If you mean the speed limit, it's:
.limit <speed in km/h>
If you add this to the start of the file:
Options.UnitOfSpeed 1.609344,
it multiplies the default unit of speed (km/h) by that number, which is the multiplication factor to miles-per-hour, meaning that all .limit numbers can then be given in miles per hour. I find that much more helpful when lining up with FreeObj signs.
Also, signal speeds can be set thus:
Route.Signal(0).Set 0, ;Danger - red (0)
Route.Signal(1).Set 15, ;Extreme Caution - Red (25)
Route.Signal(2).Set 35, ;Caution - Amber (55)
Route.Signal(3).Set 60, ;Proceed - Amber-Green (75)
Route.Signal(4).Set 75, ;Clear - Green (unlimited)
HIH.