Meritor Automotive, which pioneered the one-piece roof module in Europe on the DaimlerChrysler MCC Smart car, is pushing the concept globally and now has development agreements with four automakers.

The Troy, MI, supplier isn't identifying the customers except to say they are considering the modules for cars and light trucks in various markets, likely by 2004.

Currently, roofs are stamped, formed and welded to the body early in the process. Meritor proposes that bodies be built only with roof rails and support pillars. The rest of the roof would come later, after large systems such as seats and the instrument panel, are lowered through the roof, rather than through tight door openings. The roof module would be mated with a finished headliner.

Terrence O'Rourke, president of Meritor Light Vehicle Systems, says new plants likely will be necessary, perhaps near OEM customer plants. He says the global market for roof modules could reach $15 billion a year.

The company says the module saves cost (for OEM and supplier) by 30% and reduces weight by 40%, improving fuel efficiency and handling because of a lower center of gravity. The weight reduction comes from the use of thinner steel or aluminum, mated to a polyurethane foam layer for structural rigidity.