External Signage
External signs are those which identify stations. For two main reasons, these signs function in difficult circumstances. Firstly, they are often in very competitive, busy environments where other signs and visual clutter are a severe disturbance to instant recognition. Secondly, the architecture of stations varies so widely, that it is not possible to give hard and fast rules which will apply to all installations.
More than the other categories of signs, external signs affect, and are affected by, the architecture on or by which they are placed. The need for impact and recognition must always be balanced with the need for conservation and appropriateness.
The main elements of the external signs are the roundel and the fascia. Generally, the roundel provides identification of a station and its entrance. The fascia acts as a secondary identification element and gives the name of the station. A roundel must always be present at station entrances, but there will be cases where it is not possible to include a fascia. At interchange stations where the entrance serves more than one transport network, an interchange totem sign should be adopted.
Read about:
1. Roundels
2. Totems
3. Entrance fascia
4. Heritage & external signing

Next: Roundels