Planning permission for the main A354 route was granted in April, but approval for Compulsory Purchase Orders necessary to acquire land on the route and works on subsidiary routes has yet to be given.
The decision could make or break the £77M road, which last year secured government funding subject to planning permission. The road is opposed by several of environmental groups because it would run through an area of outstanding natural beauty.
Dorset County Council project manager Matthew Piles said: "From here on in, once the public inquiry is complete, we will wait for any recommendations from the secretary of state.
"Then we will be seeking funding approval from the Department for Transport, and hopefully we'll start construction by summer 2008."
Planning permission for the A354 was granted in April, and a £40M Early Contractor Involvement contract was awarded to Skanska soon after.
The Woodland Trust and government advisors Natural England remain firmly opposed to the scheme.
Natural England regional director Janette Ward said: "The proposed Weymouth Relief Road is an inappropriate and unnecessary response to problems of congestion and accessibility in the Dorchester / Weymouth / Portland corridor, given the permanent damage it will cause to the Dorset area of outstanding natural beauty and to nature conservation interests."
If planning permission is secured, work could begin on site early in 2008 with completion scheduled for 2011.
Government funding was granted after it received assurances that the scheme would be ready for the 2012 Olympics, when Weymouth will host the sailing events.