Road　digitizing　is　a　labor-intensive　task.　For　reducing　labor　cost,　this　letter　presents　an　effective　semiautomatic　road　delineation　method　based　on　geodesic　distance　field　(GDF)　and　piecewise　polygon　fitting.　The　main　components　of　the　approach　are　optimal　circle　calculation,　soft　road　center　kernel　density　estimation　(KDE),　fast　GDF　generation,　and　piecewise　polygon　fitting　model.　First,　the　adaptive　circular　template　is　proposed　to　automatically　measure　the　road　width.　Next,　the　soft　road　center　kernel　density　is　estimated　for　fast　GDF　generation,　which　supports　the　extraction　of　road　centerline　between　two　adjacent　seeds.　Finally,　piecewise　polygon　fitting　is　used　to　refine　the　road　centerline.　Extensive　experiments　demonstrate　that　the　proposed　algorithm　is　efficient　and　robust　in　road　delineation.　The　proposed　approach　takes　almost　the　same　time　to　extract　any　length　of　road　segment　given　fixed　image　size,　and　no　hyperparameters　needs　to　be　set.　©　2004-2012　IEEE.