Is it technologically and economically feasible? And if so...

Is it socially and politically acceptable?

Finally, Hiemstra considers other barriers to a technology's adoption, like whether people will actually want to use it, and whether regulatory agencies will allow it. He thinks this is often the most important criterion.

A prime example is self-driving vehicles. In other parts of the world—like Europe—self-driving, autonomous freight trucks have already been deployed, proving their technological and economic viability. But for them to be adopted in the United States, regulators will have to deem them safe, and companies will have to decide if they are worth the war with trucking unions they'd be sure to instigate.

Then there are passenger cars. Will people be happy to hand control over to a computer? Will those in standard cars be ok with robot cars on their roads? Questions like these could take decades to resolve—unless someone like Elon Musk comes along and accelerates the process. That's what makes prediction impossible, but always so compelling.