- Graphical-Symbols.info
- At $500 for the initial buy-in, and $150/year thereafter, this may seem a steep price, but it is an invaluable
(if sometimes cumbersome) tool. This database contains the entire current set of ISO and IEC symbols
for use on equipment, with most downloadable in at least PDF format. - AIGA/U.S. DOT Symbol Signs
- These 50 symbols were developed in the 1970s, and while not tested as extensively as required by the IEC/ISO guidelines, they were evaluated and many variants of each symbol were examined.
- Map Symbols & Patterns for NPS Maps
- These are the official U.S. National Park Service symbols. There is no indication that any of these have been tested for comprehensibility, but they are generally well known, and include some graphical vocabulary not present in other symbol collections.
- Emergency Management Symbology
- In my opinion, the symbols in this standard are horrible. You should not treat them as an authoritative resource except for projects directly resulting in mapping to be used by emergency managers. None of these symbols have been through the testing required of the international symbol standards bodies, and as a result, I find many of them counter-intuitive and in conflict with existing symbols.
- Official Signs & Icons 2
- For $250, this is perhaps the most comprehensive and accurate symbol clipart library around. It is the
official distribution source for several symbol sets, although it provides no background information about what exactly
each symbol is supposed to be used for. For that, you need the original source documents, such as the IEC and ISO standards. - Manual on Uniform Traffic Control Devices
- This is the official U.S. Government manual on traffic signs and road markings.
Companion Books
- Symbol SourcebookAn Authoritative Guide to International Graphic Symbols
- Published in 1972, this was one of the first comprehensive collections of symbols, and strangely, remains one of the few to date. It was compiled by Henry Dreyfuss–a famous industrial designer responsible for the Model 302, 500, Princess, and Trimline telephones, streamlined trains, the Honeywell T87 circular wall thermostat, and many more iconic designs. Although it lacks the commentary on the interpretation of shapes that Symbol Signs features, it is nonetheless a very useful research tool for discovering existing symbols and metaphors.
- Symbol Signs, by AIGA
- Symbol Signs Repro Art
The complete study of passenger/pedestrian-oriented symbols developed by the American Institute of Graphic Arts for the U.S. Department of Transportation. This 1992 publication includes the background on the origin of the symbol signs committee, and much commentary on the evaluation of each symbol. This background is invaluable in understanding which graphic forms are likely to cause confusion.
This publication includes camera-ready art and instructions on how the symbols are to be used, as well as color-reference plates for the symbols.