Phofsit Daibuun
Phofsit Daibuun (Han-ji: 普實台文; POJ: Phó͘-si̍t Dâi-bûn, abbreviated as PSDB) was designed to avoid the use of diacritics (accent marks) or special characters to write Taiwanese. Instead of representing tones with markings, PSDB uses tonal spelling, in much the same way that Gwoyeu Romatzyh (GR) does for Mandarin.
PSDB suffers from the same drawbacks as GR in that the system seems excessively complicated and counter-intuitive to newcomers - instead of graphically representing tone contours, the reader has to assimilate some letters as tonal components - and these letters chosen to represent tones are different depending on the vowels used.