I was at first going to wonder if HN is going to recycle all of CS history, and whether that was a good thing or not. Now I see it may be necessary. Because yo

I was at first going to wonder if HN is going to recycle all of CS history, and whether that was a good thing or not. Now I see it may be necessary. Because your solution needs more CS thinking. Your carriage cars are not reversible when used in any ratio other than 1:1 because they need an arrow inside to point to the nearest toilet-car. Also, in odd-numbered ratios (3:1, 5:1), you would really need a car with arrows going both ways, starting from the middle of the carriage. Or maybe you are selling a programmable LCD arrow signage for the carriages... There is also one issue with Dijstra's parable: although the new coupling solution doesn't require ever turning carriages around (as long as they are shunted as pairs), it also means carriages cannot be turned around without extra effort. Assuming the turning platforms can only take one carriage, you have a lot of extra work to turn around a pair and get them back together correctly. However, there are track configurations that can turn the paired cars around more easily. In any case, this probably explains why all trains have seats facing both directions: they never need to turn them.