AssettoServer AI Traffic Setup: extra_cfg.yml and Entry List

To get AI traffic on an Assetto Corsa freeroam server you need three things: EnableAi: true in AssettoServer's extra_cfg.yml, traffic car entries in entry_list.ini marked AI=fixed or AI=auto, and an AI spline (fast_lane.aip) for the track. Once those are in place, the AiParams section controls how dense the traffic is, how fast it drives and how close it spawns to players. Drivers need Custom Shaders Patch to see it properly.

How AssettoServer traffic works

AssettoServer does not run a separate AI program. Each traffic car is a normal entry in the entry list that the server drives itself, following the track's AI spline. The server spawns those cars ahead of players, keeps them within a radius of someone, and despawns them when nobody is near. That is how a server with 30 traffic entries can make a long highway feel busy: the same cars get reused in front of whoever is driving.

So the amount of traffic depends on two numbers: how many AI entries the entry list has, and how the AiParams spread them around. The AssettoServer FAQ is clear that adding more traffic entries is the most important step for denser traffic.

Step 1: turn AI on in extra_cfg.yml

Stop the server and open cfg/extra_cfg.yml. Find the line and set it:

EnableAi: true

A fresh config has it set to false. If you have not set up the server itself yet, start with our Assetto Corsa hosting guide. While you are in the file, check MinimumCSPVersion. Traffic relies on CSP on the client side, so most freeroam servers require a recent build.

Step 2: add traffic cars to entry_list.ini

Player cars use AI=none. Traffic cars use AI=fixed, which keeps the slot for the server's AI only. AI=auto makes a slot that a player can take, and the AI drives it while it is free.

[CAR_0]
MODEL=ks_toyota_supra_mkiv
SKIN=
AI=none

[CAR_1]
MODEL=ks_toyota_supra_mkiv
SKIN=
AI=none

[CAR_2]
MODEL=traffic_sedan
SKIN=
AI=fixed

[CAR_3]
MODEL=traffic_van
SKIN=
AI=fixed

Rules that trip people up:

1. CAR numbers must run in order with no gaps or duplicates. On some maps, such as Shutoko Revival Project, the entry index also decides where a car spawns.
2. Every entry, player or AI, needs a pit box on the track. The total entry count cannot exceed the track's pit boxes.
3. AutoAssignTrafficCars is on by default and treats car models with traffic in their folder name as AI cars. If your traffic pack follows that naming, you can skip writing AI=fixed for each one, but writing it explicitly is clearer.
4. Every traffic car model must also be in the CARS= line of server_cfg.ini, and drivers need those cars installed, the same as player cars. Our guide to adding cars and tracks to an Assetto Corsa server covers packing them.

Step 3: give the track an AI spline

Traffic follows the track's AI line. Freeroam maps built for traffic ship with one, normally as fast_lane.aip. On the server it goes here:

content/tracks/<track>/ai/fast_lane.aip

For a track with layouts, the ai folder sits inside the layout folder. Create the folder if it does not exist. A spline for a race layout follows the racing line, so traffic on it drives like a race car. Use the traffic spline that the map author provides.

If the server hangs while initializing AI splines, the FAQ fix is to rename that ai folder to ai_off so it uses the regular layout spline, then find a working traffic spline.

Step 4: set the session so it never ends

Freeroam should not reset. In server_cfg.ini, keep only a practice session and let it run forever:

[PRACTICE]
NAME=Freeroam
TIME=60
IS_OPEN=1
INFINITE=1

Remove or close the qualify and race sessions. Restart the server and drive out of the pits. Traffic spawns ahead of you as you move.

The AiParams worth changing

These live under AiParams: in extra_cfg.yml. The defaults come from AssettoServer's own config. Change one or two at a time and test.

A denser highway setup looks like this:

EnableAi: true
AiParams:
  MaxSpeedKph: 100
  TrafficDensity: 1.5
  MinAiSafetyDistanceMeters: 15
  MaxAiSafetyDistanceMeters: 50
  AiPerPlayerTargetCount: 10
  TwoWayTraffic: false

Two cautions:

• Do not drop MinAiSafetyDistanceMeters much below about 12, as the AssettoServer FAQ warns. Traffic starts braking hard and bunching.
• TwoWayTraffic only makes sense on maps whose spline has lanes in both directions, such as country roads. On a divided highway it puts cars on the wrong side.

Why traffic is not spawning

Work through these in order:

1. EnableAi is still false, or you edited the file while the server was running and it was overwritten. Stop, edit, start.
2. No AI entries. Check that some entries say AI=fixed or AI=auto.
3. No spline, or the wrong one. Confirm fast_lane.aip is in the right ai folder for the layout you run.
4. The driver is off the spline. AI only spawns when a player is within a few meters of the spline (MaxPlayerDistanceToAiSplineMeters, default 7) and moving. Sitting in the pits or parked does nothing, and players AFK for 10 seconds stop spawning traffic.
5. The driver's CSP is old. The server can run traffic perfectly while one client sees an empty road. Update CSP.
6. The console shows errors. AssettoServer reports config problems at startup. Read the first lines after a restart.

Memory and performance

AssettoServer itself is light. Traffic adds work for the server, not much memory. A small group with traffic on a modest map is fine on 2 GB, and a full server with dense traffic on a large freeroam map fits in 4 GB. Large maps with heavy traffic plus several plugins are the case for 8 GB.

Running it without a PC left on

All of the above is file editing, and it works the same on any AssettoServer install. On a GamezServers Assetto Corsa server AssettoServer is already installed, you edit extra_cfg.yml and the entry list in the file manager or over SFTP, and the live console shows the AI spline loading and any config errors. The server has its own address with its ports open, so drivers find it in Content Manager without anyone setting up a router. If drivers cannot get in at all, start with our fix list for an Assetto Corsa server that is not showing or cannot be joined.

FAQ

How do I make AssettoServer traffic denser?

Add more AI=fixed entries to the entry list first, then raise TrafficDensity or AiPerPlayerTargetCount and lower the safety distances a little.

What is the difference between AI=fixed and AI=auto?

AI=fixed is a traffic only slot. AI=auto can be taken by a player, and the AI drives it while nobody is in it.

Where does fast_lane.aip go on the server?

In content/tracks/<track>/ai/, or inside the layout folder for tracks with layouts. Create the ai folder if it is missing.

Why do I see no traffic when my friends do?

Your Custom Shaders Patch is probably out of date, or you are parked off the spline. Update CSP and drive on the road.

Can I have rush hour traffic?

Yes. HourlyTrafficDensity takes 24 values, one per in game hour, so traffic can thin out at night and build up in the evening.