A skyrail up to nine metres high will be built over Toorak Road in Kooyong, next to the Monash Freeway, to replace one of Melbourne's most congested rail crossings.

The elevated railway line will be 550 metres long, stretching between Kooyong and Tooronga stations in Melbourne's east.

The state government plans to build a skyrail over Toorak Road in Kooyong.

Premier Daniel Andrews described the existing level crossing as "uniquely bad", as the boom gates are down for more than one-third of the time during the morning peak.

And if the level crossing were to remain this would only rise, as the government plans to introduce more train services, he said.