If all software specifications were as finite as bridge specifications you would see a lot better failure rates. A bridge is deployed in a single instance, in

If all software specifications were as finite as bridge specifications you would see a lot better failure rates. A bridge is deployed in a single instance, in a single environment with a specific type and quantity of traffic. Everything about what a bridge does is known and quantified. As a rather direct example, look at the software that runs traffic lights; doesn't really ever fail, every possible state is covered, and as a result we trust with our life that when our light is green, the cross-traffic is red. There's plenty of software that is as reliable as bridges. On the other hand there's a lot of professional engineering that I would trust far less than a web app. Things like high-end cars, sports equipment, rockets, etc. are all signed off by professional engineers but have an incredibly high failure rate.