Those guard rails on the trail are terrible - they narrow the path down by almost a metre for almost no reason. My bet is they're gone within a few years because of congestion issues on the trail.
That was my first thought as well. But I think in reality, they are just narrowing the path by a foot or so off the bridge, as most of the angle goes over that big concrete curb. On the bridge, it isn't a metre or even 3 feet, I don't think. Maybe 2 feet. It also makes it look more interesting, and probably does make them stronger