Traffic volumes have fallen or remained static on every major east-west road in Melbourne's inner north in the past decade, VicRoads data shows, clashing with government predictions that congestion is on track to rise by up to 30 per cent in the area in coming years.

The Napthine government released a comprehensive report on the impact of its east-west link project on Thursday, including its effects on traffic volumes on many arterial roads.

The report predicted that traffic would increase by up to 30 per cent by 2031 on main roads in the inner north if the $6 billion-$8 billion, 5.2-kilometre link was not built. It forecast that current traffic levels would fall by the same amount under the east-west link, as the new toll road would draw cross-town traffic off clogged local roads.