Road signs in Singapore closely follow those laid down in the traffic sign regulations used in the United Kingdom, although a number of changes over the years have introduced some slight deviations that suit local road conditions (such as fonts). Road signs in Singapore conform to the local Highway Code under the authority of the Singapore Traffic Police. The Highway Code of Singapore Traffic Police is tested during the Basic Theory Test and Final Theory Test at either Ubi, Bukit Batok or Woodlands driving schools. The students are then to find either a school or private driving instructor to learn driving itself. Singaporean road signs depict people with realistic (as opposed to stylised) silhouettes. No official name is given to the typeface used on all official signs, but they are likely based on a bold and narrow variant of the Charles Wright typeface, which is also used for vehicle registration number plates. Since the mid-1990s, signs have been placed on a backing board making them square or rectangular and standardised to a width of 600 mm on most roads and 900 mm on expressways. Prior to the 1990s and after 1964, signs were cut out to their shape (e.g.: round signs were cut to be circular) as in most countries around the world. Prior to 1964, signs were in the pre-Worboys style with a couple of differences. Singapore traffic signs use the English Language, one of the four official languages and the main language in the country. The three others – Malay, Chinese, and Tamil – and also Japanese are also used for important public places such as tourist attractions, airports and immigration checkpoints. Warning signs Warning signs indicate possible dangers or unusual conditions ahead and alert motorists, so they may anticipate the appropriate actions to take. They are usually shaped as triangles with a red border, and mounted on a borderless white backing board, which is similar to the United Kingdom traffic sign. Regulatory signs Regulatory signs either give positive instructions, i.e. Mandatory signs, or indicate a prohibition, i.e. Prohibitionary signs. Many regulatory signs are accompanied by supplementary plates that provide interdependent exceptions to the rule, or indicates additional instruction or information to facilitate understanding of the rule implemented. Mandatory signs Mandatory signs are generally circular with a white border and symbol on a blue background. They usually indicate something all drivers must do (e.g. keep left) or a