The　use　of　short-term　load　data　to　extrapolate　or　project　remote　future　maximum　load　has　been　practiced　in　structural　design　code　development　and/or　calibration.　However,　this　approach　has　not　been　adequately　evaluated　or　validated　because　of　the　absence　of　long-term　data,　which　is　important　for　the　structures＇　safety　governed　by　these　codes.　In　this　paper,　the　application　of　such　extrapolations　to　highway　bridge　design　is　studied　by　taking　advantage　of　available　long-term　truck　weight　data　obtained　from　the　weigh-in-motion　technique.　A　new　extrapolation　method　is　proposed　from　the　understanding　of　the　importance　of　the　load　probability　distribution＇s　high　tail.　This　approach　significantly　reduces　the　mathematical　length　of　the　extrapolation/projection　and　thus　increases　its　reliability.　Also　presented　in　this　paper　are　application　examples.　In　addition,　the　extrapolation　process　proposed　is　evaluated　with　quantitative　indexes.　The　application　of　a　temporal　extrapolation/projection　can　now　be　evaluated　by　using　these　indexes　for　its　reliability　and　appropriateness.　©　2011　American　Society　of　Civil　Engineers.