 Complete the following phrase:  Experts expressed concern of the networks operational efficiency. In 2016, Chinese railways carried almost 2 trillion ton-kilometers of freight and over 1 billion passenger-kilometer of passengers, making it one of the worlds most intensively used freight and passenger railway networks in the world. However, the rail staff productivity upon railway track infrastructure index in China is less than 0.05, being the lowest among the countries with significant railway construction. The government also articulated the importance and urgency of assuring the capacity of railway staff, especially their familiarity with telecommunication and signaling testing in the official investigation of the 