Vector data and in particular road networks are being queried, hosted, and processed by many application domains such as mobile computing. However, many hosting/ processing clients such as PDAs cannot afford this bulky data due to their storage and transmission limitations. In particular, the result of a typical spatial query such as window query is too huge for a transfer-and-store scenario. While several general vector data compression schemes have been studied by different communities, we propose a novel approach in vector data compression which is easily integrated within a geospatial query processing system. It uses line aggregation to reduce the number of relevant tuples and Huffman compression to achieve a multi-resolution compressed representation of a road network database. Our empirical results verify that our approach exhibits both a high compression ratio and fast query processing.