The preferred route for the Aberdeen bypass will mean the demolition of a school and 19 homes under new plans unveiled on Tuesday.
The bypass is aimed at cutting congestion in and around Aberdeen
Scottish Transport Minister Tavish Scott said the route minimised the impact on the area it went through.
It would pass through the Milltimber site of the city's International School, which said the announcement was a "shock".
Critics have accused ministers of ignoring their views.
Mr Scott said: "I am very aware of the understandable concerns caused by the width of the corridor being looked at and the time taken to narrow this down.
"However, it was important to examine all the options to help us identify a line that had as little impact as possible on people's homes, communities and the environment.
"We have now completed that process and can now confirm the preferred line for the new road.
"This line achieves, as far as possible, our aim of minimising the impact of the road on homes and properties, but I do realise that for some people this will mean that they are still affected."
About £50m has been estimated for the compulsory purchase of property including the school, homes and farmland.
Leader of Aberdeenshire Council, Audrey Findlay said: "The narrowing of the route corridor is welcome progress, particularly as it will bring a degree of certainty to those whose homes may be affected by the proposed route.
"Effective consultation with residents, business people and campaigners is essential as the project advances."
Aberdeen City Councillor John Stewart said: "We are pleased that the minister has ended the uncertainty by announcing the preferred line.
The bypass plans for Aberdeen have caused controversy
"We are aware that the choice will not please everyone, but it will be a relief to the many people whose homes will not now be affected who are living in the previously announced wider corridor."
The 342-pupil International School is currently in the middle of a major building project, with a new sports complex due to open later this year.
The school's director Dan Hovde told the BBC Scotland news website: "Our goal is to make sure the education we provide continues.
"There is a lot of shock, it was a possibility but when you hear the news it hits home."
He added: "The International School of Aberdeen is opposed to any route which could have a major negative impact on the school.
"The school board will be reviewing the proposals announced today by the Scottish Executive, and will issue a further statement when we have fully assessed the implications."
The 46km bypass, which will cost hundreds of millions of pounds, has attracted significant opposition, including more than 1,600 names on an online petition.
Gregor McAbery, of Aberdeen Friends of the Earth, said: "The executive has tried to claim that the bypass will have little impact.
"Yet as well as demolishing houses and a valued local school, the proposed bypass would devastate the countryside, cutting a swathe of noise and pollution through Aberdeen's western green belt."
Shiona Baird, the Green North East Scotland MSP and energy spokesperson, said: "That this project is going ahead at all proves the audacity of executive ministers who still claim to care about communities and the environment."