If you hold down A+C and start on the pad plugged into slot 2 on the Saturn version of OutRun, it replaces the PRESS START message on the title screen with INSERT COIN! and even adds a "coin" button to the game.
This is a really neat feature that would make the game totally compatible with coin doors if you wired them up correctly. =]
This is also true of most of the SEGA AGES arcade conversions, including Space Harrier and After Burner II! The differences are minor so it's always an affoardable substitute for those of you who don't have the money to shell out on a $200 OutRun board. It really is nice, the amount of attention to detail they put into getting these games almost 100% arcade perfect.