Put simply, faster roads need bigger signs with larger letters. |
|
The following Information is taken from Chapter 7, The Design of Traffic Signs 2003 and is useful for those who are unfamiliar with x-height regulations. We hope you find the information useful. |
|
|
The basic unit of measurement is the stroke width (sw), which is equal to one quarter of the x-height of the letters. As a general rule, the x-height on any one sign should be the same for all legends. |
|
|
To ensure correct letter spacing when forming a word, the characters in each alphabet are placed on imaginary tiles. The tiles vary in width, according to the size of the character, and have a fixed height which ensures correct line spacing. All design spaces are measured to the edge of the tiles and not to the actual characters, unless special rules state otherwise. Tile outlines must not appear on the finished sign.
The units of measurement when designing a sign is the stroke width (sw) which is one quarter of the x-height and is not necessarily equivalent to the width of any given character.
The tile height for any alphabet is twice the x-height (ie. 8 sw). Thus for an x-height of 250mm the tile height is 500mm. For the two motorway alphabets, where there are no lower case lletters, the units of measurement are still x-heights and stroke widths. Thus if the x-height of the main sign is 300mm the tile height for both the Transport Medium and Motorway alphabets is 600mm.
The alphanumeric characters used on traffic signs are from a specially designed alphabet known as the TRANSPORT ALPHABET. There are two versions:
- TRANSPORT MEDIUM for white characters on a green, blue, brown, red or black background
- TRANSPORT HEAVY for black characters on a white or yellow background.Route numbers on green background signs are yellow and are from the Transport Medium alphabet. Transport Heavy characters use a slightly thicker stroke width than Transport Medium characters.
Transport medium alphabet - light letters on dark backgrounds 
Transport heavy alphabet - dark letters on light backgrounds
Motorway alphabet - for route numbers used on motorway signs
 |
|
| White on blue (permanent signs) | Black on yellow (temp signs) |