To run an Assetto Corsa freeroam server — the kind with AI traffic where people cruise, drift, and street-race — you don't use the official Kunos server. You use AssettoServer, a free, open-source replacement built for freeroam. This guide takes you through the whole thing on a Linux host: the three config files, enabling AI traffic properly, the Custom Shaders Patch requirement your players need, and the plugins that make a freeroam server worth joining.
If you've tried to set up "an Assetto Corsa server" before and your AI traffic never appeared, this is almost certainly why: the stock Kunos server can't do AI traffic at all. Only AssettoServer can. Everything below assumes AssettoServer.
Most tutorials for this are Windows-only, out of date, or assume you already know the freeroam-vs-racing split. This one is written for the way a host actually runs it — on Linux, headless — and it's current as of AssettoServer's 0.0.55 release line.
Freeroam or racing — make sure you're building the right thing
Quick sanity check before you start. AssettoServer is a freeroam server: AI traffic, cruising, drift, dynamic weather. It has no qualifying or race sessions and no lap timing. If what you actually want is a race weekend with a grid and results, you want the Kunos racing server instead — stop here and read which Assetto Corsa server you actually need. If you want traffic on the road, read on.
What files does an AssettoServer freeroam server use?
A freeroam server has three config files, all in the cfg/ folder. Getting the right setting into the right file is the thing everyone gets wrong, so here's the map:
| File | Where it comes from | What it controls |
|---|---|---|
cfg/server_cfg.ini | Standard Kunos file | Track, player cap, ports, server name, password |
cfg/entry_list.ini | Standard Kunos file | The car slots — including which are AI traffic (AI= flag) |
cfg/extra_cfg.yml | AssettoServer only | AI traffic, weather effects, plugins, CSP version gate |
There's a fourth, optional file — cfg/csp_extra_options.ini — that carries Custom Shaders Patch options pushed to clients (teleport points, hiding the wrong-way indicator on maps that need it). You'll only touch it for specific maps.
Rule of thumb you should tattoo somewhere: AI, weather and plugins → extra_cfg.yml. Track, players and ports → server_cfg.ini. Car slots → entry_list.ini. If you put an AI setting in server_cfg.ini, nothing happens.
Step 1: Start from a freeroam server, not a racing one
If you're self-hosting, download the latest AssettoServer release for linux-x64 from the official GitHub releases, extract it over a copy of the game's content folder, and you're ready to configure. Note there's no "stable 1.0" — AssettoServer ships as a rolling pre-release line (0.0.55 at the time of writing), which is normal for the project.
On Connect Hosting you skip all of that: order an Assetto Corsa freeroam server and it arrives with AssettoServer pre-installed, the Steam content already pulled, and the dashboard editor wired up. Either way, the configuration below is the same.
Step 2: Pick a track that has an AI driving line
This is the step that quietly decides whether your traffic works. AI cars in Assetto Corsa follow a pre-recorded AI spline — a driving line stored at:
content/tracks/<track>/ai/fast_lane.aip
That spline is recorded by physically driving the route, not generated from the track. No spline, no traffic — full stop. Big freeroam maps like Shutoko Revival Project ship with their splines; a random track you grabbed off a mod site may not have one, in which case AI traffic simply won't spawn and you'll see a "No ai folder found" error.
On our platform we hard-block enabling AI on a track with no spline — the dashboard returns a clear error rather than letting you launch a "traffic" server with an empty road. If you're hand-editing, check for fast_lane.ai or fast_lane.aip in the track's ai/ folder before you count on traffic.
Step 3: The basics in server_cfg.ini
This file is the ordinary Kunos one. For freeroam you're setting the track, the player cap, the name, and letting the ports be. A minimal cfg/server_cfg.ini:
; ---- cfg/server_cfg.ini (Kunos file) ---- [SERVER] NAME=Night Cruise | Traffic | CSP Required ; shown in the server browser CARS=traffic_car;ks_mazda_mx5_nd ; ';'-separated allowed car folders TRACK=shutoko_revival_project_beta ; track folder name CONFIG_TRACK= ; layout subfolder, blank if none MAX_CLIENTS=48 ; player cap (see the note below) PASSWORD= ; join password ("" = open) ADMIN_PASSWORD=change-this-now ; enables /admin in chat UDP_PORT=9600 TCP_PORT=9600 HTTP_PORT=8081 ; lobby/HTTP port — must be reachable REGISTER_TO_LOBBY=1 ; list on the public server browser [PRACTICE] NAME=Freeroam TIME=9999 ; freeroam = one long, looping practice session IS_OPEN=1
A note on MAX_CLIENTS: on freeroam you can go well above a racing grid because AssettoServer isn't bound by the track's pit-box count the way the Kunos server is. But every additional player multiplies your AI cost — see how much RAM and CPU a server needs before you set it high.
Step 4: Define traffic cars in entry_list.ini
entry_list.ini lists every car slot. What makes a slot AI traffic rather than a player is the AI= flag — and this is an AssettoServer feature reading a Kunos file:
AI=none— a normal player slot (the default).AI=fixed— permanently an AI traffic car; a player can never take it.AI=auto— AI while empty, handed over to a player if one joins.
