According to a preliminary report by the NTSB, a Republic Airlines Embraer 170 RJ and a Skywest Embraer Brasilia turboprop "nearly collided in the intersection of Runway 1L and Runway 28R" at SFO at about 1336 PDT on May 26.
The Skywest Brasilia had been cleared to land on Runway 28R, crossing the runway threshold at 1335:13. The Republic 170 had been cleared onto Runway 1L about one and one-half minutes earlier and was cleared for takeoff at 1335:12, just one second before the Brasilia crossed the threshold of 28R.
In an SFO tower tape recording, an aural AMASS warning sounds at 1335:40 as the local controller
was communicating with the crew of an uninvolved aircraft. Four seconds later, at 1335:44, the controller yelled at the Skywest crew, who had just touched down, transmitting, "Uh, Skywest HOLD HOLD HOLD," in an attempt to get the pilots to stop short of Runway 1L.The Skywest crew applied maximum braking, but their Brasilia came to a stop in the intersection :censored: of 28R and 1L as the Republic crew was on takeoff roll and heading straight toward them. "As this was occurring, the captain of the Republic [aircraft]
took control of the aircraft from the first officer 
, realized the aircraft was traveling too fast to stop and initiated an immediate takeoff," according to NTSB. The Skywest crew estimated the 170 overflew their Brasilia by 30 to 50 feet; the Republic crew estimated the two aircraft got within 150 feet of each other.The SFO AMASS uses radar to track aircraft on and near the airport surface, providing conflict detection and aircraft information to controllers. NTSB noted that the system is able to detect conflicts between aircraft using the same runway, "and, following a software modification that was installed on Feb. 17, 2007, the system also is able to detect conflicts between aircraft using intersecting runways."