There is a growing need for mechanisms to shape the rate of precompressed video for adaptation to network constraints. The motion vector data component in an encoded bitstream might constitute some considerable portion of P and especially B type pictures, yet no technique currently exists to scale it. Motion vectors of neighboring macroblocks tend to be well-correlated in both horizontal and vertical directions. However, the current standards only exploit the horizontal correlations through predictive coding, introducing dependency and thus resulting in a nonscalable representation. In this paper, we propose a new representation and encoding algorithm for the motion vector information enabling the exploitation of two-dimensional (2-D) correlations, and realizing the signal-to-noise ratio (SNR) scaling of an already encoded video object to an alternate (lower) rate - (higher) distortion level. In the proposed approach, the values of the motion vectors are represented in a binary format. Consequently, the individual bit planes of this representation are coded through a novel 2-D hierarchical bit plane encoding scheme. Scaling, when necessary, is achieved by discarding the least significant bit plane(s). Simulations based on MPEG-2 standard demonstrate that up to 20% scaling is achievable without visually noticeable distortion.