Transport experts have warned a Holyrood committee that spending on road improvements must "increase significantly" to bring them up to a reasonable standard in the light of cuts to council budgets.
Chartered Institution of Highways and Transportation vice-president Neil Johnstone told the rural economy and connectivity committee there has been a "decline in the condition of the local authority roads" due to financial pressures.
"It's not sufficient to keep the roads to a decent standard, never mind to improve them to the standard that a world-class economy needs and deserves.
"There's no doubt that the cuts to local authority budgets have contributed to that but equally we do need to see more investment.
"We do believe that the spend needs to increase significantly."
With MSPs asking about how to better fund road repairs and maintenance, Mr Johnstone said: "We do believe that we are in a place where, to unlock the problem, we need to consider pay-as-you-go methodologies."
He argued a road tax linked to how far, or where, drivers travel could work like many modern car insurance policies to raise revenue to be put towards repairing Scotland's deteriorating roads.
On the day dozens of environmental protesters demonstrated outside the Scottish Parliament to coincide with a vote on climate change targets, MSPs also asked about the impact on poorly maintained roads for cyclists and the possibility of using plastic as a road surface.
Suggesting that investment in road infrastructure was "not just about road users", Ms Hilton said: "It's about ensuring more viable public transport options, ensuring that active travel is an option too."
"If we're trying to increase walking and cycling, we've got to do much better.
"There's a very negative perception of the current facilities. We're building lots of new cycle ways but we're not looking after the ones we've got."
Asked by Scottish Labour MSP Colin Smyth about whether waste plastic destined for landfill could be integrated into road surfaces, director of the Asphalt Industry Alliance David Giles questioned the potential environmental benefits of the policy.
Mixing plastic in with the asphalt would potentially provide longer lasting road surfaces and reduce the plastic going to landfill, but Mr Giles argued the concept "needs to be tried and tested".
Explaining that 80 per cent of asphalt is currently recycled, he added: "We do not yet know whether putting waste plastic into asphalt will have an impact in terms of the recyclability.
"The reality is that if we put new materials into the road we have to consider the environmental impacts as well as the performance of these materials."