Archrivals Alain Prost and Ayr-ton Senna crashed at the Japanese Grand Prix in Suzuka for the second time in two years, allowing Senna to walk away yesterday with the 1990 world Formula One championship.

Ironically, the wreck last season gave Prost his third Formula One title at the expense of Senna, the 1988 driving champion. Winning yesterday was Nelson Piquet in a Benetton Ford in 1:34:36.824 (122 mph), but Senna and Prost's season points were beyond his reach.

Last year Senna and Prost crashed in one of the final laps. This year it happened seconds after they started, at the front of the pack with Senna on the pole. Prost moved quickly in front; Senna tried to regain the lead by passing from inside. Prost maneuvered to the right for the first turn; his Ferrari hit Senna's McLaren-Honda, sending parts flying. Both drivers spun out into the dirt, unhurt.

Indy Cars: Danny Sullivan led every lap of the 300 kilometers at Laguna Seca Raceway, Monterey, Calif. Al Unser Jr., starting fourth in the 27-car field, took second by the end of the second lap and kept it, ending 29.799 seconds behind.

NASCAR: Alan Kulwicki, taking advantage of a last-minute caution flag to end a two-year winless streak, outlasted Bill Elliott in the AC-Delco 500 in Rockingham, N.C.