user: Question: What Type of Tunnel is the Downhill Tunnel?
Columns: ['County', 'Tunnel', 'Type', 'Length (Imperial)', 'Date of opening']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Londonderry', 'Castlerock', 'Rail', '668 yd', '1845 - 1853']
SQL:

assistant: SELECT "Type" FROM "Table" WHERE "Tunnel" = 'Downhill';