the application 9 (Private bus), 10 (Public bus) — Passenger vehicles with 20 seats or more. The driving tests for both are the same, and class 4 (private light bus) licence is issued automatically at the same time when applying class 9, 10 licences after passing the test. In addition, class 5 (public light bus) licence can be applied after taking an additional Pre-service Training Course for Public Light Bus Drivers. 17 (Franchised public bus) — This is obtained through training within a franchised bus company, for example, Kowloon Motor Bus. The driving test requirement is the same with public bus (class 10), and is only retained with historical interest. A driver passing a test on a franchised bus will be issued classes 4, 9, 10 in addition to 17, and 5 after taking an additional Pre-service Training Course for Public Light Bus Drivers, enabling him/her to drive any public buses, whereas a driver holding class 10 (public bus) licence can also drive franchised public bus. Class 17 exists because the government had to protect the interests of franchised bus companies, in the past, drivers trained by a franchised bus company could only get a class 17 licence, enabling him/her to drive franchised public bus only but not other public buses. This has been relaxed such that a driver passing test on a franchised public bus can get classes 9, 10 in addition to class 17, and original drivers holding class 17 without classes 9, 10 can also apply them for free without taking tests. 18 (Medium goods vehicles) — Goods vehicles with maximum gross weight above and not exceeding . Class 2 (light goods vehicles) licence is issued in addition to class 18 after passing the test. 19 (Heavy goods vehicles) — Goods vehicles with maximum gross weight above and not exceeding . Class 2 (light goods vehicles) and class 18 (medium goods vehicles) licences are issued in addition to class 19 after passing the test. 20 (Articulated vehicle) — Usually refers to vehicle in the form of truck and trailer combination (hence articulated, but not include tow vehicle), total weight between . The driver has to obtain full licence of class 18 (medium goods vehicles) at least before applying. Class 19 (heavy goods vehicles) licence is issued in addition to class 20 after passing the test. 21 (Special purpose vehicle) — Includes street washing vehicles, arrow vehicles, road