BL Draft Depot slot

Depot Slots
Number of Depot Slots determines how many trains are you able to store into Depot. Depot is useful for assembling trains while waiting for another rail to become available, or to compare different train configurations. You may find it in Depot slots tab of the Trains screen (where you can also purchase additional slots).

The game begins with 5 Depot Slots. Each upgrade gives you 2 more Depot Slots. You may also get extra 2 slots after completeing George. Number of obtainable Depot Slots has been occasionally increased as part of following Game Updates:
 * June 16, 2011
 * June 23, 2011
 * June 30, 2011
 * October 4, 2012
 * October 18, 2012
 * September 19, 2013 ► Slot extensions completely rebalanced - level requirements and/or prices reduced.
 * November 7, 2013 ► Introduced new depot slots #52 - #61 (without completed George).
 * June 5, 2014 ► Various boosts to income, limit and duration and 19 new depot extensions.