> A lot of hills have passing lanes _specifically_ for this issue. You'll often see heavy truck that's not only slow uphill but also slow downhill, in some cas

> A lot of hills have passing lanes _specifically_ for this issue. You'll often see heavy truck that's not only slow uphill but also slow downhill, in some cases even more so - because it can't afford to build up speed above what its breaks can handle. And these passing lanes are _never_ in downhill direction.