A four-mile section of the A591 between Keswick and Grasmere remains closed after it was damaged in a landslide.
Cumbria County Council said it had upgraded a forest road at Dunmail Raise which is wide enough for a small bus but not general traffic.
A spokesman said the service would begin on Tuesday.
A spokesman said there would be a park and ride service with pick up points at Keswick, Legburthwaite and Grasmere.

Wales led after an hour of the first Test before losing 39-21, and succumbed 36-22 in the second after being level 10-10 at the break.
That extended New Zealand's winning run against Wales to 28 games since 1953.
"We just switch off for five-10 minutes and before you know it, New Zealand have pulled away," said Williams.
"But there are encouraging signs that we are playing a more expansive game."
Wales' efforts have had the former Cardiff Blues and Pontypridd player "on the edge of his seat".
But the former Wales captain and British and Irish Lions tourist has been disappointed that his country have not been able to beat an All Blacks team in transition following high-profile retirements.
After the 2015 World Cup, the All Blacks lost record-breaking flanker and captain Richie McCaw, fly-half Dan Carter and midfield pair Ma'a Nonu and Conrad Smith.
"There are two schools of thought at the moment in Wales," said Williams. "One, 'yes we've gone toe-to-toe with the All Blacks and played some great rugby'.
"And the other one is, 'well we've failed again' because they are a team in transition. I don't care how good the players are … I'm a little bit disappointed.
"Whenever you take 700 caps of experience out of a squad, it's got to leave a dent and traditionally they are slow in June.
"On the flip side, you look at our squad - it was the most experienced that's ever left these shores. We didn't have injury worries so I thought this was our opportunity."
The All Blacks have made five starting changes for the third Test, with coach Steve Hansen hoping the risk will have its rewards.
Flanker Elliott Dixon makes his debut at blind-side flanker in place of Jerome Kaino, while George Moala takes over at centre from injured Malakai Fekitoa.
Fly-half Beauden Barrett makes only his eighth All Blacks start in 38 appearances as he takes over from Aaron Cruden, who was injured in the second Test.
Barrett has scored 26 points, including three tries in four appearances against Wales.
Two of those tries came in a 15-point haul as New Zealand beat Wales 34-16 in Cardiff in 2014 in his previous start against Warren Gatland's side.
Barrett crossed for his third try against Wales in Wellington last weekend.
Charlie Faumuina takes over from Owen Franks at prop and Julian Savea returns on the wing in place of Waisake Naholo, who drops to the bench.
Injury has forced out veteran Wales prop Gethin Jenkins as well as lock Bradley Davies.
Rob Evans is back at loose-head prop, while Gatland brings in Tomas Francis at tight-head as Samson Lee is relegated to replacement duty.
Gatland, a leading candidate to return to New Zealand as British and Irish Lions coach in 2017, wants his team to stop 'shooting themselves in the foot'.
If so, Williams, who was coached by Gatland and Hansen in a 100-cap Wales career says the Dunedin encounter "could well be" the one in which his countrymen end 63 years of hurt.
Referee: Jerome Garces (France)
Assistant referees: Jaco Peyper (South Africa), Andrew Lees (Australia)
TMO: George Ayoub (Australia)
A shuttle bus service is being put in place to help passengers stranded after the collapse of a major road during Storm Desmond.
[NEXT_CONCEPT]
Former flanker Martyn Williams hopes Wales can avoid the pitfalls of their two previous defeats by New Zealand in the third and final Test on Saturday.