While trucks are big, and thus, riskier to automate, they are also risky for humans to drive. Even though truck drivers are professionals who drive all day, there are still around 4,000 killed every year in the USA in truck accidents. More than half of those are truck drivers, but a large number of ordinary road users are also killed. Done well, self-driving trucks will reduce this number. Just as with cars, companies will not release the systems until they believe they can match and beat the safety record of human drivers.