Why can my units board train but sometimes it can't?

[newbie123]

I dont understand why the option to board train keep dissapearing and reappearing and it seems completely random that some units are able to and some arent able to. Or a unit can board a train this turn but it cant the next.

[btd64]

Did you use up your rail capacity?....GP

[newbie123]

Is it based on the weight?

[Curtis Lemay]

To entrain, a unit must be:

1. Unmoved in the current turn.

2. On an unbroken rail line hex.

3. Weigh less than the remaining Rail Capacity.

Unit weight is shown in the Unit Report. Rail Capacity is shown in the Situation Report.

[sPzAbt653]

Unit weight is shown in the Unit Report. Rail Capacity is shown in the Situation Report.

Also, this stuff is shown on the Info Bar if you mouse over the Blue Highlighted Train Icon [which is not there if the Selected Unit is not eligible].

TOAW III at top, TOAW IV with New UI at bottom. Sadly, in TOAW IV the Original UI no longer displays this useful information.

[Shadrach]

This may sound obvious, but also make sure to check if you already have some units on trains at their destination, that you forgot about. They will use rail capacity until unloaded.

I certainly forget about this all the time [8|]

[larryfulkerson]

Part of my procedure to do my moves is to first redeploy the aircraft
units to better spots as needed, hold down the period key to disembark
all the embarked units on rails, and THEN move the rest of the units.

[mussey]

ORIGINAL: Shadrach

This may sound obvious, but also make sure to check if you already have some units on trains at their destination, that you forgot about. They will use rail capacity until unloaded.

I certainly forget about this all the time [8|]

Exactly. If a player has entrained units from a previous game turn, that is counted against the current game turn's rail capacity. And yes, I too forget about them. Once detrained, the rail capacity is immediately increased.