Use this tool, located on Tools Menu > Show Map Editing Tools > Advanced Tools > Cleanup and Conversion Tools, to separate each segment of a polyline into its own polyline. A polyline entity with 10 line segments, for example, becomes 10 polyline entities.

To explode a polyline

1) Select this menu item from the  menu.

2) Select a layer to work with.

3) Draw a window around the polylines to explode. Only polylines on the specified layer will be exploded regardless of which entities are highlighted during the selection.