Metrolink F125 905 shoves on the rear of weekend service train 751 (Perris to Los Angeles) as the train receives an “approach medium” signal at milepost 43 on the BNSF San Bernardino Sub. This signal tells the engineer to proceed past the next signal not exceeding 40 mph, prepared to “advance on diverging route at next signal at prescribed speed through turnout.” In other words, this train will be switching from Track 2 to Track 3 as it approaches the station stop in Fullerton, 2½ miles ahead. A two-hour late Amtrak 3, the westbound Southwest Chief, is ten minutes behind this train and will also receive an “approach medium” signal, but it will switch to Track 1.
