Twisted graphene monolayers form a sample of two closely spaced two dimensional systems. We have performed transport measurements on such decoupled graphene layers being jointly contacted and conducting in parallel to investigate the properties of charge carriers in both layers. Varying the charge carrier concentration and applying perpendicular magnetic field, the electric field effect, Shubnikov-de Haas oscillations and plateaus in the Hall resistance are observed. At the charge neutrality point, the resistance decreases by 15 percent with increasing temperature from 1.5 to 50 Kelvin. © 2011 American Institute of Physics.