Businesses have branded the A9 - the main link between the Highlands and the central belt - as "unsatisfactory".
Those surveyed said they found it stressful driving on the A9
More than 60% of companies and organisations surveyed by Highlands and Islands Enterprise (HIE) said the route should be fully dualled.
The A96, which links Aberdeen and Inverness, was also identified as a road which requires major improvement.
Limited sections of the roads have dual carriageway, or crawler lanes to allow traffic to overtake slower vehicles.
The survey was carried out as part of research by HIE to find where future investment in transport should be targeted.
The study's authors, Reference Economic Consultants, probed the perceptions of 74 public sector bodies, businesses organisations and companies in the Highlands, north east and central belt.
The report concluded: "It should be of concern to HIE and other stakeholders that significant proportions of business organisations and companies view the road links to one of Scotland's five cities as unsatisfactory."
Within the region, key concerns about the A9 centred on perceptions that the road was unsafe due to the mix of single and dual carriageway sections.
It was said that the road lacked enough overtaking opportunities and that the build-up of vehicles on some sections made driving stressful and hard work.
Outside the Highlands, the majority of businesses had a negative perception of the A9.
Almost all of them considered the journey from the central belt to Aberdeen to be much better than the trip up the A9 to Inverness because the route was largely dual carriageway.
Nearly three-quarters of those asked said they felt the road quality was constraining development in the A9 catchment area.
The strongest criticism came from companies which do business in the Highlands and Islands but do not have a base in the region.
Some said the A9 was harming the economic growth of the Highlands.
One manufacturer said that in the summer months delays on the road caused time slots for onward air freight to be missed, commenting that this happened "too much".
Tony Jarvis, HIE transport policy manager, said: "This report confirms many conversations we have had with the business community which point consistently to the need to upgrade the A9 and A96 if the area is to develop effectively and sustainable over the long-term.
"Indeed, we firmly believe that upgrading these key routes, as well as their complementary rail services, represent significant projects at a Scottish level - they are a vital part of the nation's transport infrastructure."