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Safety and autonomous trucking drive new standards for tractor-trailer hookups

Smaller gaps help fuel economy but raise difficulty of drop-and-hook operations

Connecting tractors and trailers is a common source of injury for truckers. Photo: Jim Allen/FreightWaves

As the gaps between tractors and trailers shrink through aerodynamic design, making connections safer is only one concern for standards-writing engineers who must account for autonomous trucking in the near future.

The Society of Automotive Engineers (SAE) is developing new standards for hookups that tackle two contentious issues: tractor-trailer interconnection that let the two units communicate, and the best way to electronically couple them to reduce driver injury.

“There is little consensus on a common connector system for the future,” said Dave Engelbert, chair of the SAE Truck and Bus Brake and Tractor-Trailer Interconnect group. “It is very political.”

For example, a global solution is needed to harmonize European trailers that connect with North American tractors sold in Australia, said Matthew Fry, an engineering manager Knorr-Bremse Group AG, the German industrial holding company and parent of Bendix Commercial Vehicle Systems.


“The amount of data is exploding and we need a system that can report back and forth,” said Wally Stegall, vice chairman of the future truck group of the Technology and Maintenance Council of the American Trucking Associations (ATA). Tire pressure monitoring systems, door sensors, solar panels, and wireless temperature sensors are just a few of the data sources.

Engelbert, Fry and Stegall spoke at the recent SAE COMVEC Technology Connection meeting in Indianapolis.

“Anytime you try to create standards, it’s hard to get everybody to agree,” said Mike Roeth, executive director of the North American Council for Freight Efficiency (NACFE). “But that’s not a reason not to do it.”

Compatibility counts


An SAE task force reviewing voltage systems used by North American heavy-duty truck manufacturers recommended in October 2018 that 12-volt direct current should be used with the interface governed by existing SAE standards. The task force said 24- or 48-volt DC connectors should be options based on demand. 

With many truck makers pledging to offer high-voltage battery-electric trucks for sale early in the next decade, a new standard probably will be needed.

Kenworth Truck Co., which is working with Toyota Motor Corp. on an experimental fleet of 10 hydrogen-powered fuel cell electric heavy-duty trucks, is using 48-volt power systems to run cooling fans and pumps, said Brian Lindgren, Kenworth director of research and development.

Volvo Trucks North America has twin 12-volt battery systems on its retrofitted battery-electric VNR day cab model that it will sell in selected states beginning in 2021.

“With the continual buying and selling of equipment, fleet mergers and consolidations, and for the long service life expected, compatible electrical connections is a critical factor” in making trailers worth their investment, according to a position paper by the ATA’s maintenance council.

Electronic hookups

Truckers often are injured in slips, trips and falls when hooking or unhooking cables between tractor and trailer. As farings and other gap-closing technology become common to improve fuel efficiency, access to the space between the tractor and trailer is getting more difficult.

New fifth-wheel designs and trailer electric brakes could eliminate cable hookups because the tractor would allow electronic coupling, according to Chris Lee, vice president of engineering at Great Dane.


Great Dane and Jost International, a maker of fifth wheels and king pins that secure them, conducted a test with an autonomous tractor for Walmart in 2018. Lee said the nation’s largest traditional retailer wants its yards to operate with fully autonomous trucks.

Drop and hook

More immediately, the makers of gap-closing equipment need to consider the rise of drop-and-hook operations as dry van freight moves shorter distances and is pushed into hub-and-spoke distribution, Roeth said.

“The gap closure devices that are emerging mostly deploy at 50 mph and stow below that,” he said. “People creating those systems that close the gap need to design for drop and hook.”

8 Comments

  1. Ryan

    This has the biggest crock I’ve ever had to read! All this new technology is only to bring low and middle class Americans to there knees! They’re replacing employees with robots at Mc Donald’s some walmarts have robots that shop check it out then meet you at curb side etc etc… America as we once knew it “the hard working folks” are being pushed around and out at a rapid paste! They’ve crippled the farmers now their going to do everything in there power to cripple every other aspect of small businesses! Everyone needs to come together nation wide and put a stop to this!

  2. steven campbell

    Slips, trips & falls while hookin up….i’ve heard it all. Guess the SAE is working with trucks and trailers that I have never seen.

  3. John

    If a human is required t do it, you can bet the engineets are determined to find a way to get rid of you. I want to blame the engineers but they’re just educated puppets of corporate America and as soon as they come up with AI that can do the job of Engineers, the Engineers are going to be unemployed too.

  4. Truckdriver

    I think they need to focus on the overall regulation of the trucking industry by people who cannot grasp the shortage of “middle class” truck drivers and why it exists.

  5. Mike Balutis

    The industry always trying to improve performance of the vehicles made and manufactured. Great ideas but this time not important. As a driver of many trucks from small cargo vans up to tractor trailers for nearly 50 years focus is desperately needed in the medium-sized truck market. The package van or step series. The trucks on the road today are garbage. Quality is non existent. From performance to electrical. And the cost doesn’t match the so called improvements.

  6. RD

    80,000 lbs rolling at 60mph is death on wheels if there is no driver behind the steering wheel because the stopping distance is way too long.

    The only way that I’ll work is if the truck and trailer can “see” two and three trucks ahead.

  7. Samuel Euresti III

    As a professional driver, coupling and uncoupling has never once proven to be an obstacle. I didn’t even realize that it was an issue, until I read this article. A driver would have to score pretty low on the IQ scale in order to hurt him/herself during a “drop & hook.” Most of the real dangers show themselves either while driving or when trying to find a safe haven with little to no time left on your clock.

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Alan Adler

Alan Adler is an award-winning journalist who worked for The Associated Press and the Detroit Free Press. He also spent two decades in domestic and international media relations and executive communications with General Motors.