Clean air and a strong supply chain: Finding common ground in trucking

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Updated Oct 25, 2023

Everyone is familiar with the Chinese proverb “a journey of a thousand miles begins with a single step." The rest of the story, according to a Google search, is that it takes over 2 million steps to complete that thousand-mile journey. There is no avoiding the rest of the steps, although that is exactly what environmental regulators are trying to do right now. Current regulatory proposals and discussions are attempting to ignore time-proven, necessary developmental paths, and jump straight to the final destination: zero emissions vehicles. 

Regrettably, the trucking industry’s developmental path to emissions reductions is not widely understood or celebrated. This journey really got serious in the late 1990s and continues today. The focus historically has been placed on Nitrogen Oxide (NOx) and Particulate Matter (PM) emissions. More recently, with much of the world focused on climate change, the focus has shifted towards Carbon Dioxide (CO2) and other Greenhouse Gasses (GHG). 

If we review what the industry has actually accomplished over the past few decades, working in partnership with environmental regulators, we find some incredible accomplishments. In the past 20 years, the industry has reduced NOx emissions by 95% (4g/HP-hr to 0.2g/HP-hr). By 2027, NOx emissions will drop an additional 83%. When combined, these reductions represent a drop of over 99% in NOx emissions. In other words, we will have virtually eliminated NOx.  Remember that number, because we will need to come back to this. PM emissions have a similar story. As in industry, we have reduced PM emissions by 99%, the biggest step coming in 2007 with the addition of the diesel particulate filter. Again, an emissions component that we have virtually eliminated. To understand CO2 emissions, we need to recognize that CO2 emissions are directly tied to fuel economy. Over the past 20 years, the truckload industry has gone from fuel economy that averaged around 6 miles per gallon, to more fuel-efficient tractors that regularly top 7.5 miles per gallon. This conservative difference yields a CO2 emissions improvement of 25%. Strong progress. You could even argue that the CO2 and fuel economy improvements are greater, but at a minimum, these results are directionally accurate.

The improvements in the three primary emissions were won through hard-fought incremental improvements in aerodynamics, rolling resistance, diesel combustion efficiency, emissions aftertreatment and exhaust gas recirculation, among other strategies. The implementation of some of these technologies was a little painful, but we figured it out together. We worked together to bring about solid results.

Fast forward to today, and the industry is being asked to abandon this hard-fought development path, and fast forward all the way to zero-emissions vehicles (even though they are not truly zero emissions, but that is a conversation for a different day). Let’s be clear: if zero emissions vehicles were a functionally and economically viable option, we would embrace them.

Who wouldn’t want a tractor that gets the job done and has zero impact on the environment? In the current state of development, these zero emissions vehicles have some work to do before they become viable for the greater portion of freight transportation in this country. There are well documented challenges associated with the current offerings including cost, weight, range limitations, charging/fueling infrastructure, and the readiness of the nation’s electrical grid.

Again, we would embrace these technologies if not for some of these significant hurdles that still need to be overcome. If we just say no to zero emissions vehicles, then we aren’t considered part of the solution and are at risk of being left out of the discussion. 

Fortunately, we do have viable solutions.


This will be unpopular in the minds of environmentalists, but the fact is that there is still a path for diesel. Diesel fuel is an energy-packed dynamo that has served the industry well for many decades. We have already effectively reduced NOx and PM using diesel technologies. When we look at CO2, there is a clear continued path for significant reductions. These reductions would come partly through continued improvements in engine efficiency. But they would also come from the fuel itself. Progress is being made in the production of renewable diesel, with some manufacturers documenting up to a 75% reduction in GHG emissions, which includes CO2. This is not the blended biodiesel that many are familiar with, but this is pure wizardry in chemistry that reorganizes molecules to reshape organic material into diesel fuel. This is a very compelling technology to watch. Many fleets are already running some of this fuel and may not even know it. Truck stops have begun blending this new fuel with traditional diesel and are offering it at the pump today.

Renewable Natural Gas (RNG)

RNG actually boasts a negative carbon score. This is achieved as manufacturers repurpose organic material that otherwise would erode and create gasses that are harmful to the atmosphere. Instead of allowing this decomposition to impact the atmosphere, these gasses are captured and used as fuel (think cow manure and landfills). At one point in the past, natural gas was the hottest thing on the planet. It then faded from the spotlight when diesel fuel costs dropped and fleets were unwilling to deal with some of the nuances associated with the fuel. Taking another look at it today, a new 15-liter natural gas engine has just been released, diesel fuel prices are sky high, and as an alternative to electric, this technology continues to hold promise.


The description hybrid can mean a lot of different things. This could be a diesel-electric, or some other form. The interesting thing about hybrids is that you can go fully electric within a geofenced area (i.e. an environmentally sensitive area like the Port of Los Angeles), and then go back to a clean burning diesel when you leave that area. Hybrids potentially solve several of the issues that plague the electric only version for the trucking industry. It is interesting to watch the auto manufacturer’s experience in the process of converting to electric cars. They are starting to talk openly about the consumer’s acceptance of hybrids over pure electric vehicles. Consumers appreciate the flexibility of hybrids. This is one of the biggest hurdles associated with heavy duty electric tractors... the lack of flexibility. Hybrids are a natural solution to consider.

Emissions reductions via fleet replacement

At the American Trucking Associations MC&E in Austin, ATA President Chris Spear walked through some interesting data. He noted that roughly half of the tractors operating in California are equipped with 2010 model year engines or older. By replacing a pre-2010 emissions tractor with a new tractor, the calculated emissions reductions amount to a whopping 83%. That is significant and cannot be ignored. It should also be noted that the replacement tractor contains a diesel engine. Normally when we review proposed emissions regulations, we compare the new proposed emissions to the current emissions standard on new tractors. But, if there was an effective effort to replace the oldest tractors on the roads today, the benefits would skyrocket. This might require redirecting federal funds to be used in offsetting the impact of the early retirement of these tractors. But the shift would yield real and meaningful results on a much shorter timeline. An interesting alternative option.

So why are these options not being pursued by regulators? California has privately given an interesting response: they don’t want to consider the first three options in large part due to trace amounts of NOx. Remember when we reviewed the 99%-plus reduction in NOx?  They are still concerned about NOx, which doesn’t make sense. So instead of achieving immediate and substantial emissions reductions by continuing along the developmental path that has served everyone so well, California has unilaterally rejected these options. Like many issues that have become politicized, emissions reductions are being relegated to idealistic "perfect or nothing" gridlock that has made it almost impossible to get anything accomplished in today’s government. 

Organizations such as the Truckload Carriers Association and the Clean Freight Coalition have been ready to talk about sensible options on realistic timelines.   We all want clean air and water. We also want to preserve the integrity of the supply chain. In this case, we can do both. We will continue to advocate on behalf of the industry and hopefully get that done.

Dave Williams the Senior Vice President of Equipment and Government Relations at Knight-Swift Transportation and the 2023-2024 chairman of the the Truckload Carriers Association (TCA).