tec, I have done plenty of downtown congested area work, just like the picture you have shown. We would indeed shut down the area immediately affected by our operations. That could be as minimal as a single street/parking lot, that allowed us to stage the load and provide a safe emergency diversionary area. There is no necessity to shut down an entire city, simply the limited area affected by our operation.
As we pick the load in the area adjacent to the work site, then the area affected by our operations is minimal at best. That is why we do it that way. As the helicopter enters and exits the area without an external load, there is no restriction on the rest of our operation. We would still have to do it in the early hours of a weekend morning though. This is precisely how we perform these type of missions, and we are typically hauling something much larger than the example posted.
The picture of the glacier is indeed representative of the areas we, again, do lots of work in. Now, the picture obviously presents a limited perspective of the entire area, but from what is visible in that picture, we would stage out of the parking lot, and fly our departures to the right of the lift, and NEVER cross it. Safety is not limited to congested areas. The exact same criteria are considered in every job we undertake.
The point about lifts by cranes is indeed pertinent, as cranes do indeed drop loads and roll over. That is precisely why cranes are not permitted to lift loads over work crews or the public, and why access to work sites specifically excludes the public. Ever seen the general public wandering around a work site next to a crane?
TeeS, the answer to this would be to perform those lifts within the confines of the airfield, or indeed, perform them in some area which limits the possibility of endangering the public.
And TC, we are indeed tasked as the safety advocates for the public, that is our responsibility when performing these missions. It is precisely because we manage the safety aspects of these jobs, that signs such as you suggest are not required. If indeed we do not perform these missions without excluding that risk, then that is precisely the sign that should be required - and the associated liability it implies.
Somehow, I can't see the cable car operator or your insurance company subscribing to that one.