• This idiotic wooden bridge wasn't there from the start! In a trial run, Seattle built it while I wasn't looking. The bridge stops me from raising sea for central houses.
  Other places: the player wants to build a bridge the OTHER way, maybe?
  To avoid this sort of thing: Early in the game, make a round of the towns; note which ones are in danger of building a nuisance bridge (straight OUT from town); block it with a rail on coast! (bulldoze coast 1st)
  

• After a year or two (more in Tropical/Subarctic) of 'town care', your future megacity should begin to look shapely. Continue the good work:

  - lay out more roads. Connect road loops.
  - (in TTd: only if the roads are yours!)
  - start bus No 2, or No 3,4!
  - Extend the most important bus station out to a railway station and/or Airport site outside. You may soon want to transport to another town.

  Maybe use an advertisement? especially if you also have an important industry station within 10, 15 or 20 tiles from the town centre, a small, medium or large advert may actually earn money directly.
  And watch out for opponents! don't let them in!

• What about 'Fund Buildings'? This is rather expensive, so in ordinary games with the emphasis on MONEY I rarely use it.
  But consider this situation:
  Your city has a 5x5 business area, about 800 - 1200 people.
  There's a subsidy on offer to town B, you intend to get that subsidy.

  In this case 'Fund Buildings' might be a good idea. Do it about 2 - 3 months before you get the subsidy, so that the extra big buildings are there for it.
  'Fund Buildings' may give you an extra 20-30 carriagefuls of passengers during your subsidy year. At 2000 - 4000 pounds / carriage transported, you may get back most of the 'Fund Buildings' cost; and have a larger city as the prize.
  

  Your city needs a certain size for this to work. Too small a town will shrink back to it's old size.

- . - . - . - . - . - . - . -

• The methods above are easiest with flat cities. But a hilly one is more challenging and amusing!
  Plan a terrace city, preferably in Bank direction.
  Use the terraces for roads, the houses will be built on the slopes between.
  Some of the road connections can be tunnels, making use of the underground.
  

In a terraced city, it is sometimes practical to replace the small local bus service with a small mini-train service, 1 level down from the city centre, with tunnels under: it's almost a subway! Is the town on level-1? Then use level-0 (sea level) tunnels!

• Use extended station technique to pull the train stations a little out from the city. Use trains with length 2 or 4. Even a length 2 train with just 1 passenger coach is bigger and faster than a bus.
  A Double-headed engine with passengers equals about 2 buses.
  But length 4 trains (2 tiles) are much better! A couple of length 4 trains (2 Pass, 1 Mail, 1 Engine) or (3 Pass, 1 Mail) will keep the city happy for a long long time.

• If you build a closed ring with 2 or more trains, keep them well spaced out; or sooner or later, one train will break down; the others will pile up behind it, and you end up with the Oslo Tramway syndrome:
  No tram for a long long long time ... then they all come together ... together ... together .......

What about my Computer opponents - won't they sneak in and profit from my costly city planning?
Well: Either play without opponents for the time being; or keep a close watch.
Don't leave 2 free tiles beside each other - Take (rail) one of them! Your AI friends ALWAYS want the road depot NEXT to the bus/lorry station.
One good method: place a rail across some of the streets - about 1 of every 2! this will stop Mr AI from building his Bus stop + Depot couple. Remember: he's quite capable of bashing a few houses to get his stations!

Make the streets your OWN! then you might trap their cars by removing roads!

.

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. Cities in TTd - buses - streets
City development in TTd
In TTo, I advised you to build about 3 bus stops in each city, and send bus(es) between them.
In TTd, city growth is not so dependant on LOCAL traffic. Here it's probably better to have 1 big main station per city, with mixed trains from your bus+rail MEGA.
If you want to develop this town faster, make those extra bus stops, with 1..3 buses. Same if you have a city rating problem - the rating increase depends on number of central stations.
If the town already produces quite a few passengers, you can take the majority off to another town, making MONEY; and let the buses handle just a few locally.

Streets: In TTo, I advised you to CLOSE street loops. In TTd: DON'T !!! Unless the closing street tile belongs to YOU!
Reason: once a loop is closed, you can't cut it to walk your extended station out or in. So:
Watch almost-closed loops, and keep these OPEN! Block them with a rail, a depot or something. Or add YOUR half-road on next tile.

Cars can be U-turned in TTd, so road loops for vehicles is not quite so important. Still, the vehicles won't U-turn without help ...

In my MEGA Workshop , I have shown an example of an open-roaded city: lots of roads with good house sites, but few/no CLOSED road loops
This is a good model for future scenarios: I wish they wouldn't make those long loooong intercity roads, which we players can't cut up without cheating!
Scenario alternative: make that city, complete with 4x4 house blocks; then remove the intersections! Leave it to the player to connect these.
I wonder what the AI opponents would do with such a city??

Street network: Since we don't want too many street tiles, avoid 1x1 blocks. These are OK in TTo - u can easily remove the extra road tiles later.
In TTd: let the streets in one direction be spaced with 2 houses between them; in the other direction, variable from 1 to 4,5,6...
Each house block near the centre having contact with 2 streets - seems to be quite enough - more than enough!

