A qualitative comparative study is performed of the performance of three popular spatial indexing methods-the R *tree, R+ -tree, and the PMR quadtree - in the context pf processing spatial queries in large line segment used by the bureau of the census to deal with the road networks in the US. the goal is not to find the best data structure as this is not generally posible. instead, their comparability is demonstrated and an indication is given as to when and why their performance differs. tests are conducted with a number of large datasets and performance is tubalated in terms of the complexity of the disk activity in building them, their storage requirements, and the complexity of the disk activity for a number of tasks that include point and window queries, as well as finding the nearest line segment to a given point and an enclosing polygon.