Combine multiple queries into single query
You can use UNION [ALL] to combine rows from multiple queries, as long as the number of columns are the same and the columns are compatible, if not of the exact same types.

SELECT 'Driver' as SourceTable, Driver_No, Name, Available 
  FROM Driver
 WHERE Available = 'Y'
 UNION ALL
SELECT 'Freight', Freight_No, Freight_Wagon_Type_Name, Available
  FROM Freight
 WHERE Available = 'Y'
 UNION ALL
SELECT 'Locomotive', Loco_No, Loco_Name, Available
  FROM Locomotive
 WHERE Available = 'Y';


(added SourceTable column per a_horse_with_no_name's suggestion)

Note that the column names are taken from the first query in the UNION, which means you end up with (SourceTable, Driver_No, Name, Available).  You can always alias them as required.