Unlike other automakers, Tesla doesn't have decades of manufacturing experience. But Tesla says its Fremont factory was able to achieve industry-average safety last year, despite an increase in production.

Tesla's total recordable incident rate improved nearly 25 percent in 2017 compared to the previous year, said Laurie Shelby, Tesla's vice president of Environmental, Health, and Safety, in a new blog post. Nearly two-thirds of incidents involve ergonomic issues caused by repetitive tasks. Tesla anticipates the incident rate will drop to below average this year with the help of the Model 3 assembly line, which Tesla says was built to reduce stress on workers.

Tesla slashed not only the rate of injuries but also the severity of injuries between 2016 and 2017 all while increasing vehicle production by 20 percent. Shelby says that safety at is factory is "light years" better than when the factory was operated by Toyota and General Motors until 2010. Under Toyota and GM leadership, the factory had an average recordable incident rate of 12.6 between 2003 and 2009, and in each of these years, the numbers were worse than the industry average. However, Tesla recorded a rate of just 6.2 last year. In the long term, Shelby says Tesla is capable of operating the safest factories in the world.

To keep workers safe, Tesla implements feedback from employees. One example Shelby gives is a zero-gravity ergonomic chair used when workers install parts in the Model 3. An employee came up with the idea of adding a safety device so that no one would walk behind it and become injured.

In the past, Tesla has come under criticism for safety conditions in its factories. In a letter from a group of factory workers to Tesla board members, employees complained "accidents happen every day" and "severe incidents frequently impact morale and cause delays in production. " Just before this letter was issued, a worker safety organization named Worksafe came out with a report on work-related injuries at Tesla. It found that in 2015 Tesla's total recordable incident rate hit 8.8 percent, or 8.8 injuries per 100 workers. Not only was that 31 percent higher than the industry average, it was also higher than injury rates at slaughterhouses and sawmills.

Tesla says it's not only improving safety but also efficiency. It has been able to reduce the number of labor hours needed to build a vehicle by 33 percent since early 2016. While it once took three shifts and considerable overtime to make the Model S or Model X, it now takes just two shifts and a small amount of overtime. That's despite the fact Tesla built a lot more of these vehicles last year.