BIG houses demand contact with 2 paved streets, or so they say - I've seen many TTd G-Houses which have only 1 street neighbour.
TTd: the TTd BIG houses seem to get (re)built inside the city's business area, even if no proper connected road is next to them!
In cities large enough, I've seen the same Shop+Office be rebuilt several times, in spite of no proper roads in contact with it.
And: NEW houses on grass do not demand 2 street neighbours. These new houses may be rebuilt into G-Houses later.

Watch street BENDS, avoid having them blocked with houses: this is important in TTd too. Wiggly streets lead to inefficient structure. Straight streets are best. So try to build a straight street grid around the city centre (which you maybe can't change).

So maybe the best road strategy for TTd is:
Gradually make all intersections yours; let the city extend it's own roads from your stubs; if the town road makes an unwanted bend, straighten it out.
This way, you get a network of YOUR intersections, from where you can delete and modify roads; and the city's own roads next to those house plots.
Whether this works or not - I haven't enough experience yet; I'm working on it - sloooowly.

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Business Area shrinkage:
Business Area - In the Tropical scenarios it's the streets with a mid-stripe; there's also an 'inner B.A.': roads with streetlights.
In the Temperate scenarios, all the roads have mid-stripes. But the B.A. looks 'paved' when there is one. Further in: 'Tree-lined roads' - I don't know their significance, but they look nice.
The BA - business area - has sizes from 3x3 up - usually odd numbers. 1x1 is not visible. Desert towns are special - they often have irregular BAs - I've seen 9x6!
.










The 2 pictures show a 3x3 and a 5x5 BA; the corners marked with L, R, T, B. Note the inefficient road structures! These towns have not been shaped by a human player.
In the 5x5 one, only 11 of the 25 BA tiles are available for houses! And one of the 11 - the broken tree-tile marked 'L' - has no road next to it.
A simple road cross through the centre of a 5x5 BA would leave 16 house-sites; one would need roads outside to get at the 4 corner sites.

If too many houses are removed, the city will shrink it's B.A. So test this before you bulldoze a building!
With my games I keep a list of important towns, and check how many houses can be deleted before the B.A shrinks.

Note that B.A. shrinkage can happen without your help! If the town itself removes a building, leaving 'bare land', this can start the B.A shrink. Or your opponents might do some city-wrecking ...

Bulldozing a house 'under construction' is less of a risk to the B.A. I've removed 4 houses 'under construction' from a 16-house town, without harm; where deleting 1 ordinary house would start the shrink process.

Business Area expansion: Business areas also grow, but I don't know any method to push this (more bus stops?) - It's a slow random process.
A house being built where there was no building before is a step towards a larger B.A.
In my first Delta North year, the 3..4 most important towns built about 2 new houses each. 2..3 per year would give 8 new houses after about 3-4 years - then the BA would expand, I hope.
After some TT years one sometimes sees cities with huge B.A.s, many small houses, inefficient roads; and not a very big population.
'Fund Buildings' gives the city a temporarily enlarged B.A., but this usually shrinks again after a few months. And it costs a LOT!

. . . .
After some experimenting in the temperate and tropical climates, I believe I have the main algorithm:
a 3x3 B.A. needs 16 houses.
a 5x5 B.A. needs 24 houses.
a 7x7 B.A. needs 32 houses.
a 9x9 B.A. needs 40 houses. ... etc?
My hacking experiences show that a 3x3 B.A. needs 16 houses; but the 16 includes houses bulldozed while 'under construction'; this is why sometimes a 13 house town can have a B.A.

So when selecting which towns to start developing, count the number of houses. Town A with 23 houses is more promising than town B with 19 houses, even if B has a larger population right now! Also check how hard it is to get a good central road structure.

If you need your city to grow SOON, try to plan the city streets so that most of those 3x3 or 5x5 or 7x7 B.A. tiles are HOUSE tiles, not ROAD tiles! Place roads just OUTSIDE the business area, not just INSIDE.
When the BA expands, you can remove some of those 'just outside' roads.

In TTd use main roads either in NS or in EW direction, with just one or 2 connecting roads the other way. A bend which is not an intersection is inefficient!

When trial-building a MEGA station with a large airport, I've seen the business area shrink from 7x7 to 3x3!
Moral: do the trial build, to see how it can be done.
Then progress SLOWLY towards your large Airport plan - note which houses must go - bulldoze them slowly over time, when they come 'under construction'.
After a year or 2, you should be ready for that Airport MEGA, probably without any city shrinkage.

• TTo: my MEGA station's city centre anchor will always be a bus stop! Since I will probably want local bus traffic to a 2nd bus station in the town.
  
• TTd, and a relatively large town: My MEGA station's city centre anchor might well be a lorry stop! I might want to earn early money transporting the passengers out by train; but use a mail van to another local station to help get those city rating points up!
  
• Other reasons for using a lorry stop in the city centre:
  - If my MEGA station has a number of resources, I might want all the train wagons for something else. The mail wagon is rarely full.
  - Without bus traffic, my MEGA station might have passenger ratings 75 - 80%. With 4-year old buses, it stays at 67%.