array slows down editing nurbscurve

I am modelling a roller-coaster and used the array modifier to create the track.
Verts:44124 Faces:33976
When I want to edit the nurbscurve blender is responding extremely slow in the 3D view.
Even when I disable subsurf. What more can I do to improve the editing speed.

Can be closed I disable array display modifier now when working in edit mode nurbscurve.

vbo’s active?

vbo was not active.