diff --git a/src/methods_named_trajectory.jl b/src/methods_named_trajectory.jl
index 4110b10..1f3fa42 100644
--- a/src/methods_named_trajectory.jl
+++ b/src/methods_named_trajectory.jl
@@ -36,6 +36,16 @@ function Base.vec(Z::NamedTrajectory)
 end
 
 
+"""
+    length(::NamedTrajectory)
+
+Returns the length of all variables of the trajectory.
+"""
+function Base.length(Z::NamedTrajectory)
+    return Z.dim * Z.T + Z.global_dim
+end
+
+
 """
     copy(::NamedTrajectory)