SmartFlap: 9% lower fuel costs for trucks from enhanced drag reduction

Reference number 7584

Sectors: Industrials

Industries: Aerospace, Defence


The design of many road vehicles is aerodynamically inefficient, in particular large road vehicles have a blunt rear end which generates a wake that can lead to dissipation of up to 25% of the total energy produced by the engine.

Improvement of the aerodynamic efficiency is key for environmental, economic and practical reasons. In 2017, road
transportation produced 7bn tonnes of CO2 by using 3tn litres of fuel at a cost of $3-6tn. Aerodynamic efficiency is also important in increasing the range of electric vehicles.

SmartFlap is a crucial technology which significantly improves the aerodynamic efficiency yet requires only a small geometric modification, equivalent to the spoilers already present on many vehicles.


Building on over 5 years of intensive research into the behaviour of turbulent wakes on the bluff body shape of trucks, engineers at Imperial College London have optimised a system which accounts for the effects of yaw angle flow caused by either cross winds or vehicle manoeuvring, e.g. cornering and overtaking. Resulting from a deep understanding of the flow fields created around the truck in these conditions, the team has developed an adaptive flap system that modifies in real-time the flow around the truck. Further information can be found in theĀ datasheet for this technology.


  • Fuel savings for a standard truck drive cycle of 9%
  • Low cost system to ensure pay-back in investment
  • Unobstructive, robust flaps which allow normal loading and unloading in docking bays
  • Suitable for retro-fitting and new equipment
  • Can be compliant with design and performance regulatory requirements
  • Experimentally tested and clear understanding of the net energy savings


  • Truck trailers, rear and side loading
  • Automotive rear spoilers
  • Coaching industry

Intellectual property information

Drag reduction method: International Publication number WO2017/072530. It is also published as GB2544044 and EP3368397.


Professor Jonathan Morrison

Professor of Experimental Fluid Mechanics
Faculty of Engineering, Department of Aeronautics

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Contact us about this technology


Dr Laura Cabo-Fernandez

Industry Partnerships and Commercialisation Executive, Engineering

Dr Laura Cabo-Fernandez is Industry Partnerships and Commercialisation Officer for the Faculty of Engineering at Imperial College London.

Contact Laura

+44 (0)75 9025 0597

[email protected]

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SmartFlap: 9% lower fuel costs for trucks from enhanced drag reduction

SmartFlap: 9% lower fuel costs for trucks from enhanced drag reduction

The SmartFlap technology provides possibly the best yet solution to reducing drag caused by the turbulent wake at the back of a truck. It uses actively controlled flaps of similar size those of currently available systems, which operate at a slow speed over a narrow range of movement, delivering fuel savings of up to 9%. The demonstrated drag reduction and potentially low cost of the system make it a cost effective investment for truck operators. Also, the size of the flaps and ease of installation ensure that they will be robust and unobstrusive for loading operations as well as on the road. Find out more

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