We’re all sensitive to fluctuating fuel prices, but the rise and fall of crude has an acute effect on trucking companies. The average commercial truck consumes about 20,500 gallons of diesel per year and gets 5 to 7 mpg. Fuel accounts for about 35 percent of a truck’s operational cost, the single largest expense.

So when the Environmental Protection Agency today proposed fuel economy standards for trucks built between 2021 and 2027, there wasn’t widespread opposition: the EPA wants to curb emissions, and fleets want to save money. The EPA, which issued the proposal in conjunction with the National Highway Traffic Safety Administration, is only proposing emissions reduction targets, such as 24 percent for the largest commercial trucks. How truck makers achieve that goal is up to them.

More efficient engines, smoother transmissions, and low-resistance tires are methods that will certainly be used. But Kenworth, which is based in Kirkland and has a plant in Renton, is targeting a more fickle, non-mechanized variable with its latest efficiency technologies: the driver.

“Kenworth regularly evaluates new technologies that can provide enhanced driver performance, fuel efficiency, and fleet productivity. Kenworth especially focuses on technologies that can benefit customers today,” Kurt Swihart, Kenworth’s marketing director, said in an email.

The most significant of these innovations is Kenworth’s Driver Performance Assistant, an in-dash performance monitor that evaluates a driver’s speed moderation, coasting, and ease of braking. The system factors in these fuel-economy factors and then spits out a score, giving a driver a more concrete idea of how efficiently he or she is driving.

There’s good reason to begin with the driver when trying to improve fuel efficiency. Trucks can be tuned for efficiency, but “drivers are another variable,” Kenworth Chief Engineer Kevin Baney said in a statement. “Everyone drives differently, and the gap between a fleet’s highest performer in fuel economy can be vastly different from the lowest performer.” Even the most efficient truck won’t counter a diesel-burning aggressive driver.

While the Driver Performance Assistant gives the driver real-time feedback, other systems the company is employing aim to handle some of the more mundane on-the-road chores. Kenworth’s most fuel efficient trucks automatically adjust cruise-control speeds based on surrounding traffic and topography, thus minimizing sudden braking and inefficient driving in rolling terrain.

All these systems help a human driver, but they’re all elements that would be necessary for what many consider would be the most fuel-efficient vehicle of all: a driverless truck. Fleets have reason to abandon drivers — humans swerve, sleep, and have to stop at a truck stop to relieve themselves and eat. Computers are more predictable and, you know, don’t have to be fed. Costs would go down, efficiency would go up, and it would be easier to meet the potential EPA standards.

There’s already movement afoot in the self-driving truck world. In May, Daimler caught the attention of the transportation industry and futurists alike when it unveiled the Freightliner Inspiration, the world’s first licensed autonomous truck.

The truck’s not fully autonomous — its self-drive mode only kicks in on the highway, where it will stay in the same lane and not crash into other vehicles — but it’s a step in what’s looking like an inevitable direction in the industry.

Kenworth and its parent company Paccar won’t discuss self-driving rigs, a spokesperson said, but efficiency implementations like the ones Kenworth has rolled out are precursors to autonomous driving.

Self-driving vehicles need a few key components: Sensors telling them where they are and where to go, sensors monitoring surrounding vehicles, and systems to interpret that data and convert it into throttle, braking, and steering commands. Kenworth tucks today have the first two ingredients covered, and its Driver Performance Assistant is a rudimentary form of the third.

If the EPA standards are implemented, Kenworth will make mechanical fixes to boost truck efficiency. But when it comes to eliminating, or at least heavily assisting, drivers, the Kirkland company at least has a foundation for that step toward efficiency.