At Bettyhill General Merchants, a convenience store and post office in a remote village on Scotland’s far north coast, perched above the spectacular dunes of Torrisdale Bay, owner Susan Malone is anticipating the summer tourist season with ambivalence.

“There’s a sense among locals that the situation is going to get worse this summer. We’ve already had a much busier April and May than expected: I don’t think anybody realised how popular this [driving route] would become.”

The shop is on the A836, on the most northerly section of the North Coast 500, the touring route launched in 2015 to promote less-visited parts of the northern Highlands. It has proved phenomenally popular, attracting hordes of campers, classic car drivers and endurance cyclists every year, and with them some unintended consequences.

The inspired rebranding of a road system that had existed for decades as Scotland’s version of Route 66 is a 516-mile loop that starts at Inverness, heads west to Applecross, facing the Isle of Skye in Wester Ross, then turns roughly north up the coast through Durness and John O’Groats and back to Inverness. It incorporates many narrow, twisting roads, including the steepest single track stretch in the UK, at Bealach na Bà.

The NC500 passport, which visitors can have stamped at participating attractions along the way, recommends stops at “windswept beaches and fairytale castles”, as well as distilleries, smokeries and farm shops. According to research for Highlands and Islands Enterprise, the route boosted business by 15%-20% year on year and led to a 26% rise in visitor numbers and a 10% increase in traffic in the first two years.

But this success is tempered by the associated strain on basic infrastructure – road maintenance, toilets and waste disposal– and some locals argue that the route has created a hit-and-run tourist habit that does not benefit small businesses.

Roofing tacks were found to be strewn across the road near Bettyhill on several occasions last year, according to Police Scotland. Malone and her husband both suffered punctures. Although the perpetrator was never found, locals assume that the vandalism was the result of ongoing frustration at tourist traffic.

Malone says: “The tourists don’t know how to use the roads. They don’t understand how to use passing places, and if someone doesn’t let you overtake, you’re stuck driving at 20-30 miles an hour on a road you know well. It’s difficult for emergency services, doctors and nurses on home visits, and people just trying to get to work on time. Or the tourists will stop suddenly because they’ve seen a Highland cow and want to take a picture.”

Some 200 miles away, where the NC500 follows the west coast by Loch Torridan, local photographer Steve Carter posted a picture on social media this week of what becomes a familiar sight over the summer: five campervans crammed into a lochside lay-by near Shieldaig.

“The herding instinct among motor caravans is strong,” Carter joked, but his frustration is palpable. “There’s an extraordinary number of campervans on the roads. They’re mostly rented in Inverness, so people have no idea how to drive them, and particularly no idea how to reverse, and are understandably nervous doing so. Then you have four or five of them driving in convoy, and if they meet something coming the other way the whole road comes to a halt. It’s the one road out of the village, so local access is effectively blocked.”

Villagers and local politicians along the route point out that these are not isolated incidents but a relentless grind that is affecting quality of life for those who live here year-round.

With the camper convoys come high-powered cars and motorbikes. There has been an increase in road accidents across the north of Scotland since the route was launched, and last year four motorists were charged with allegedly racing at speeds of up to 128mph along its roads. Police Scotland says it has since increased patrols and enforcement activity.

Although the NC500 was the brainchild of the non-profit North Highland Initiative, North Coast 500 Ltd became a private company in April 2015. Tom Campbell, its managing director, acknowledges the impact of the increased traffic along the route but says: “Through our online presence, we encourage anyone planning to visit the North Coast 500 to plan ahead and ensure they understand how to drive and ride responsibly, safely and respectfully. It should also be recognised that residents are as likely to be responsible as visitors for negligent waste disposal.”

Campbell emphasises that the route has contributed to unprecedented growth in an area of Scotland that has suffered significant hardship through depopulation and economic decline. “Our annual surveys would suggest that we are achieving this to date,” he says. “We have seen new businesses open in villages, local amenities are open for longer hours, and younger people can see new opportunities to stay in the area.”

Mike Williamson, a councillor in Perth and Kinross, says the NC500 has fundamentally changed the way in which tourists explore the north of Scotland. He is looking to learn lessons as his more southerly area, between Edinburgh and the Cairngorms, launches its own route, the Heart 200, this summer.

“The NC500 has basically changed the tourist market up there, because people are no longer staying for a week but moving on every night,” Williamson says.

Single-night stays can be crippling for B&B owners, who have to do much more changing of beds, and many along the route now insist on a two-night minimum. Many tourists will arrive at a destination late in the evening and leave first thing next morning to get to the next route point, so they do not have time to spend money in local businesses.

“We’ve also got a duty of care to our environment,” says Williamson. “We can see from the NC500 that we need a supportive infrastructure. People want to wake up next to a lochside but they also need somewhere to dispose of their waste and refill their water tanks.”

It’s a scenario that Sutherland councillor Kirsteen Currie knows well. “We have overflowing bins already and it’s only May,” she says. “The grass around parking places is burned by the chemicals from campervan cleaning systems. I’m sick of seeing human faeces at the side of the road.”

Communication is key, says Currie. Like the majority of locals, she is also keen to emphasise the lifeline that tourism provides to rural areas but wants more consultation. “Both the local authority and the NC500 organisation need to allay the fears of local people.”

She wants Highland Council to explore the possibilities of a visitor levy, as well as support for community initiatives to build more designated stopover sites for larger vehicles, with suitable pitches, recycling and water facilities.

Last October, the Scottish government announced the first round of a new Rural Tourism Infrastructure Fund, with £3m dedicated to upgrading toilets, pathways and campervan facilities in key sites around the Highlands, and in February Highland Council announced an additional £1.5m for road maintenance.

“We don’t want anyone to be put off,” says Currie, “and we’re desperate to welcome people but the vast majority of visitors are whizzing past and ticking it off the list, rather than spending time and money in the local community.”