Rainbow Road to Oz was a proposed, but unfinished film. It was supposed to be a live-action film made by Walt Disney Studios about characters in the Land of Oz and inspired by L. Frank Baum's Oz books.
Why It Was Cancelled
It is theorized that the reason was because Disney failed to develop a satisfactory script and the popularity of the MGM adaptation of The Wizard of Oz represented potential insurmountable comparisons.
Disney aired previews of the film on television in 1957.
It was replaced with a new adaptation of Babes in Toyland. However, Disney did eventually create two adaptations: Return to Oz in 1985, and Oz the Great and Powerful in 2013, the latter of which currently has a sequel in development.