HermiteSpline[{p1x_, p1y_}, {p2x_, p2y_}, {t1x_, t1y_}, {t2x_, t2y_}] :=
{p2x (3 #^2 - 2 #^3) + p1x (1 - 3 #^2 + 2 #^3) + (# - 2 #^2 + #^3) t1x +
(-#^2 + #^3) t2x , p2y (3 #^2 - 2 #^3) + p1y (1 - 3 #^2 + 2 #^3) + (# -
   2 #^2 + #^3) t1y + (-#^2 + #^3) t2y } &

CurveOffset[P_ , radius_] :=  radius {(P[[2]])'[#], (P[[1]])'[#]}/
Sqrt[((P[[1]])'[#])^2 + ((P[[2]])'[#])^2] &

Part::partw: Part 2 of {0.5 (3 Slot[<<1>>]^2-2 Power[<<2>>])+0.2 (1-3 Power[<<2>>]+2 Slot[<<1>>]^3)+(#1-2 Power[<<2>>]+#1^3) 0+(-Slot[<<1>>]^2+#1^3) 0,0.5 (3 Slot[<<1>>]^2-2 Power[<<2>>])+0 (1-3 Power[<<2>>]+2 Slot[<<1>>]^3)+(#1-2 Power[<<2>>]+#1^3) 1+(-Slot[<<1>>]^2+#1^3) 1}& does not exist.