A vehicle hull has a longitudinal blast mitigation duct formed between left and right hull portions. The duct includes a first section oriented at a first angle to a longitudinal reference line, and a second section adjacent to the first section and oriented at a second angle to the reference line. The second angle is greater than the first angle to form a diverging surface for a shock wave travelling from the first to the second section. The blast mitigation duct further comprises a second, rearward-oriented diverging surface for a shock wave travelling rearward along the hull. A rib projects generally perpendicular from a joint between the first and second sections and is configured to initiate separation of the shock wave from the hull, thereby reducing the amount of energy transferred to the hull.