I work around the BNSF transcon, generally the trains I see run this way, Z trains run with stack cars than piggybacks, hot hot Z- trains have mostly pigybacks, Q train is mostly stack with some piggyback on the rear and generally 8-15 autoracks, Q trains tend to get upwards of 7000 feet in length, Q is also on the symbol for the NS roadrailer, and lastly S trains are entirely made up of doublestack cars and are generally very heavy, 120+ tons per operative break. I have seen in Denver M DENLAU (manifest denver to laurel montana, and return M LAUDEN) have double stack cars on the head end headed to laurel and double stack cars on the rear headed back to denver. Rest of the DENLAU being regular manifest cars, boxes, tanks, flats, etc.
Just my two cents
