Truck Platoons on the Move

August 1, 2018

Terry Costlow

Research into truck platoons is running hot as companies investigate benefits such as fuel savings, safety, diminished congestion and reduced driver fatigue. Before these gains can be realized, a number of driving and technical issues still need to be resolved, and regulators need to alter several rules.

Truck manufacturers and customers like FedEx and UPS are ramping up trials to see how closely vehicles can convoy. The tests will help them determine whether fuel savings gained by drafting are cost effective and whether vehicle-to-vehicle (V2V) communications can improve safety.

Interest in platooning is high. Most trucking OEMs have run studies and fleet-owner interest comes from the top — FedEx CEO John Smith recently attended Volvo Trucks’ demonstration of a three-truck convoy in North Carolina.

Platooning trucks can cut fuel consumption by up to 10%. Congestion will decline with shorter following distances and driver fatigue can be reduced and safety enhanced because braking is automated.

The Dept. of Transportation’s Volpe Center determined that automated vehicle response technologies can yield “very little crash risk even at 0.5-second following distances.” Normal following time is about 2 seconds, according to Volpe. When trucks can communicate, the shared input can dramatically improve safety.

“If standards are in place, vehicles can report not only vehicle position, speed and traffic conditions, but environmental information such as visibility, slick roads, etc. that can be useful for following vehicles,” said Dan Williams, Director, ADAS and Autonomy, Commercial Vehicle Technologies, at ZF. “In an urban environment, a leading vehicle could share its object-detection information with following vehicles, so that the following vehicle can know where pedestrians are even if they are blocked in the following vehicle’s field of view.”

While trucking companies stress that platooning won’t lead to driverless vehicles, it is serving as a proving ground for V2V. It is often touted as an important technology because it can provide input that can’t be collected using on-board sensors. For example, V2V can relay to platooning vehicles when a car in front of a large truck is braking.

Driving issues

Even ardent proponents of platooning say many concerns must be addressed before convoys are commercially viable. Determining the following distance between trucks highlights both technical and regulatory challenges. A few states have okayed short following distances for platoons, but most still have restrictions. On the technical side, it’s difficult to ensure that vehicles stop in synch regardless of load conditions.

“The first step is to identify the primary determinants of brake performance such as tire and brake conditions, vehicle mass, etc.,” said Derek Rotz, Director of Advanced Engineering, Daimler Trucks North America. “Next, a sensitivity analysis is needed to quantify their impact on stopping distance. From that, a safe following distance can be derived. This work is ongoing.”

Studies must determine where and when platoons make sense, as well as whether to communicate with infrastructure systems. Many researchers now focus solely on V2V, ignoring potential communications with infrastructure elements like roadside stations and the cloud. However, others contend that vehicle-to-infrastructure communications bring significant benefits.

“We need to communicate with the infrastructure for things like weather, traffic flow, road conditions and other factors that impact separation distance,” said Darren Gosbee, Vice President, Powertrain and Advanced Engineering, at Navistar. “We’re also looking at things like optimal locations for platooning. Mountains and high plains make a lot of sense; congested areas are not where you want to platoon.”

Many technical issues are fairly-well proven. V2V links that use 5.9-GHz dedicated short-range communications (DSRC) have been tested extensively, as have the adaptive cruise control devices that provide redundancy for safety. However, not all the system certification processes have been updated to address platooning.

“Without Federal Motor Vehicle Safety Standards (FMVSS) standards to certify to, there are hurdles to rolling V2V out,” said Keith Brandis, Vice President for Product Planning at Volvo Trucks North America. “We’re operating in the blind for how to get field approval.”

A lack of regulatory action has also helped give rise to a challenger for DSRC. Most automakers plan to put cellular modems in vehicles, so some companies started examining cellular as an alternative to DSRC. If support for technologies developed by the 5G Automotive Association gets a foothold in automotive, it could change the volumes of DSRC modems.

Truck companies have largely remained focused on DSRC, which has been extensively tested. Platooning technologists also like the low latency of DSRC. While communication between cars and trucks brings benefits, developers are currently more concerned with communications over the truck’s CAN bus than with passenger cars.

“Trucks use a version of DSRC that’s designed to work with J1939,” Brandis said. “We have demonstrated communications between Volvo cars and trucks, but that’s not a major issue right now.”

In the event of failure

Functional safety, a mainstay of vehicle design for years, also changes for platoons. When a component or system fails, many strategies address safety by stopping the vehicle. In platoons, returning control to drivers can be an effective alternative.

“Functional safety requirements increase due to the nature of platooning,” Rotz said. “A platoon operates at following distances too close for an average human driver to respond; therefore, in the event of a component failure, the system shall bring both vehicles to a safe state — in other words, to a larger following [distance] suitable for the driver. This requirement drives several aspects of component and system design.”

Connectivity brings another safety concern — cybersecurity. Vehicles need to know that they are indeed communicating with trucks in close proximity, not a hacker or a truck above them on an overpass. Vehicle systems like brakes also need to know signals are coming from authorized modules.

“One aspect is to develop according to current industry guidelines and best practices for addressing cybersecurity, such as SAE J3061,” Rotz said. “Another aspect is deployment of certificates and certificate authorities to certify the authenticity and integrity of the communication channel. These are commonplace for V2V deployments in industry today. Furthermore, it is beneficial to use external services that provide threat analysis and perform several forms of intrusion or penetration tests on the designed system. These are but a few tools at our disposal to ensure safe communications.”

Business concerns also change when convoy vehicles aren’t all in the same fleet. Lead vehicles will create drafts that improve mileage for trailing vehicles. It may be hard to find “leaders” if they don’t get compensation.

“Monetization will be a challenge,” Gosbee said. “The truck drafting behind the lead vehicle may not be in the same fleet. There’s potential that a trucker could be giving a benefit to a competitor. Communications to the cloud will change; now you’re talking about handling money.”

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