Self-driving cars have been backed by the hope that they will save lives by getting involved in fewer crashes with fewer injuries and deaths than human-driven cars. But so far, most comparisons between human drivers and automated vehicles have been unfair. Crash statistics for human-driven cars are gathered from all sorts of driving situations, and on all types of roads. However, most of the data on self-driving cars' safety have been recorded often in good weather and on highways, where the most important tasks are staying in the car's own lane and not getting too close to the vehicle ahead. Automated cars are good at those tasks, but so are humans. It is true that self-driving cars don't get tired, angry, frustrated or drunk. But neither can they yet react to uncertain situations with the same skill or anticipation of an attentive human driver. Nor do they possess the foresight to avoid potential perils. They largely drive from moment to moment, rather than think ahead to possible events literally down the road. To a self-driving car, a bus full of people might appear quite similar to an uninhabited corn field. Indeed, deciding what action to take in an emergency is difficult for humans, but drivers have sacrificed themselves for the greater good of others. An automated system's limited understanding of the world means it will almost never evaluate (评估) a situation the same way a human would. And machines can't be programmed in advance to handle every imaginable set of events. Some people may argue that the promise of simply reducing the number of injuries and deaths is enough to support driverless cars. But experience from aviation (航空) shows that as new automated systems are introduced, there is often an increase in the rate of disasters. Therefore comparisons between humans and automated vehicles have to be performed carefully. To fairly evaluate driverless cars on how well they fulfill their promise of improved safety, it's important to ensure the data being presented actually provide a true comparison. After all, choosing to replace humans with automation has more effects than simply a one-for-one exchange.