limits are signed only in metric (TSRGD 1981) but older signs with height, width and length restrictions may show metric units in addition to imperial. For distances only miles and yards are used. From March 2015, all new height, width and length restrictions must have dual metric-imperial units. Colours Three colour combinations are used on Worboys direction signs depending upon the category of the route. All roads are categorised as either motorways (white on blue), primary routes (white on dark green with yellow route numbers), or non-primary routes (black on white). TSRGD 1994 also prescribed a system of white-on-brown direction signs for tourist and recreational attractions. TSRGD 2002 updated this and introduced a system of black-on-yellow signs for roadworks. TSRGD 2016 is the current version in force. On Advance Direction Signs, as introduced under the Guildford Rules, the background colour indicates the category of route on which it is located. On all directional signs, destination names are placed on the colour appropriate to the category of route used from that junction. A panel of one colour on a different colour of background, therefore, indicates a change of route status. A smaller area of colour, called a patch, surrounds a bracketed route number (but not its associated destination) to indicate a higher status route that is joined some distance away. A patch may only be coloured blue or green. Signs indicating a temporary change, such as roadworks or route diversions, are denoted with a yellow background. Usually, these signs use a simple black on yellow colour code, more complex signage use the conventional signs superimposed onto a yellow background. In some areas, such as the Dartmoor National Park, additional signs and colours are used to distinguish road conditions. In addition to the national colour schemes, the park also uses white signs with a light blue border and text to denote routes suitable for medium-sized vehicles and white signs with a brown border and text for routes suitable for cars and small vehicles only. The park also uses fingerpost signs for routes suitable for local traffic only. These routes are publicised in park leaflets and other media. For ease of reference, the main colour-coding rules may be summarised as below: The colour-coding for panels on signs may be summarised as below: Typefaces Two typefaces are specified for British road signs: Transport and Motorway. Transport is a mixed-case font and is used for