Trailer Talk

‘Platooning’ Tractor-Trailers Raise Questions at TMC Meeting

Productivity, safety and fuel economy could be increased by running trucks together. But is it practical?

October 1, 2015

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Image: Volvo Trucks
Image: Volvo Trucks

Can cargo-carrying trailers be pulled to their destinations with less involvement by drivers? If so, it could help solve the worsening driver shortage. That and overall productivity and efficiency are the reasons for development of electronics that enable “platooning” – two or more trucks running together, one leading the other(s), to gain operational economies.

Autonomous vehicles — something separate but related — have been in the news since Freightliner and Peterbilt showed off their versions a couple of months ago. These are not self-driving vehicles, both builders have emphasized. Google is developing a self-driving car, and has given rides to general media reporters. Positive publicity on that and other self-drivers might pave the way for automatically operated commercial trucks because motorists are more likely to trust the vehicles, it seems to me.

There are intriguing implications here for commercial trucking, and technically much of it is entirely doable now or in the near future. The American Trucking Associations’ Technology & Maintenance Council is on to both things, and just okayed the adoption of a White Paper: Automated Driving and Platooning Issues and Opportunities. It discusses where development is and what its prospects are.

One of the paper’s writers, consultant Richard Bishop, summarized its contents in a session at the recent TMC meeting near Orlando. He spent most of the time on platooning, which for now envisions two tractor-trailers operating together, with wireless signals from the first tractor telling the second tractor to speed up, slow down, brake, etc. Peloton Technology, which is backed by Volvo and Lockheed Martin, has demonstrated a pair of rigs with such controls; for now the second rig’s driver must steer, but otherwise he leaves his feet off the pedals.

Following distance is 30 to 50 feet, and those in the audience wondered if staring at and trying to follow the lead trailer wouldn’t be tedious for the second driver. Test drivers haven’t complained about that, said Peloton representatives. The distance is longer than it might seem; also, the second driver’s view is more than the first trailer’s rear, because he has an in-cab screen with a telecast of what the first driver sees on the road ahead. There are state laws against watching TV while driving, some in audience noted. So is that legal?

The lead tractor controls the second tractor’s accelerator and brakes. That means the two rigs would have to be pretty well matched in power so they stay together, even when climbing hills. And the second rig must be able to stop quicker to avoid rear-ending the first one, especially in panic stops. Two rigs from the same carrier could be set up for compatibility, but cargo weights vary and brakes go out of adjustment. How exactly would the lead and following rigs be picked?

Electronic controls know what’s happening between the two rigs, so can adjust the distance or disconnect if a car darts in between the two. The second rig’s driver could also do that. But interloping autos are dangerous anyway, so platooning would not be advisable on urban freeways, at least not when there’s a lot of other traffic. That might limit the capability to long rural runs, and there plenty of those in this country. Meanwhile, should some special markings be designed to tell motorists that two or more trucks are platooning (maybe like “convoy ahead” signs used by the military)?  

The second rig’s driver isn’t doing as much as the leading driver, so what’s the second guy’s log-book duty status? Right now he’d be On Duty, Driving, but maybe an additional classification could be created, especially if the second tractor is also automatically steered.

In that case, could the second driver be given some paperwork to do instead of having him just sit there? Could he be allowed to make phone calls, do some texting, even watch a movie or take a nap? Probably not, because such distractions would delay his response in an emergency, when he might quickly have to take over the controls in his tractior.

Wait – if there’s a driver in the second rig, where are the economies in platooning? Safer and more economical operation, Bishop explained. The second driver needn’t concentrate as much, especially if his tractor steers itself, so he’d be less fatigued. And tests have shown that aerodynamics are improved because the two rigs are “drafting,” an old car- and bicycle-racing trick where two or more vehicles purposely run closely together to give each other a boost.

In drafting, the lead vehicle breaks through the air so the second one doesn’t have to. The second vehicle therefore doesn’t need as much power, and with a big rig, its fuel economy improves by up to 10%, the white paper says (other tests put it at up to 15%). The first rig also gains because the turbulence behind its trailer is smoothed out by the second rig, and the lead rig gets as much as 5% better fuel economy. Is that enough dollar savings to justify the equipment and administrative costs in setting up and managing a platooning operation?

What if the technology got so reliable, safe and trusted that the second rig could be driverless? And if a third and fourth rig could be added to the lineup? Tests like this have been done in Europe, and now we’re talkin’ productivity. But is that politically feasible on public highways? If one of the trucks hit something or somebody, where is the liability? And where would such a super rig be staged and separated?

Know what? That’s been done for years with mechanically linked long combination vehicles and road trains here and in Australia. Those are technologically much simpler than electronic platooning, though not politically popular in many areas. Most questions about platooning could be worked out, though it would take time. Still, because of the practical problems, some in the audience at the TMC session were not enthusiastic about the idea.

(Not so incidentally, truck-rail intermodal operations accomplish the same goals, though without near as much flexibility and sometimes with poor reliability. But that solution exists, it gets rigs off congested highways, and it lessens the driver shortage among long-haul truckers.)

Back to autonomous, automatically operated trucks: The TMC white paper says that there are more uses for this than simply going down a highway. One example is “moving trucks in a queue” where drivers can relax while electronic controls inch their vehicles forward at a port gate or job site. Staying in line in stop-and-go traffic with little driver tedium is another practical use. I’ll get into this in a future blog.

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Author Bio

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Tom Berg

Senior Contributing Editor

Journalist since 1965, truck writer and editor since 1978. CDL-qualified; conducts road tests on new heavy-, medium- and light-duty tractors and trucks. Specializes in vocational and hybrid vehicles.

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