Additional capacity is accomplished by breaking up a couple of Surfliner trainsets to add their cars to the others. The missing trainsets are then accommodated by bringing out those old single level cars (with an occasional appearance by the Great Dome).
Yesterday, train #582 (southbound from LA) was so cursed. It was a sorry mishmash of cars and livery. Pulled by a regular grey Amtrak engine (not a sleek blue Surfliner engine), there were seven single level cars: two of the flat sided Horizon model and 5 of the cigar-like, rounded Amfleet, brought up at the rear by a Cascades "cabbage".
That is, an ex-locomotive in the distinctive paint job of Amtrak's Cascade line, with its engine removed, that now serves as a combination cab car (to drive the train: a "non powered control unit" ) and baggage car. Cab+Baggage = Cabbage.
I am not making this up.
The problem with these cars is that they are single level, designed for raised platforms. They are also old and uncomfortable, with worn out seats and lousy suspensions. Worst of all, the doors are manual. At every stop, the conductors must open the doors and lower the rickety folding steps. Since there are only three crew on the train, that means most doors don't open (unlike the regular Surfliner trainset, which has two efficient automatic doors in each car). So you have to queue up by just a few doors to get on and off, which makes for delays...and makes the old trainset inevitably late.
Everyone hates the old trainsets which are rotated through the different services so that the pain is equally distributed. Racing season lasts six weeks.