Transport Scotland has officially initiated the bidding process for the construction of the Aberdeen Western Peripheral Route (AWPR).

The major bypass scheme is now being combined with the £100m Balmedie-Tipperty road project under one contract, in order to cut down costs and accelerate the procurement process.

The AWPR/ Balmedie-Tipperty project is expected to improve journey times, reduce congestion and open up wider markets of the north-eastern part of Scotland, as well as deliver benefits to the local and national economy.

This non-profit distribution (NPD) contract is estimated to be worth between £470m and £500m, a figure which depends on whether a third River Don crossing is part of this deal.

Following the prequalification round, Transport Scotland expects to choose four bidders to tender for the road project.

The name of the company that gets qualified for the contract will be announced in August 2013, which the project expected to be completed by spring of 2018.

"Transport Scotland expects to choose four bidders to tender for the road project."

The second phase of the tender will comprise maintenance of the 46km dual two-lane road for three decades.

Interested firms from across the world will have to submit the prequal documents, which are available at the Public Contracts Scotland website, on or before 4 March 2013.

Earlier this month, over 150 delegates from 60 companies participated in the prospective bidders day, where potential contractors and funders were briefed about the project.

Scottish Transport Minister Keith Brown had then noted that over the next three decades, the project is expected create 14,000 jobs and contribute £6bn to the local economy.