Apartment towers could soar above the Eastern Freeway one day, with easy access to Melbourne's first high-capacity "busway" below.

French-based transport company Transdev wants to build and operate Melbourne's first rapid transit bus system, between Doncaster and the CBD, and has proposed selling property developers the "air rights" to build above the freeway to help pay for it.

The Gate Tower building in Osaka, Japan.

Two sites – the freeway interchange at Chandler Highway in Kew, and the park and ride facility in Doncaster – have been identified by Transdev as opportunities for future "transit-oriented development" if the busway goes ahead.

This would involve building directly above 10 lanes of traffic on the Eastern Freeway in Kew.