Presently, the majority of all suicide prevention barriers on bridges come in one of three forms:
Fence-like metal structures, usually with an inward curve on top.
Safety nets under bridges.
The aim of these barriers obviously is to prevent injury or death by jumping or falling, but there are other factors that also need to be considered. Large bridges are often monuments and serve an aesthetic role to a city as well, one of the biggest problems with conventional barriers is that they tend to be unsightly. In fact, there have been arguments against installing barriers at some bridges, as people believe that such barriers would not really prevent suicides, it would only change the location and perhaps the method of the suicides while turning the bridges into eyesores. In most cases, barriers are installed regardless of the opposition, but it would be better for everyone if an alternative design could be built to look better while still being effective.
Fences are the ugliest forms of barriers and need to be pretty big to be effective. The Luminous Veil was a concept that was meant to be an alternative to regular fences, but the original idea was too expensive. The barrier was completed without being "luminous" at all and in 2015 the idea was replaced with LED lights on the fencing. While it might be better than having a normal fence, it still isn't exactly pretty.
Glass barriers are less sturdy, more expensive, difficult to maintain and could create unforeseen problems like glare and birds might injure themselves flying into them.
Safety nets seem to be the best option thus far, but people tend to get seriously injured when falling into these nets.
My idea is to create a v-shaped structure underneath the bridge, with an opening or mesh at the bottom. The opening at the bottom should be too small for a human or animal to fall through, just large enough for water and small debris to escape. The angle of the walls should be too steep to climb and extend far enough out so that a person can't jump past.
This should be an effective solution that does not have an impact on the views from the bridge and also is not an unsightly and large addition to the bridge. It would also be safer to land on the side and slide to the bottom than getting entangled in a safety net.
One problem I foresee with this idea is that it might act as a catch for junk and debris, but ultimately, it would not be any more difficult to keep clean than a sidewalk. Access points can be installed to allow workers to get to the bottom of the V to clean when needed. This would also allow medical personnel to reach injured people easier than the nets.
Line the fence with double or triple rows of pigeon spikes to make climbing over a nightmare.
People who are determined to commit suicide will still do it, but they will do it elsewhere because bleeding out before the jump takes more guts (just like living does). Attach the spikes so that getting to a good jumping position is impossible.
Pigeon spikes are thin and possibly invisible from afar - making the bridge look less like a prison.