Will Porsche 918 Coupe hit the road?

* Spyder order books open today * but will a coupe road car be built? * Hard-top could be confined to the track...

Order books for the Porsche 918 Spyder hybrid supercar opened today, but the prospects for a road-going coupe version don't look good.

Although a 918 RSR racing coupe was unveiled at the Detroit motor show earlier this year, it looks as if a hardtop shown here in our computer-generated image could be confined to the track.

No mention of a possible coupe version has been made by the company, while Porsche's most-recent supercar, the Carrera GT, was available only as a convertible.