A route map depicting a path from one location to another is a powerful tool for visualizing and communicating directions. However, it can be difficult for a computer to automatically render route maps that meet the four design goals of effective route maps: readability, clarity, completeness, and convenience. Achieving all of these goals requires trade-offs. We survey the cartography, graphic design, and psychology literature for insight about these trade-offs. We then analyze several common route-mapping styles to demonstrate the variables in map design: what information is included, the precision of that information, and the rendering style. This analysis illustrates that hand-drawn route maps are particularly effective. Finally, we describe in detail a design and implementation for computer-generated maps that mimics the style of handdrawn route maps.