Influences on energy savings of heavy trucks using cooperative adaptive cruise control

Transport Canada’s ecoTECHNOLOGY for Vehicles program did a study on cooperative truck platooning systems and the effects of adaptive cruise control. This page summarizes our findings on how this technology saves fuel and energy.

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Executive summary

Transport Canada’s ecoTECHNOLOGY for Vehicles (eTV) program tests and evaluates emerging on-road technologies being employed within Canada’s transportation system. Cooperative Truck Platooning Systems (CTPS), or in this case, Cooperative Adaptive Cruise Control (CACC) are two such technologies currently being integrated into Canadian road vehicles. This report seeks to answer the question: what are the influences of CACC on energy savings of trucks (class 7-8) through the implementations of these technologies?

A CTPS study was conducted by Transport Canada’s eTV program, the National Research Council of Canada, the National Renewable Energy Laboratory, the University of California-Berkeley, FPInnovations and the Vovlo Group.

During this study, an integrated adaptive cruise control (ACC) and CACC was tested on three class VIII tractor trailers on a closed test track. The first truck was always in ACC mode, and the followers were in CACC mode using wireless vehicle-vehicle communication to augment their radar sensor data to enable safe and accurate vehicle following at short gaps. The fuel consumption for each truck in the CACC string was measured using the SAE J1321 procedure while travelling at 65 mph and loaded to a gross weight of 65,000 lb, demonstrating the effects of: inter-vehicle gaps (ranging from 3.0 s or 87 m to 0.14 s or 4 m, covering a much wider range than previously reported tests), cut-in and cut-out maneuvers by other vehicles, speed variations, the use of mismatched vehicles (standard trailers mixed with aerodynamic trailers with boat tails and side skirts), and the presence of a passenger vehicle ahead of the platoon.

The results showed that energy savings generally increased in a non-linear fashion as the gap was reduced. The middle truck saved the most fuel at gaps shorter than 12 m and the trailing truck saved the most at longer gaps, while lead truck saved the least at all gaps. The cut-in and cut-out maneuvers had only a marginal effect on fuel consumption even when repeated every two miles. The presence of passenger-vehicle traffic had a measurable impact. The fuel-consumption savings on the curves was less than on the straight sections.

  • SAE J1321


Trucks equipped with CACC proved to have a significant fuel saving when platooning.

  • The three-truck combined data demonstrated a wide range of fuel savings with the lead vehicle experiencing up to 10% at the closest separation distance of 4 m, with the middle vehicle experiencing a maximum fuel saving of 17% also at the shortest distance, and with the trailing vehicle experiencing a maximum fuel savings of 13% within the range of 10- 20 m
  • Significant fuel savings for the middle and trailing vehicles were measured at the largest separation distance of 87 m, measuring 6% and 8%, respectively
  • Total fuel savings for the three-vehicle CACC was measured at 13% at the shortest separation distance of 4 m, with 4.5% savings measured at 87 m
  • The lead and trailing vehicles of the two-truck CACC demonstrated the same trends in fuel savings with separation distance as the three-truck CACC, with a lower magnitude for the trailing vehicle
  • A cooperative three-truck scenario was shown to have a greater team fuel savings than that of a two-truck scenario (order of 2% higher, or more), for the range of common separation distances tested
  • Trends in data compare well with other fuel-economy data sets for similar vehicle types, speeds, and weights. Three-truck data also match trends observed from a wind-tunnel test
  • A reduction in fuel savings in excess of 1% was observed at small separation distance (12 m) when mismatched trailers were introduced into the CACC configurations, although the differences were generally within the confidence intervals of the data
    • No change in fuel savings was observed at 58 m separation distance
  • For equivalent cargo weights, a two-trailer long combination vehicle provided a greater fuel savings than the best performing two-truck CACC scenario (28% for LCV compared to 7% for CACC)
  • A reduction in fuel savings from CACC on the order of 1- 2% was measured when a periodic speed variation between 89 and 105 km/h was introduced every 100 seconds, with the CACC set to a 1.2 seconds time gap, as compared to constant speed driving at 105 km/h
  • Other road traffic can influence the fuel savings of cooperative heavy-vehicle automation systems
    • Some data showed beneficial effects of a string or platoon following an SUV, while other data showed no such benefit
    • Periodic cut-ins between the trucks showed no appreciable change in the fuel savings of the three-truck CACC with a separation time of 1.2 s (target distance of 25 m)
    • The variation in fuel-savings results for these “other traffic” scenarios suggest that energy savings are already being achieved while driving in general traffic, and that the cost benefits of cooperative truck automation systems may be influenced by the traffic scenarios in which such systems will be used
  • Two approaches to evaluating the difference in fuel savings between the straight and curved segments of the track revealed reduced fuel savings on the curved section of track than on the straight segments of track