The message is pretty clear: come up with lighter steel alloys or lose out big time to aluminium, plastics or composites.

It’s a message that Arcelor Mittal has taken very seriously as the company has come up with a 29lb car door having tested 1,500 different designs over a three-year period at its global R&D facility in the USA.

The new door weighs 27% less than standard car doors, which is good news for car manufacturers who must double fuel efficiency to an average of 54.5 miles per gallon by 2025.