SCHEMA:
CREATE TABLE table_name_80 (freight_carried_s_tonne INTEGER, year VARCHAR, road_closed VARCHAR, super_b_capacity_reached_ VARCHAR, _citation_needed_ VARCHAR)
USER:
What is the smallest amount of freight carried on the road that closed on March 31 and reached super B capacity on February 17 after 2011?

QUERY:
SELECT MIN(freight_carried_s_tonne) FROM table_name_80 WHERE road_closed = "march 31" AND super_b_capacity_reached_[_citation_needed_] = "february 17" AND year > 2011