Sunday's opening of the Detroit Motor Show saw the unveiling of forty new or improved vehicles from America's Big Three auto manufacturers, General Motors, Ford Motor Company and DaimlerChrysler.

The flurry of new and enhanced models is viewed as a robust counter-offensive on the growing erosion of US manufacturers' market share by Japanese and European competitors. But GM is going that extra mile to zap its overseas -- and indigenous -- rivals.

The Detroit leviathan plans to give away one thousand new vehicles in a two-month-long promotion, starting today (Tuesday). Touted as "the largest vehicle giveaway in history", the promo involves the whole of its 54-vehicle product range.

To win a car, consumers must visit their local GM dealer and push a "hot button" linked to a call centre via GM's OnStar on-board vehicle communications system. Five and a half million people are expected to participate in the $50m (€39.44m; £27.80m) promo, half the cost of which is the value of the vehicles.

Says GM's director of retail planning, Steve Hill: "Given that the chances of winning are about one in 5,500 - which is a lot better than many lottery odds of about one in 14m - we know this promotion will have a great deal of consumer appeal."

But whether it also sells autos remains to be seen.

Data sourced from: Financial Times; additional content by WARC staff