Skip to main content

New car roof means reduced fuel consumption

Published Feb 11, 2011

A researcher at KTH has managed to reduce the weight of the car roof by 80 percent without making the roof significantly more expensive or producing inferior properties. If anything, the opposite is true, the new roof provides greater comfort and it is much easier to hear your passengers when you talk to one another. If the techniques used for the design of the roof of the car are also applied to the entire vehicle, it can reduce fuel consumption substantially.

"The objective of this research project has been to develop design methods for the construction of future cars with improved environmental and economic performance," says Christopher Cameron, researcher and doctoral student behind the new car roof.

He clarifies the project by saying that it is really about an entire roof system . When you start talking about the roof of a car, people may think that it is only the sheet metal that is being replaced, and what is so special about that? In addition, the design method is applied to all parts of the body not just the car roof.

Christopher Cameron does not have any exact figures yet as to what the new roof will generate in terms of reduced fuel consumption - which obviously varies from model to model - but says that it involves a significant amount. For example, a 10 percent decrease in a car's weight, leads to a 7 percent decrease in fuel consumption.

At the same time it is important to remember that the roof is about 10 percent of the car's body weight and about 2 percent of the car's total weight. On a single car, these figures may seem modest, but in terms of all of the world's cars and the amount of time they spend on the roads, it amounts to very large savings in fuel consumption and it therefore has a positive impact on both fuel economy and the environment.

"With the solution we have for the new roof, the dead space will disappear in the coupé as beams and other components become integrated. It means that you can reduce the thickness of the roof. Then without there being any effect on the comfort, you can lower the roof height of the car which provides a sportier profile, reducing drag and fuel consumption," says Christopher Cameron.

He reiterates that the research project is only one small study which involves a relatively small area of the car. If more parts of the car body are replaced by a so-called sandwich structure, the weight can be reduced even more.

"The effect is even greater when you extend the design methodology to the remaining parts of the car and reduce weight even further. If we reduce the weight of the structure we will not need such a large engine, the brakes will no longer have to brake such a heavy vehicle which will mean that even the brakes can be made smaller, etc. This may mean that you can further reduce the weight of the structure. There will be a positive weight minimization spiral," says Christopher Cameron.

In addition to reduced fuel consumption, the roof system is constructed according to the same specifications as existing roof solutions today, so it can be just as safe as before.

"Speech intelligibility - i.e. how easy it is to talk and be understood between the front and rear seats - seems to have improved with the new roof. This may sound unfortunate, but it is a huge thing when you have reduced the size and bulk of the roof so radically. Reduced mass is something that is usually associated with increased noise and vibration problems in industry," says Mr Cameron.

The automotive sector is also in favour of Christopher Cameron's research.

"This research project is a collaboration with SAAB, and they think my work is very promising," says Cameron.

For more information, contact Christopher Cameron på 070 - 283 62 52 or

Peter Larsson