I5 is constantly "clogged" with trucks because of market and logistical dynamics, not because of UP's ineptitude. Southbound is a backhaul market from the PNW for trucks, so loads to California go for bottom dollar, some gyppo drivers will take a load that barely coveres fuel. Northbound is heavy with consumer goods and the like which haven't ridden the rails for decades. UP nor any other railroad can offer 48hr door to door on a 1000 mile length of haul. So cheap south, and timely north means the RR just moves the bulk commodities mostly. That fact that southbound is also mostly frozen foods and lumber means that SB on the RR is actually a headhaul, making it even less attractive compared to trucks.