Double Diesel.
A pair of Altamont Corridor Express (ACE) F40PH locomotives - no.s 3102 and 3104 - are seen shoving train 08 over Patterson Pass Road as they descend the former Western Pacific main line into the Central Valley, heading towards Stockton.
Where once there was only one commuter carrier, Southern Pacific between San Jose and San Francisco, today there are three: Caltrain (former SP), Altamont Commuter Express, and the newest, SMART (Sonoma-Marin Rapid Transit).