Why does the Beijing-Hong Kong subway recruit people every year?

There is a great demand for employees. With the increasing number of vehicles in Beijing-Hong Kong area, the original crew and train personnel are getting more and more nervous. Therefore, it is necessary for Beijing-Hong Kong Metro to expand the recruitment scale. As a result, the Beijing-Hong Kong subway recruits new workers every year. The main reason for the large number of employees is that more and more people take the high-speed rail.