At the top of the sign, clashing black and yellow colours have been used to draw the attention of travellers from a good distance away, those who are purposely seeking a wayfinding system. When walking around London, I could immediately spot one of these signs from a good distance away due to the dramatic splash of yellow and the walking man symbol, making this technique very effective.
The font used throughout the sign is New Johnston, while the body text is 12 pt and written in Johnston Light. New Johnston is a redesign of the original London underground typeface. People are so used to seeing this font when traveling the underground (as most Londoners do) that it becomes subconsciously familiar to them, perhaps making this the perfect font to be located on other way-finding signs. This is a simple, sans-serif font, used because this style of type is clearer from a distance and for quick reading. It is more advanced in these areas than a serif font would be.
Considerations have also been given to users with physical difficulties. as the map is positioned at a height easily readable for members of the public who are in wheelchairs. However, not much consideration has been given to visually impaired (though white text on a black background is said to help), as the writing is not overly large and no braille has been supplied.
This wayfinding system has not been designed for children. I certainly don't think that a child would be able to understand it and, after all, it is expected that the parents will do the navigating.