They command some of the world’s most spectacular views, but fast and heavy traffic can make them a nightmare for cyclists.
Now plans are being devised to enable riders to divert from busy Highland main roads to new off-road cycle paths.
The national cycle network (NCN) covers much of Scotland on segregated routes and quieter roads, but there is a huge gap across the Highlands between the Great Glen and the Western Isles – the largest area of the UK without an official route.
Cycle route developer Sustrans is about to launch a feasibility study into new paths for riders to reach the West Coast and islands.
These are expected to include routes to ferry ports such as Mallaig and Ullapool.
Sustrans Scotland head of network development Tom Bishop said: “The NCN is a valuable asset to local economies and is a fantastic driver for walking and cycling tourism – particularly in the Highlands and Islands.
“However, we and our partners are aware of the gap in the network routes between the Caledonia Way (Campbeltown to Inverness) and the Hebridean Way in the Outer Hebrides.
“In order to address this, a high-level feasibility study is set to commence to identify potential multi-modal routes [cycling and walking] from the Great Glen which could form a gateway for people to walk and cycle to the islands.
“We hope the results will help to inform the creation of new routes in the area, helping to make it easier for more people to discover Scotland by foot or bike.”
A community group in Skye is already forging ahead with plans for cyclists to bypass the A87 between the Skye Bridge and Broadford.
The island’s main gateway is becoming increasingly busy as it struggles to cope with the mounting tourist influx.
Campaigners and the Broadford & Strath Community Company want to restore the adjacent old road as a safer and more attractive route for riders.
Cyclist Andy Neison, who is working with the company on the project, said: “I regularly commuted on that stretch of road until a few years ago.
“The view over the islands, up the Inner Sound and on to the mainland beyond is grand.
“The road surface, speed and proximity of cars, vans, buses, campers and lorries is not so enjoyable.
“Some drivers are considerate, others not so.
“The opinion amongst those who drive or cycle it is the same – it’s fast and dangerous.”
Neison said locals had made their first attempt to re-open the long-disused old road in 1995 as it was disappearing under vegetation.
Residents are now being consulted over the revived plans.
Neison said: “Feedback to our survey shows what people wish is a safe path.
“For it to be safe, functional and effective, we believe it needs to be on the north side of the trunk road between the airstrip and the bridge – a distance of some seven miles – that would utilise large sections of the old road.
“These would be joined up/augmented by new sections to provide a route that takes users off the main road.”
Neison said existing roads, including the A87, would be used through Breakish and Broadford.
“Our work has really just begun in delivering what we hope will be one path in a network of many.”
Markus Stitz, founder of cycle tourism developer Bikepacking Scotland, said there was also potential to use old heritage paths “to explore the regions currently not covered by NCN routes”.
These could include forestry tracks, which form part of the Wild About Argyll trail between Helensburgh, Tarbert and Port Appin.
Stitz said: “A similar approach could work in the region between Great Glen and Western Isles to make this more attractive for cycle tourism.”
Transport Scotland will double annual spending on cycling and walking to £80m this year, but it gave little indication of any extra cash for new rural routes.
A spokesperson said: “Our focus will be on making our towns and cities safer and friendlier with more segregated infrastructure where appropriate, improvements to the public realm and putting people before motorised vehicles.
“This will allow us to continue to build an active nation, boosting investment in walking and cycling and ensuring that as many people as possible can enjoy the environmental and health benefits of active travel.”