You can't get a busy road out of a handful of cars. Real traffic servers define dozens to a hundred or more AI slots. A trimmed example:
; ---- cfg/entry_list.ini (Kunos file, AssettoServer AI= semantics) ---- [CAR_0] MODEL=ks_mazda_mx5_nd SKIN=racing_01 AI=none ; a player slot [CAR_1] MODEL=traffic_car SKIN=random AI=auto ; AI traffic until a player takes it [CAR_2] MODEL=traffic_car SKIN=random AI=fixed ; always traffic ; ...repeat CAR_3, CAR_4, ... for as many traffic cars as you want density for
Two hard rules: never define more [CAR_x] slots than the track layout has pit boxes, or clients crash on join; and every MODEL you use must appear in the CARS list in server_cfg.ini. On our platform the AI-traffic control generates these slots for you rather than you pasting a hundred blocks by hand.
Step 5: Turn on AI traffic and weather in extra_cfg.yml
Now the AssettoServer-only file. This is where AI traffic actually gets switched on and tuned, where you gate the Custom Shaders Patch version, and where plugins get enabled.
# ---- cfg/extra_cfg.yml (AssettoServer only) ---- EnableAi: true # master switch for server-side AI traffic EnableWeatherFx: true # CSP dynamic weather (rain, transitions) MinimumCSPVersion: 2144 # reject clients on an older CSP build AiParams: MaxAiTargetCount: 3 # AI cars the server tries to keep near each player TwoWayTraffic: false # false = one-directional; true = oncoming traffic MinAiSafetyDistanceMeters: 20 # minimum gap between AI on spawn MaxAiSafetyDistanceMeters: 70 # keep MinAiSafetyDistanceMeters at ~12 or above, or AI brakes the instant it spawns EnablePlugins: # community plugins to load - AutoModerationPlugin - RandomWeatherPlugin AutoModerationPlugin: {} # each enabled plugin gets its own config block RandomWeatherPlugin: {}
Treat the exact numbers as a sensible starting point rather than gospel — read the file AssettoServer generates on first boot for the full set of defaults, then tune. The keys that matter most are EnableAi (nothing happens without it), the entry-list AI slots (density comes from the number of AI cars, not a single setting), and MinAiSafetyDistanceMeters (drop it too low and traffic stacks up and brakes).
On Connect Hosting this is a form: the freeroam dashboard has a Plugins & Weather tab and an AI-traffic control that write these exact keys to extra_cfg.yml for you, so you get the tuning without the YAML surgery.
Once your traffic is running but you want to understand why it's eating CPU — and how to size for it — that's its own topic: AI traffic, and what it costs you in CPU and RAM.
Step 6: Your players need CSP (this isn't optional)
Freeroam depends on Custom Shaders Patch (CSP) being installed on the player's game, not just yours. AI traffic, dynamic weather, teleport points and Steam authentication all rely on it. Minimum versions worth knowing:
- CSP 0.1.75+ and Content Manager v0.8.2297.38573+ for Steam authentication
- CSP 0.1.76+ for WeatherFX (rain and smooth weather transitions)
A vanilla, no-CSP client can't properly join a freeroam server — they'll fail auth or see an empty road with no traffic. Set MinimumCSPVersion to keep out clients too old to render your server correctly, and tell your community up front that CSP is required. Most players in the freeroam scene already run it; new players will need to install it via Content Manager first.
Step 7: Add the plugins that make freeroam social
AssettoServer's plugin system is a big part of why freeroam servers feel alive. Enable a plugin by adding it to the EnablePlugins list; each then reads its own config block. The free, bundled ones include:
- AutoModerationPlugin — auto-kick for wrong-way driving, blocking the road, going AFK
- RandomWeatherPlugin / VotingWeatherPlugin — changing or player-voted weather
- DiscordAuditPlugin — push chat, kicks and bans to a Discord channel
- RaceChallengePlugin — flash-the-headlights street-race challenges between players
- FastTravelPlugin — teleport to defined points; GeoIPPlugin, WordFilterPlugin, and more
A couple of myths to ignore: AssettoServer does not ship a voice-chat plugin, and Steam authentication is a built-in feature, not a plugin. On our freeroam plans every bundled plugin is available in the dashboard toggle list — no downloading assemblies.
Frequently Asked Questions
Why isn't my AI traffic showing up?
Almost always the track has no AI spline. AI cars follow a fast_lane.ai / fast_lane.aip file in the track's ai/ folder, and that has to be recorded by driving — it isn't generated. If the map doesn't include one, no traffic spawns. The other common causes are forgetting EnableAi: true in extra_cfg.yml, or not defining enough AI=auto/AI=fixed slots in the entry list. We cover this in detail in the AI traffic guide.
Do players really need Custom Shaders Patch?
Yes. CSP on the client is what makes AI traffic, dynamic weather and Steam auth work. Without it a player can't properly join a freeroam server. It's a normal requirement for the scene — installed through Content Manager — but do warn newcomers before they try to connect.
How many AI traffic cars should I run?
You can't get real density from ten cars — busy servers define dozens to over a hundred AI slots in the entry list, then shape how many appear near each player with MaxAiTargetCount in extra_cfg.yml. The practical ceiling is 50–100 concurrent AI cars depending on your CPU. Start moderate, watch CPU, and raise it.
Can I run a race on an AssettoServer freeroam server?
No — AssettoServer has no race or qualifying sessions and no lap timing. It's freeroam only. For a proper race weekend you need the Kunos racing server, which we offer as a separate racing product.
Want AI traffic that just works, without touching a single config file? Our freeroam Assetto Corsa servers come with AssettoServer pre-installed and a dashboard editor for traffic, weather and plugins — and we block you from enabling AI on a track with no spline, so you never launch a "traffic" server with an empty road.
