Cities: Skylines II / Guide 01

Road Hierarchy Playbook

The skeleton every city needs. Four tiers, three rules, and the spacing numbers that make traffic solve itself before it ever exists.

Traffic problems are geometry problems that got zoned. Every jam you have ever bulldozed traces back to one decision: a road asked to do two jobs at once. This playbook gives each road exactly one job.

The model is a tree. Locals are twigs, collectors are branches, arterials are limbs, the highway is the trunk. Traffic climbs the tree to go far and climbs down to arrive. Break the tree, and every trip fights every other trip.

One district, fully dimensioned

Tap a tier to isolate it

This is the whole playbook in one drawing: an 800 m arterial ring fed by a highway interchange, split into thirds by collectors, filled with 112 m local modules. Every number on the sheet is explained below. Use the chips to see each tier's job on its own.

ROLEThe tree: local feeds collector, collector feeds arterial, arterial feeds highway.

CONNECTS TOEach tier touches only its neighbors. No skipping.

ZONINGLives at the bottom of the tree, never the top.

SPACING800 m ring · 270 m collectors · 112 m locals

One district cell of a city that will never jam: the highway touches the grid in exactly one place, arterials move traffic across town, collectors gather it, locals hand it to front doors. Eight of the nine cells repeat the detailed module.

Zoom out: the whole city is this, repeated

Six districts, one highway, two interchanges. Every arterial cell subdivides into the same three-collector grid as the sheet above; locals are left as texture here, not drawn individually — once you can place one district, you can place all of them.

Same rule, bigger canvas: two interchanges feed six districts, never one district twice. Arterial columns and rows line up with the 800 m spacing from the sheet above; every cell inside them is the same three-collector grid, and every collector cell is the same 112 m local module, just too small to draw at this scale.

The ladder rule

Only neighbors touch

A road may only connect to its own tier or the tier directly above or below it. Local to collector: yes. Collector to arterial: yes. Local straight onto an arterial: never. Every rung you skip becomes an intersection the big road has to pay for, forever.

The payoff is that intersections sort themselves by size. Big roads keep a few big, well-spaced junctions. Small roads take the hundreds of tiny ones, where stopping costs nothing.

Left: the ladder respected. Locals stop at the collector; the collector meets the arterial at a single spaced signal. Right: skipped rungs. Every crossing and driveway is a place where 20 km/h traffic negotiates with 60 km/h traffic.

Know your four tiers

One job each

Highway

Move between cities and districts

CS2 roads: Highways, two-way highways
Connects to: Arterials, through interchanges only
Zoning: Impossible, and keep it that way
Intersections: None. Grade-separated everything

Arterial

Move across town

CS2 roads: Six-lane roads, divided avenues
Connects to: Highway ramps and collectors
Zoning: Never. Buffer with trees, paths, quays
Intersections: Signals or roundabouts, 250 m+ apart

Collector

Gather and distribute

CS2 roads: Four-lane roads, tree-lined variants
Connects to: Arterials above, locals below
Zoning: Yes. Commercial loves the corners
Intersections: Tees from locals, stop signs, no lights

Local

Front doors and daily life

CS2 roads: Two-lane roads, alleys, gravel
Connects to: Collectors only, in tees
Zoning: All of it: homes, shops, offices
Intersections: As many as you like, they are free here

Speed climbs with each tier, and that is the whole trick: CS2 sims route by travel time. Make the ladder genuinely faster than the shortcut and traffic polices itself. You rarely need to forbid anything; you make the right path the fast path.

Never zone the arterial

The one rule that outranks the others

Zone an arterial and you have not built a fast road with buildings on it. You have built a slow street with delusions. Every zoned cell spawns driveways, and every driveway is a mid-block intersection: cims pulling in and out across three lanes, delivery trucks stopping in the right lane, garbage trucks doing their rounds, moving vans on every simulated first of the month.

Flip the toggle and watch the same 300 m of road under both policies.

CONFLICT POINTS / 300 M20: 18 driveways, 1 stopped truck, 1 four-way

THROUGH TRAFFICBrakes for someone every 15 meters

NOISE COMPLAINTSYes, and land value sinks with them

Zoned: the fast road spends its lanes on parking maneuvers. Toggle to Clean to see the same corridor with zoning moved one block back, facing quiet locals, with a tree buffer eating the noise.

Field note

Already zoned your avenues? Do not bulldoze the city. De-zone the arterial frontage, drop a parallel two-lane local one block back, re-zone facing it, and let the buildings migrate on their own. The corridor heals in a few in-game months.

The numbers that matter

CS2 zoning is 6 cells deep. Everything follows from that.

One cell is 8 m. Zoning reaches 6 cells from the road: 48 m. A two-lane local is 2 cells wide: 16 m. So the perfect residential module is 6 + 2 + 6 = 14 cells = 112 m, local to local, with zoning back-to-back in the middle and not one wasted cell.

The 112 m module. Repeat it between collectors and every zoned cell in the district earns its keep. The centerline of one local road to the centerline of the next: 14 cells exactly.

Measure	Number	Why
Local pitch	112 m · 14 cells	6 + 2 + 6: zero dead cells between parallel locals
Collector spacing	250 - 300 m	Two local modules plus a flex strip fit between them
Arterial net	700 - 900 m	A district cell big enough to live in, small enough to drain
Arterial node gap	≥ 250 m	Signals need storage room, or queues chain from light to light
Highway touches	1 per district	One interchange per arterial cell; more just invites rat-running
Block length	96 - 160 m	Walkable corners without intersection spam

Treat these as defaults, not law. Terrain wins every argument: bend the module around hills and shorelines, keep the ratios, and forget the protractor.

Grow it, do not gold-plate it

Same skeleton at 500, 5,000, and 50,000 cims

You cannot afford six-lane avenues at minute one, and you do not need them. The skeleton is a promise about geometry, not a shopping list. Build every tier as a cheap two-lane road on its final alignment, then upgrade in place with the replace tool as demand shows up. Corridors are forever; asphalt is temporary.

Three ages of one district. The geometry never changes; only the road widths do. Upgrading in place keeps every building, bus stop, and pipe you already paid for.

Draw the full skeleton first, arterial ring and collectors, as two-lane roads. Yes, before the first house.
Zone only the local modules. The ring stays naked. It will look overbuilt for an hour and correct forever.
Upgrade the ring to four lanes when signals start queuing, using replace mode so nothing gets demolished.
Go six-lane divided and add the interchange when the city graduates from town to city. The corridor was reserved on day one, so nothing is in the way.
Repeat the district. New growth gets a new cell on the arterial net, never an extension dribbled off a collector.

The five classic mistakes

Signed, sealed, and posted like the hazards they are

Zoning the arterial

The rule has its own chapter for a reason. If it has a median, it does not get a driveway.

The four-way local

A local that crosses the big road is a rung-skip with a body count. End it in a tee at the collector.

Signals nose to tail

Queues from one light park inside the previous junction and the corridor gridlocks. 250 m minimum.

The one-bridge district

Every trip in and out shares one link. Two connections minimum, on opposite sides, from day one.

The tempting diagonal

A shortcut faster than the ladder becomes the new arterial, through front yards. If it must exist, make it slow.