Don't know any simple traffic sign recognition algorithm?
Because road signs are known, recognition can be done according to a pattern. The algorithm is needed so that you can figure it out in a very short time and write a program for a smartphone (which OS for a smartphone is not yet known, and, I think, it does not matter).
Potential problem: comparing photos with all road signs may be too long to be processed by a smartphone. Any ideas on this? And maybe this recognition will be short-lived?