The successful bidder for the preliminary engineering design contract, also referred to as 30 per cent design, will be chosen within three-five weeks of bid submission, ADA says. The contract will be carried out over 12-18 months. Up to 10 companies are expected to bid for the project, including firms such as Germany's Dornier Consulting, which completed a feasibility and preliminary design study for the project in June, the US' Parsons Brinckerhoff Internationaland France's Systra.

The design contract will cover two light rail lines running north-south and east-west over a total distance of about 38 kilometres. The project will cost an estimated SR 1,500 million ($400 million). ADA says the 30 per cent study will assist the authority in making a decision on whether the project will be carried out on a design-build (DB), design-build-operate (DBO) or a design-build-operate-finance (DBOF) basis.

ADA is also in the process of choosing a consultant for the project to carry out a study determining the final scope of the LR network. Seven companies, including Dornier and Systra, submitted proposals for the contract last year. A contract award is expected in March, with the study, which is expected to take 15-18 months, due to start in April.

While the 30 per cent design will be based on overground options only, the comprehensive study might reintroduce an underground component.