The reason intermodal trains increase urban congestion is because all of those containers have to use a drayage service to get the container to its final destination. Drayage means a truck and chassis is hauling the container and, as far as traffic congestion is concerned, each container hauled across the country becomes another 18-wheeler in an urban area.
My experience driving I-80 across Nebraska to Denver is that there is no congestion to relieve on the long-haul highways. But in Chicagoland, I-55 is pretty well gummed up now even during the off hours. I live in a western suburb. I used to use I-55 to go downtown to avoid I-290, which became a disaster years ago. Since I go downtown to take pictures only on Sundays, I now take Ogden to 31st Street to avoid I-290 and I-55.
It is a shame that CSX has torn up all of the routes between Chicagoland and Indianapolis and points south. I-65 is a long-haul highway that is congested. Since CSX did tear up the Monon, the state of Indiana needs to get some of its cut of the Federal highway pie and add a third lane to I-65 all the way between "the region" and Indianapolis. I now take I-355 to I-57 to US-52 when I go to Indianapolis or Atlanta to avoid I-294, I-80, and I-65. (Actually, Hunter Harrison killed a lot of CSX intermodal service, along with other railroad services, because he quit "switching containers" at their North Baltimore Yard and backed out of expanding a tunnel in Baltimore to handle dual-stack trains.)
This is what intermodal trains cause, not prevent, in the urban area --- lots of trucks on the local roads.
After railroad freight houses became obsolete, Santa Fe allowed JB Hunt to use their land in the southwest part of Corwith Yard for a regional terminal. Containers headed to California (both southern and Bay Area) can be loaded in Corwith. But containers and/or trailers headed to the pacific northwest using the former CB&Q route along the Upper Mississippi to the former Great Northern route must leave from Cicero Yard. I have wondered if JB Hunt's traffic used rubber or steel wheels between Corwith and Cicero. Steel wheels means that they load a cut of freight cars in Corwith and deliever that cut to Cicero before departure time. Rubber wheels means that all of the containers are drayed to Cicero. One Saturday, while checking out Cicero yard from the Metra station, I got my answer --- rubber wheels. These are the trucks I saw going to Cicero while I was there.
Hopefully, the recent CREATE WA4 Project allows BNSF to switch from rubber wheels to steel wheels for this local truck traffic.
My observations have been that four-bay cars carry plastic pellets whereas flour is carried in five-bay cars. So these cars probably are for Phoenix Closures.
84 Lumber is still rail served.