2011 rule changes - restrictions on front chassis height 03 February 2011
To kerb increasing heights of the front sections of chassis, the FIA has put new limits in place in order to preserve driver visibility and safety. The section between the vertical lines A and B now has a maximum height of 625mm above the reference plane (RP).
FIA Technical Regulation
From 15.4.4 - The maximum height of the survival cell between the lines A-A and B-B is 625mm above the reference plane.