the Advanced Detachment of the People's Liberation Army entered Hong Kong. Their vehicles were assigned a series of AD-prefixed registration plates, but continued to display their Mainland Chinese registrations whilst in Hong Kong. Some prefixes are reserved and have special meanings. As of February 2023, the current allocated prefix is YM. A new scheme will be required following the exhaustion of the current two-letter prefix system when it reaches "ZZ", but it has yet to be announced. Motorcycles Formerly, motorcycles used a different set of registration marks. Like the marks for cars, the very first numbers had no prefixes. Later, marks with a single-letter prefix were issued. For example: "B 281", "C 367", &c. The separate issuance system of registration marks for motorcycles has been discontinued and merged with the main system. Some registered motorcycles still bear the early marks. Hence, a unique registration mark without letter prefix could be found on two different types of vehicles. Unusual numbers One-letter prefixes "A" prefix for ambulances of the Fire Services Department of the government "F" prefix for fire engines and other vehicles of the Fire Services Department of the government "T" prefix for use by the motor trade, especially on vehicles that are still unlicensed. These plates are unusual in that they are not specific to any vehicle. They are red-on-white and usually displayed in a plastic holder attached temporarily to the vehicle by rubber straps. The 'T' is followed by up to five numerals. Special prefixes "AM" is reserved for government vehicles. "LC" is reserved for Legislative Council vehicles. "ZG" (for Zhù Gǎng 駐港 which means "stationed in Hong Kong") is for the People's Liberation Army in Hong Kong. ZG plates are not issued with the standard fonts seen on civilian plates. The font used is the same as that of Mainland Chinese plates. However, the plates are still black-on-white in the front and black-on-yellow in the rear. "ZM" is used for vehicles registered in Macau which are permitted to enter Hong Kong via Hong Kong-Zhuhai-Macao Bridge. formerly "UC" was reserved for the then Urban Council. Now available to civilian vehicles. formerly "RC" was reserved for the then Regional Council. Now available to civilian vehicles. formerly "HA" was reserved for the Hospital Authority. Now available to civilian vehicles. Letter suffix "T" suffix for semi-trailers and have a prefix up to 5 digits. Letters-only These are specific car numbers with no