That climb definitely calls for assistance. My wife and I have taken on some decent climbs in the past but we don’t even come close to the speed of vehicles on the way back down. One in particular is Sunwapta Pass. It’s a 10 km climb to reach the pass but the ride back down is well worth it. This was part of a 70 km ride that eventually took us to the Columbia Icefields and back.
Another is the road up to Mt Edith Cavell in Jasper National Park with some pretty spectacular views closer to the top. With very little to no side shoulder to speak of and busy summer traffic, it can make for an interesting ride.