Campaigners had previously warned about the prospect of 800 cyclists heading north through the Highlands. Now their fears have been compounded by a second event with as many riders heading south to meet them.
The A82 Partnership, the group campaigning for the upgrading of the trunk road from Glasgow to Inverness via Fort William, has already raised concerns over the Deloitte Ride Across Britain.
The route will take them along the A82 from Crianlarich to Fort William on Friday, September 12 and Fort William to Fort Augustus the next day.
However, Fort William and Ardnamurchan councillor Brian Murphy, who is chairman of the A82 Partnership, has warned members there will be even more pressure at points on the road than they feared.
"On September 13 and 14 a further 800 cyclists (taking part in the Scotland Coast to Coast event) will be descending on us from the north (Nairn) heading for Ballachulish.
"Thankfully, this group will be on the A82 for only a short distance in Fort Augustus and from the Lochybridge roundabout to An Aird." But he added: "This group will cross the group travelling north around Fort Augustus and along the road on the east side of Loch Ness."
Meanwhile, Glenurquhart play Kingussie in the Camanachd Cup Final at Bught Park, Inverness, on September 13, an event that will draw a crowd of at least 3,000 from all over the Highlands but predominately from around Loch Ness and Badenoch, adding, say campaigners, to potential problems.
A local woman said the cycling fraternity was already causing more difficulties for themselves in Lochaber "by their increasing militancy - riding two to three abreast on these tight, winding roads and refusing to let traffic past."
But Jim Mee, managing mirector of Rat Race Adventure Sports, which organises the Scotland Coast To Coast event, said: "The event has taken place on the same route for six recurring years and to our knowledge has received no adverse feedback."
He said they had deliberately kept the route off busy sections of the A82 such as Fort William-Ballachulish, Fort William-Fort Augustus and Fort Augustus-Inverness.
Threshold Sports, which organises the Deloitte Ride, said it had successfully used the route for the past four years.
"We take the engagement of local communities and the safety of our riders very seriously. Although we have no legal obligation to do so since the event is a bike ride, not a race, we make it a priority to inform local police, local councils and highways department a minimum of six weeks in advance. We have done so with the relevant authorities for the A82."
A spokeswoman for Transport Scotland said: "These events are taking place on public roads, to which everyone has access, and our responsibility is to make sure they go ahead safely through joint working with Police Scotland and the organisers. "
Police said they were liaising with event organisers and also Transport Scotland and Bear Scotland, who are responsible for the road.