Information minister Keheliya Rambukwelle said Egis Bceom International of France will carry out a feasibility study and prepare outline designs for the three expressways.
Higher economic and social development has increased traffic in the city requiring more roads, he said.
Extensive ribbon development along existing road made it impractical to widen key roads in the capital.
One elevated highway will run from Colombo's Fort area to Kottawa for 21 kilometres, where it will connect to an expressway to the island's south and an city outer circular road.
The second, also starting from Fort will run 5 kilometres to Peliyagoda where it will connect to an expressway to the country's international airport in Katunayake.
A third elevated highway will run from Colombo's Kirulapone area to Kadawatha and the outer circular road.
Several Sri Lankan universities will also assist in consultancy.