user: Question: Which Number of vehicles has a Type designation of U5-25 (Bi-directional)?
Columns: ['City', 'Operator', 'Type designation', 'Number of vehicles', 'Width']
Types: ['text', 'text', 'text', 'real', 'text']
Sample row: ['Bonn , Germany', 'SWB', 'K5000', 15.0, '2.65 m']
SQL:

assistant: SELECT "Number of vehicles" FROM "Table" WHERE "Type designation" = 'U5-25 (Bi-directional)';