Northville Downs, a harness racetrack in Detroit's western suburbs, has challenged a decision by the Office of Michigan Racing Commissioner to grant a Thoroughbred license to Magna Entertainment Corp. for its planned Michigan Downs.The appeal by Northville Downs was filed June 7 in Wayne County Circuit Court. MEC said it plans to build its $100-million track in Romulus near Detroit Metropolitan Airport, not far from defunct Detroit Race Course.Northville Downs claims a third racetrack in metropolitan Detroit would saturate the market. Northville Downs shares the market with Hazel Park, another harness track located north of the city. The two tracks make for a year-round live racing circuit, and both are open year-round as simulcast facilities that import Thoroughbred signals."We'll get into a money-losing situation and we'll have to close," Northville Downs lawyer Ed Draugelis told the Detroit News. "With the competition from casinos, we think the area can really only support two tracks."Michigan Downs wouldn't open until 2009 at the earliest. The Detroit metropolitan area has been without Thoroughbred racing since the fall of 1998 when DRC shut its doors. Hazel Park held Thoroughbred meets through the mid-1980s.Thoroughbred racing in Michigan is now held at Great Lakes Downs in the western part of the state. MEC operates the meet but had to transfer the track's license because state law says a company can't own more than one track.