Black smoke billowing from a big rig's chrome exhaust stacks is a staple image of classic country truck-driving songs.
"I'm gonna sign my name in this diesel smoke, and let the ones that come behind me choke," Del Reeves sang in his 1968 hit, "Looking at the World Through a Windshield."
Today's high-tech diesel trucks, however, don't blow smoke - or have much in common under the hood with the trucks of yesterday that inspired the musical genre.
For example, being a "Gear Bustin' Sort of a Fella," as songwriter Bobby Braddock put it in 1967, is on its way out.
Automatic transmissions - which are easier to drive, reduce fatigue and therefore make driving safer - are becoming the norm, said Dan Porterfield, vice president of maintenance at Covenant Transport.
"It's still a manual transmission," Porterfield explains as he shows off the features of the 2018 Freightliner New Cascadia, one of the makes and models of diesel truck used by Covenant. "It's just shifted by a computer. It's a 12-speed manual that shifts itself."
That hybrid setup offers the ease of an automatic, yet retains the reliability of a manual transmission, Porterfield said.
Reliability's important, since Covenant tries to keep its trucks on the road for 500,000 miles before replacing them. That may sound like a lot, but it isn't these days.
"A million miles, a million and a half, anymore, is no big deal for a truck," Porterfield says.
A growing number of people have never driven a personal vehicle equipped with a manual transmission.
"All they've known is automatic transmission," says Rob Hatchett, vice president of recruitment at Covenant. "For many of those people, requiring them to learn to drive a manual transmission has been a barrier to entering our industry. The growth of automatic transmissions [in trucks] over the past couple years has come at a perfect time as we are facing a looming driver shortage."
Some of the Covenant's old-school drivers have threatened to quit rather than switch to an automatic transmission, Porterfield said. But once those drivers use an automatic for while, he said, they tend to prefer it.
Cameras, GPS and radar
Other technologies in Covenant's trucks include Bendix brand cameras that record incidents of sudden braking and send footage to Covenant's headquarters. An employee there can review the incident and praise the driver if they've skillfully evaded a car that swerved in front of their truck - or use it as an opportunity for training.
Covenant's trucks are equipped with global positioning satellite technology that shows a truck's exact position and gets it to automatically speed up to climb a grade and slow down to descend.
Covenant's trucks also have lane-sensing technology that alerts drivers when they're drifting.
Radar in today's trucks allows for adaptive cruise control that slows a truck down when there's a slowpoke ahead.
The 2018 Freightliner New Cascadia has so many computers and electronic controllers that there's a compartment for all that inside the cab called the "E-bay."
Trucks to 'platoon' like geese?
Covenant Transport hired Porterfield in 1995 to help improve the fleet's fuel efficiency, which then was about 6.3 to 6.4 miles per gallon of diesel.
"Our next goal for us at Covenant Transportation is 10 [mpg]," he says, which he thinks is attainable. "With current technology? Not really. But do we think we'll get there? Yeah."
Porterfield appreciates anything that can help improve mileage, including aerodynamic mud flaps with horizontal slots that reduce wind resistance and improve a truck's fuel efficiency by one quarter of 1 percent. They'll be on all of Covenant's fleet eventually, he said.
A novel proposal to improve trucks' fuel-efficiency that manufacturers have eyed is using the modern-day truck's various sensing technologies to allow big rigs to "platoon" closely together and draft off each other like Canada geese flying in V-shaped formation.
As technology takes the fore, icons of trucking's old days have begun to fade away. Even CB radio is losing popularity, Porterfield said. Drivers don't bring their own CBs as much as they used to.
"It's getting where it's less common. Everybody carries a [smartphone] now," he says.
But not everything about trucking has changed. Kids in the back seat can still motion for a passing truck driver to blast the horn.
The Freightliner New Cascadia still has the traditional loop that hangs from the ceiling to honk the truck's super-loud highway air horns.