Driving to Koh Lanta

To arrive by road, the only way is route 4 which goes from  --------- all the way to ------------.  The turn off for Kohl anta is about – miles from Krabi and --- miles from Trang.  It is clearly marked by signs.  It takes about an hour to the ferry from Krabi or Trand, and about 4 hours from Phuket.