Quote from ATW

FDR data from the Southwest Airlines 737-700 overrun accident on Dec. 8 show the thrust reversers did not deploy until about 18 sec. after the aircraft touched down on Chicago Midway Runway 31C and 14 sec. before it ran through a blast fence at the end of the runway, the National Transportation Safety Board said yesterday. The aircraft continued through a perimeter fence and onto a roadway where it struck two cars, killing a six-year-old passenger in one of them. The captain, who was pilot in command during the landing, told NTSB investigators he could not get the reverse thrust levers out of the stowed position upon touchdown. The first officer, after several seconds, noticed they were not deployed and activated them without a problem, NTSB said. Preliminary calculations show that the aircraft touched down with about 4,500 ft. of remaining runway. Calculations also show that “for the runway conditions and use of brakes and thrust reverser that occurred, the stopping distance without hitting obstructions would have been about 5,300 ft.,” while the actual stopping distance was 5,000 ft.