We will be leaving Boppard on 31/10 heading toward Cologne. We need to catch a 12:50 train in Cologne (to Amsterdam). I know there is construction on the RB26 line. I want to leave myself enough time for delays. I was looking at the 8:12 departure from Boppard and it has a construction alert saying there will be partial cancellations - I'm not really sure what that means and how that impacts us. The 9:12 train does not have this same alert - is it safe to assume that if we take this time that it will be better. It will still get us there in time assuming no major delays. Thank you for any advice.
The trains departing Boppard at 8:23, 9:12am and 9:39am and connecting in Koblenz with transfers to faster trains apparently have no bulletins, so one would expect them to run as scheduled.
The note on the 8:12 departure indicates the the stoppage is between Mainz and Ingelheim, and train replacement buses will be used around the stoppage, well before Boppard. So just go ahead and book it. If there is a problem, you can always get the 9:12. It does not have the note because that train starts at Bingen, past the stoppage. You are allowed to take any regional train to get to your booked ICE segment, which is at Cologne Messe/Deutz. Remember, your ICE train to Amsterdam departs from Cologne Messe/Deutz, NOT Cologne Hbf. So if your intent is to stopover in Cologne for an hour, you will have to take a local train across the Rhine to Cologne Messe/Deutz (or walk across the bridge).
The timetable as shown on line you can assume is correct. The notices are there because a lot of people looking up times might wonder why they are not seeing the schedule they are used to.
Providing information is hard. Either you provide to much and you confuse some people, or you do not provide enough and you confuse other people...
I would book the 8:23, with changes in Koblenz and Köln Messe/Deutz, even though the way DB is wasting people's time with unnecessarily long transfers is getting ridiculous.
Note that if you miss a connection due to a delay you can just take the next train, and that without even needing to exchange your ticket. Your ticket is for a route, not a train...
Personally, I wouldn't want to spend the whole journey to Cologne on a train like the RB 26, which is overflowing with people who are fans of dirt cheap travel and have half their household goods with them. I would take the RB 26 Boppard dep. 9:12 only to Koblenz, from there the IC at 10:04 to Cologne main station, spend two hours looking around there and then take the S-Bahn across the Rhine to Deutz. This gives you a half-hour time buffer in Koblenz and still leaves three alternatives open in case ther's a problem.