The United Kingdom Health and Safety Executive states working at heights is one of the greatest sources of fatalities and major injuries in the workplace, accounting for more than half of all fatalities when combined with being struck by a vehicle or machinery.
Believe it or not, it's quite hard to fall from a ladder if you're doing everything right. Stable footing and three points of contact rarely allow for accidents and more than walking along the street does, so why so many injuries? Put simply, people are not following suggested regulations regarding work at height. Whether under their own fault, or that of a pushy employer, employees may rush, balance heavy items as they try to climb, or conduct prolonged work from a ladder.
Of course ladders aren't the only potential source for injury- using unstable or fragile roofs for access is another one common enough to warrant mention from the HSE.
REDUCE THAT RISK!
Prevention is better than cure, as they say, so the best method to avoid injuries from work at height is simply to avoid work at height. Complex structures can be assembled on the ground and raised instead of doing work in the air, and reach poles can be used in place of access ladders.
Okay, you can't always avoid work at height; It has to happen sometimes. In those cases, there are still many different options for mitigating the effect of having employees in the air.
Training- ensure employees know what they're doing. If they're using specific equipment such as rolling ladders, ensure they know how to correctly secure them in the location. The usefulness of fall arrest harnesses becomes negligible if not worn correctly of if attached to an unstable anchor-point.
Ensure Compliance- workers will unlikely always follow their training 100%, opting instead to take shortcuts or save time. If there are no repercussions for acting in such a way, the behavior may become endemic, and the likelihood of accidents skyrockets.
Equipment- make sure it's correct for the job in hand. For a while I worked in a clothes shop where the only means of accessing both the high shelves in the back room and the small attic-storage area was a folding step ladder that didn't have room to open fully in the cramped space. The only way to access the attic was to lean the ladder against the edge of the upper floor and hope it didn't slip.
Maintenance- replace worn down tread on ladders, step stools and gantries. If a ladder has a weight operated braking system, make sure it's properly lubricated and doesn't seize up.
Infrastructure- if working at heights is something which may need to happen a lot, it may be worth installing gantries, safety nets, hand rails or kick boards in areas that are frequented by workers. A secure gantry that protects the whole workforce is far better than each of them having individual fall arrest apparatus.
Okay, now what?
Now? Use your common sense. That's pretty much what this entire node is, boiled down.