So if Mr Biden goes from Wilmington-Washington on the 19th [or earler date] due to usual pre-inagural events, you can expect disruptions. Now that Monday [18th] is Martin Luther King Jr. Day, so he probably would not travel on that day because he would be disrupting events planned and it is a Federal holiday. Then Tuesday [19th] is a regular work day and may disrupt commuting on the southern end of the NEC, possible out is to do it mid day so less disruptive to a busy short week. Maybe he will travel on Saturday or Sunday? I am trying to go through these posts and did not see a definite agenda.
Whatever, it will be almost as disruptive as if he was the President.
Presidential travel, as mentioned, is disruptive to the area being traversed and as noted not only to ground transportation but air in a moving bubble. One of the reasons that a Presidential visit to a disaster site is counter-productive and should be done only in extreme case [i.e. WTC].
A train, as much as we think better of, is an extra complication to those task is to provide security. Let's face it, it doesn't allow a lot of options, you don't see a steering wheel in the cab.
Someone mentioned the RFK Funeral Train, I am not sure but I believe Penn Central got a two day notice, and arrangements were no where near what would be today and were tragically no where needed then. IIRC, two spectactors were run over in Elizabeth NJ by a north/east bound train and another was electrocuted somewhere else by standing on a box car under the wires. That in addition to no preparation for a coffin inside a business car which was not original planned placement.