You can access this dialog from the following:
Creates speed table for the selected alignment. If there is a speed table already defined on the geometry, tool opens this existing table instead of creating new one. Speed table is used for defining speed requirements on different parts of the alignment. Only one speed table can be defined for each geometry, and speed table definition is set for whole alignment, start to end. It is possible to create multiple speed scenarios in each table. If design standards are already assigned to the geometry using geometry tools, tool asks for using this as an input. If this is accepted, speed table is created based on the speed defined in the design standards. However, there is no rule between design standards and speed table, any change in the standards will not affect the table entries. Design standards are only used for initial table creation. Speed table is consumed by other commands. Cant calculations require a speed table to be defined.