The bridge, to ease congestion at the two nations' busiest border crossing, would be built next to or connected to the Ambassador Bridge. Several competing plans for additional border crossings have been put forward in recent years. The need for an additional crossing has been accentuated in recent times because of heightened security in the post-Sept. 11 era, although some changes at the border have been made to reduce some of the backups.

Owned by Grosse Pointe trucking mogul Matty Moroun, the bridge company is under no obligation to build another span or make long-range plans public. Bridge officials expect project studies to take 18 months.

The Detroit-Windsor Tunnel and the Ambassador Bridge handle more traffic than any other spot on the long US-Canada border. Much of the traffic, particularly on the bridge, is heavy commercial trucks that carry parts and supplies to and from auto plants in Ontario and the Upper Midwest. The existing tunnel is too small to handle large trucks.