted in the docket. The notes confirm that Tennessee Tech’s test lab was unable to measure particulate emissions from diesel engines, even those that were not equipped with any particulate filter. Tennessee Tech’s own description of their lab makes it clear that they are not anywhere close to being equipped to follow certified emissions testing protocols that have been in place for decades. And it means that the “study” doesn’t even empirically assess one of the two main harms from the explosion of glider sales that EPA intended to address—particulate matter emissions.

The EPA’s concern in Phase 2 was regarding how much NOx and PM emissions from glider trucks would increase in the absence of a sales cap. Not only was Tennessee Tech unable to measure PM emissions, the summary doesn’t report NOx emissions measurements from the “study” except to note that they ranged from 0.44 to 6.45 grams per horsepower-hour (g/HP*hr) — that is, between 2 times and 32 times the NOx limit for post-2010 engines! Not only does that not call into question EPA’s Phase 2 assumptions; it confirms them.

The summary reports in detail only carbon monoxide measurements, which EPA didn’t focus on. Apparently the Tennessee Tech “study” found no statistical difference between the CO emissions from new and remanufactured engines, which suggests that new and remanufactured engines of the same model year would have the same emissions levels—again, exactly in line with the assumptions made by EPA when calculating the potential emissions impact from glider trucks in the absence of standards.

So on the basis of a study done at an emissions testing lab that was unable to measure PM emissions, which measured NOx emissions as much as 32 times the limits in place since 2010, and which measured CO at levels that confirm the reasonableness of EPA’s assumptions concerning emissions from new and remanufactured heavy diesel engines, the glider industry argues (and the Pruitt EPA seems prepared to agree) that “glider kit HDVs would emit less than 12% of the total NOx and PM emissions” for all Class 8 HDVs, not the one-third of all NOx and PM that EPA estimated. They give zero explanation of how they came to this conclusion—no information about what glider truck sales volume they assumed, no information about what NOx and PM emissions level they assumed for the glider trucks, and even no information about what year their calculations reflect.

A number of ways come to mind to characterize that kind of technical analysis. Here let me just say that nothing presented in the Tennessee Tech letter supports the glider industry’s claim that the analysis for the Phase 2 rule was incorrect and assertion that glider trucks would emit a lower fraction of Class 8 NOx and PM emissions than EPA estimated initially. It’s disappointing to contemplate that the Pruitt EPA’s proposal to reverse that part of the Phase 2 rule could be based even in part on this sort of representation.