I was saying that Fault's idea was the correct idea, that's why I was saying you'd have to change how the bridge was set up so that it covers the "corner". (And that, no, you wouldn't need the floodgate, and the bridge could be one tile shorter, and that bridge should be displayed while in the "up" position.)
Oh, my fault (no pun intended) for misinterpreting you.
Also, I think a one-tile retracting bridge at the corner would be enough to make a switch junction.
With dwarves in carts a horrifying idea came to me. What if we put axedwarves in carts and launch them off ramps at goblin archers? Sort of a primitive drop pod system. We'd have ODST (Orbital Dwarf Shock Troops) thats what.
[...]
Will we be able to designate specific carts for specific dwarves or will it only be a first come first served basis?
You
definately aren't the first to think of that, and even if so you can restrict things with burrows.
EDIT:
There seems to be a lot of confusion regarding how rails work and how they are designated. I hope to clear this up with some thourough examples and walkthroughs.
NOTE: At the moment, this is only my understanding of how they work; while I feel confident in it I am not infallible by any means. I hope to get Toady to verify the correctness of this next Future of the Fortress responce. (Unverified conclusions will be marked in green, verified in cyan.)Example Walkthroughs:
Let's say you're pressed for space but want to fit multiple tracks through this tunnel:
█....█
█....█
█....█
█....█
█....█
█....█
█....█
Well, it's obvious you can fit at least two N/S tracks in:
█X...█
█X...█
█X...█
█X...█
█X...█
█X...█
█X...█
█║.X.█
█║.X.█
█║.X.█
█║.X.█
█║.X.█
█║.X.█
█║.X.█
█║..║█
█║..║█
█║..║█
█║..║█
█║..║█
█║..║█
█║..║█
But you can do better than that, in fact you can fit four full N/S tracks in this tunnel, building them this way:
█║X.║█
█║X.║█
█║X.║█
█║X.║█
█║X.║█
█║X.║█
█║X.║█
█║║X║█
█║║X║█
█║║X║█
█║║X║█
█║║X║█
█║║X║█
█║║X║█
█║║║║█
█║║║║█
█║║║║█
█║║║║█
█║║║║█
█║║║║█
█║║║║█
Now you have four rail lines in a space no more than as many tiles wide.
Conclusion:
Rails designated side-by-side in parallel do not affect each other, and can be placed without leaving a gap in-between.
Suppose whatever the maximum length of track that can be designated at once isn't long enough for you, and you end up with this:
█...█
█...█
█...█
█.╖.█
█.║.█
█.║.█
You might think that merely desinating another N/S rail NORTH of that will work...
█.X.█
█.X.█
█.X.█
█.╖.█
█.║.█
█.║.█
...What's this?! There's a gap in the line!
█.║.█
█.║.█
█.╙.█
█.╖.█
█.║.█
█.║.█
It probably won't have much effect besides being a speed bump, but it looks bad and we want it out of there. So we designate a 2-long N/S rail over the gap:
█.║.█
█.║.█
█.X.█
█.X.█
█.║.█
█.║.█
And now we have a nice and neat, complete rail line!
█.║.█
█.║.█
█.║.█
█.║.█
█.║.█
█.║.█
Conclusion:
In order for straight tracks to link up, they must be designated in overlapping segments.
Suppose we want to have a track come up from the SOUTH and turn EAST just SE of this statue here:
...N...
.......
..Ω....
W.....E
.......
.......
...S...
So then, we start by designating a N/S rail like so:
.......
.......
..Ω....
...X...
...X...
...X...
...X...
After the engraver is finished, the result is such:
.......
.......
..Ω....
...╖...
...║...
...║...
...║...
Now, your next action would probably be to designate an E/W rail this way:
.......
.......
..Ω....
...╖XXX
...║...
...║...
...║...
But wait! Let's see what happens when the engraver is finished...
.......
.......
..Ω....
...╖╒══
...║...
...║...
...║...
That isn't what we wanted at all! Now carts coming from both directions will run off the track and crash. How do we remedy this? Simple, we designate an E/W track like this:
.......
.......
..Ω....
...XX══
...║...
...║...
...║...
Then our engraver comes to link the two tracks...
.......
.......
..Ω....
...╔═══
...║...
...║...
...║...
Perfect! We have the turn we wanted now!
Conclusion:
In order for tracks to turn, E/W and N/S must also be designated in overlapping segments.
Let's say we want to make a simple T-junction next to the statue:
...N...
.......
..Ω....
W.....E
.......
.......
...S...
The natural responce would be to designate the rail in two parts:
...X...
...X...
..ΩX...
...X...
...X...
...X...
...X...
...║...
...║...
..Ω║...
...XXXX
...║...
...║...
...║...
...║...
...║...
..Ω║...
...╠═══
...║...
...║...
...║...
But this won't work. The reason why is that a cart coming from the EAST will not choose a direction to travel in, but instead will just keep barrelling WESTwards off the rails.
Instead, start with a corner:
.......
.......
..Ω....
...╔═══
...║...
...║...
...║...
Then designate a N/S rail all the way up to but not overlapping the corner.
...X...
...X...
..ΩX...
...╔═══
...║...
...║...
...║...
There is no need to leave an empty tile between the end of this rail and the corner.
...║...
...║...
..Ω╙...
...╔═══
...║...
...║...
...║...
Carts coming from the NORTH should be able to jump the short gap between rails and continue SOUTH with no trouble, while carts from the EAST will turn SOUTH as well. Carts from the SOUTH will turn EAST unless going too fast, but it might be very difficult to attempt to make them go NORTH reliably.
Conclusion:
It is possible to make a pseudo-T junction where two tracks 'merge' by carving a rail up to (but not onto) a corner.
EDIT: all verified by Toady!