diff --git a/docs/dataset_setup.md b/docs/dataset_setup.md
index f0f9a61c..086a42a6 100644
--- a/docs/dataset_setup.md
+++ b/docs/dataset_setup.md
@@ -7,66 +7,87 @@ After logging in you will see multiple archives.
 For the devkit to work you will need to download *all* archives.
 Please unpack the archives to the `~/nuplan/dataset` folder.
 
+## Dataset splits: train, val, test vs. trainval
+
+The download page provides separate archives for **train**, **val**, and **test** splits.
+However, the devkit expects all `.db` files from the **train**, **val**, and **test** archives
+to be placed together in a single **`trainval`** directory:
+
+```
+~/nuplan/dataset/nuplan-v1.1/trainval/
+```
+
+You do **not** need to create separate `train/`, `val/`, or `test/` directories. Simply unpack
+all downloaded split archives into the `trainval` folder. The devkit handles the logical
+splitting into train, val, and test internally using the log splitter configuration
+(see `nuplan/planning/script/config/common/splitter/nuplan.yaml`), which maps individual
+log filenames to their respective splits.
+
+In short:
+- **Download** the train, val, and test archives separately.
+- **Merge** all `.db` files into the single `trainval/` directory shown in the hierarchy below.
+- The devkit's configuration will determine which logs belong to which split at runtime.
+
 ## Filesystem hierarchy
-The final hierarchy should look as follows (depending on the splits downloaded above):
+The final hierarchy should look as follows:
 ```angular2html
 ~/nuplan
 ├── exp
-│   └── ${USER}
-│       ├── cache
+│   └── ${USER}
+│       ├── cache
 │       │   └── <cached_tokens>
-│       └── exp
+│       └── exp
 │           └── my_nuplan_experiment
 └── dataset
     ├── maps
-    │   ├── nuplan-maps-v1.0.json
-    │   ├── sg-one-north
-    │   │   └── 9.17.1964
-    │   │       └── map.gpkg
-    │   ├── us-ma-boston
-    │   │   └── 9.12.1817
-    │   │       └── map.gpkg
-    │   ├── us-nv-las-vegas-strip
-    │   │   └── 9.15.1915
-    │   │       └── map.gpkg
-    │   └── us-pa-pittsburgh-hazelwood
-    │       └── 9.17.1937
-    │           └── map.gpkg
+    │   ├── nuplan-maps-v1.0.json
+    │   ├── sg-one-north
+    │   │   └── 9.17.1964
+    │   │       └── map.gpkg
+    │   ├── us-ma-boston
+    │   │   └── 9.12.1817
+    │   │       └── map.gpkg
+    │   ├── us-nv-las-vegas-strip
+    │   │   └── 9.15.1915
+    │   │       └── map.gpkg
+    │   └── us-pa-pittsburgh-hazelwood
+    │       └── 9.17.1937
+    │           └── map.gpkg
     └── nuplan-v1.1
-        ├── splits 
-        │     ├── mini 
-        │     │    ├── 2021.05.12.22.00.38_veh-35_01008_01518.db
-        │     │    ├── 2021.06.09.17.23.18_veh-38_00773_01140.db
-        │     │    ├── ...
-        │     │    └── 2021.10.11.08.31.07_veh-50_01750_01948.db
-        │     └── trainval
-        │          ├── 2021.05.12.22.00.38_veh-35_01008_01518.db
-        │          ├── 2021.06.09.17.23.18_veh-38_00773_01140.db
-        │          ├── ...
-        │          └── 2021.10.11.08.31.07_veh-50_01750_01948.db
-        └── sensor_blobs   
-              ├── 2021.05.12.22.00.38_veh-35_01008_01518                                           
-              │    ├── CAM_F0
-              │    │     ├── c082c104b7ac5a71.jpg
-              │    │     ├── af380db4b4ca5d63.jpg
-              │    │     ├── ...
-              │    │     └── 2270fccfb44858b3.jpg
-              │    ├── CAM_B0
-              │    ├── CAM_L0
-              │    ├── CAM_L1
-              │    ├── CAM_L2
-              │    ├── CAM_R0
-              │    ├── CAM_R1
-              │    ├── CAM_R2
-              │    └──MergedPointCloud 
-              │         ├── 03fafcf2c0865668.pcd  
-              │         ├── 5aee37ce29665f1b.pcd  
-              │         ├── ...                   
-              │         └── 5fe65ef6a97f5caf.pcd  
-              │
-              ├── 2021.06.09.17.23.18_veh-38_00773_01140 
-              ├── ...                                                                            
-              └── 2021.10.11.08.31.07_veh-50_01750_01948
+        ├── splits 
+        │     ├── mini 
+        │     │    ├── 2021.05.12.22.00.38_veh-35_01008_01518.db
+        │     │    ├── 2021.06.09.17.23.18_veh-38_00773_01140.db
+        │     │    ├── ...
+        │     │    └── 2021.10.11.08.31.07_veh-50_01750_01948.db
+        │     └── trainval  ← place ALL .db files from train, val, and test here
+        │          ├── 2021.05.12.22.00.38_veh-35_01008_01518.db
+        │          ├── 2021.06.09.17.23.18_veh-38_00773_01140.db
+        │          ├── ...
+        │          └── 2021.10.11.08.31.07_veh-50_01750_01948.db
+        └── sensor_blobs   
+              ├── 2021.05.12.22.00.38_veh-35_01008_01518                                           
+              │    ├── CAM_F0
+              │    │     ├── c082c104b7ac5a71.jpg
+              │    │     ├── af380db4b4ca5d63.jpg
+              │    │     ├── ...
+              │    │     └── 2270fccfb44858b3.jpg
+              │    ├── CAM_B0
+              │    ├── CAM_L0
+              │    ├── CAM_L1
+              │    ├── CAM_L2
+              │    ├── CAM_R0
+              │    ├── CAM_R1
+              │    ├── CAM_R2
+              │    └──MergedPointCloud 
+              │         ├── 03fafcf2c0865668.pcd  
+              │         ├── 5aee37ce29665f1b.pcd  
+              │         ├── ...                   
+              │         └── 5fe65ef6a97f5caf.pcd  
+              │
+              ├── 2021.06.09.17.23.18_veh-38_00773_01140 
+              ├── ...                                                                            
+              └── 2021.10.11.08.31.07_veh-50_01750_01948
 ```
 
 If you want to use another folder, you can set the corresponding [environment variable](https://github.com/motional/nuplan-devkit/blob/master/docs/installation.md).