Road signs in Thailand are standardized road signs similar to those used in other nations but with certain differences. Until the early 1980s, Thailand closely followed US, Australian, and Japanese practices in road sign design, with diamond-shaped warning signs and circular restrictive signs to regulate traffic. Signs usually use the FHWA Series fonts ("Highway Gothic") typeface also used in the United States, though some signs on recently completed expressways use "Transport Heavy". Thailand signed the Vienna Convention on Road Signs and Signals but have yet to ratify the convention.