1. Perishable goods should be carried in refrigerator cars, shouldn't they?
2. The automatic train control facilitates the work of a locomotive driver, doesn't it?
3. George Stephenson built the world's first public railways: the Stockton and Darlington railway in 1825 and the Liverpool-Manchester railway in 1830, didn't he?
4. An impact-resistant windscreen will reduce the risk of injury to the driver in case of any accident, won't it?
5. The construction of new railway lines is always preceded by long and thorough surveying work, isn't it?
6. Long-welded rails have been used on main railways since 1960s, haven't they?