Construction experts presented evidence on the second day of hearings for the next stage of Christchurch's southern motorway.
The Environmental Protection Authority is considering a plan to widen part of the existing Main South Road and building a new highway to connect with the first stage of the southern motorway.
The Transport Agency's Canterbury State Highway manager, Colin Knaggs, said on Tuesday the improvements would cut travelling times between Rolleston and Christchurch from 30 minutes to 15 minutes.
Mr Knaggs said the motorway is one of the seven Roads of National Significance and vital to enable economic growth in the region.
Submissions from residents and business owners opposing the motorway would be heard on Wednesday.