If you know what city blocks are, then the How is fairly apparent. Of course, everyone has questions at certain points. As for the Why, some people feel they are more organized, and that is a means to maintain organization. As for the When, it depends on how you create them.
#can someone explain how? why? and when to build a cityblocks?
real prairie
sleek flax
- Make a big rail square (like 3x3 chunks) and copy it into a grid, that's it
- Because if your scale huge you may want to duplicate blocks and cityblocks make that easy
- Grid (same-size) cityblocks are useful to make sure you always have space to build in.
If you want 10 ore belts you don't really need blocks, just place 12 parallel smelter rows, use trains to deliver ore, and use huge space below those 12 rows to use the smelted stuff
glass cliff
City blocks are just a different way of organizing your factory, you put parts of your factory into blocks and then process and move things around like a city
It's for more train centric bases if you don't want to do stuff like rail sandwiches or whatever
As for when, it's all a matter of preference
Organize things however you want, some people like blocks, some people like bus, etc
sleek flax
This is LEGO blocks I use
I love legos as they may be whatever size I want at the moment
https://cdn.discordapp.com/attachments/522829709201899551/1226924302428016751/image.png?ex=66c0c8cc&is=66bf774c&hm=be5dbd568e969e03662bdcf67b1d8892a5b0f0bfaf4c80d8773c2b22d9f3ba7e&
https://cdn.discordapp.com/attachments/166489681821827072/1234462443636392036/image.png?ex=66c085bd&is=66bf343d&hm=0e26c8a2c4e72980f9bae95a74690ef5425e4f4324fec9145dd3b540851a608f&
https://media.discordapp.net/attachments/166489681821827072/1230621480782401566/image.png?ex=66c06450&is=66bf12d0&hm=351a76bcd0baec2d57721bfd9dc281dc65a2d58bbac27ca2441e4f8c0f2389ea&=&format=webp&quality=lossless&width=1659&height=1009
https://media.discordapp.net/attachments/166489681821827072/1230619340307431556/image.png?ex=66c06252&is=66bf10d2&hm=343059d8360aa5b8ad27d251603eaf00654d8bfd265839141bec7b31373475a3&=&format=webp&quality=lossless&width=1825&height=1009
glass cliff
what are the question mark stations
real prairie
Prolly unassigned stations. I call mine literally Unassigned until I give them a purpose lol
ruby marten
This is LEGO blocks I use
I love legos as they may be whatever size I want at th...
do you have blueprints for these 
I'd love to have a look on my test world
fervent laurelBOT
sleek flax
@ruby marten
I mostly use just the first 3 (loop (4 loops in same chunk make the whole intersection), straight, and two-stations-over-straight-and-loop (which intentionally breaks a signal on straight so it's safe to overplop them) )
(other stuff I use when I know I need them, e.g. 4-station when 2 is not enough, Phi to reduce train wiggling on straight-loop-straight, large ones when I need lololots of trains (I generally don't use chest storage with them))
median garden
for the city block design, does it require having trains researched? will i have to do the main bus design before its researched? is the city block design for things like making iron or copper plates, or do you do it for manufacturing?
lone aurora
The city block is a vessel. You can fill in any production line you want.
That can be smelting Iron Ore to Iron Plates, making Purple Science from Ores or anything in between.
not having trains would be an issue though. most City Block designs transport stuff between blocks with trains.
median garden
Ohh I see. So I would have to do a main bus, once I have trains I can transition to city blocks
lone aurora
You don't have to do a main bus beforehand. Can do spaghetti or a monolithic design. Or use belts to move stuff between blocks until you have trains.
City Blocks aren't space efficient and take up quite a bit of resources to set up. Generally it's better to do something else before moving over to City Blocks.