One of the weird things about safety is that we spend so much effort on safety analysis during design, despite the fact that almost all accidents happen after design is completed. One explanation is that addressing problems by building safety into the design is inherently more effective. A more cynical thought might be that we think of building things as “real” engineering, but looking after them afterwards as a lesser job. In any case it’s a genuine problem that for most systems, there’s disproportionate effort put into making them safe at the point of commissioning given where the risks are coming from through the life of the system. The major exceptions are big structural projects – skyscrapers, dams, tunnels and bridges. These are most dangerous whilst they are still being built. Here the problem can sometimes go in the reverse direction. We put a lot of attention into making sure the finished design is safe, but sometimes forget about the intermediate steps. A bridge, tunnel or building that is structurally sound when complete can still be quite dangerous to build.