This is just an idea that I've been toying with(pun intended) for a while. After visiting http://www.dcraction.com, I realized my idea really isn't "new", but I think it has the potential to add some depth to diecast car racing.
"Open Track"...imagine 6 to 8 cars racing simultaneously on a <<wider>> version of Sizzlers Fat Track laid out in a very large, symmetrical gravity coarse. Like DCR, individual lane track could be used for the starting gate and to allow the cars to acquire some speed before hitting the open track. After that, the cars would mix it up with no barriers between them. In the interest of making the the coarse even, a spiralling figure-8 design could be used with a long starting straight away, 1 200deg banked RH curve, another long strait section, 1 200deg banked LH curve, and then a long run-off straight away to a finish line. The track itself would be 10"-12" wide with 'stability grooves' similar to those used on Fat Track to aid vehicle tracking and help reduce spin-outs. (The grooves could be ~.5mm taller on the high-banked curves to further aid with stability.) As you can imagine, this gravity coarse would be BIG with 3 straight away sections, each measuring 50-70ft leading into & out of the curves. There would be no bumps, jumps, uphills, or flat sections...just a constant, gradual downhill run that would allow the cars to build momentum slowly and finish with blistering speed. I figured that a constant, low downward angle in the coarse might give spun-out cars a chance to regain momentum and finish the race.
Now, if you really think about it, using existing methods of choosing cars to race on such a coarse go right out the window. Outright 'weight' will be most likely over-ridden by more favorable 'center of gravity' and 'weight distribution' characteristics. Also, 'tracking'(ie: a car's ability to go strait) probably becomes "king" on the open coarse. Even narrow-axle cars might stand a chance on the grooved track. Car design also may be a major factor. Open-wheeled/exposed-wheel cars may be at a disadvantage on a crowded, wide track. As they say, "rubbin' is racin'" and other cars rubbin' against those exposed rolling wheels could be a momentum killer.
Well, that's my idea in a nutshell. I have many other unmentioned particulars that would go into building such a coarse...if I ever get that far. The specific design is still in my head and I haven't actively begun evaluating materials for building it yet. However, I do value the experienced opinions here and would welcome any insight or criticism...so, fire away!