CausalDriveBench: Evaluating Causal Reasoning in Vision-Language-Action Models for Autonomous Driving
Organizations: Fastcode AI · Indian Institue of Technology Delhi
Abstract
Vision-Language-Action (VLA) models for autonomous driving produce natural-language reasoning alongside predicted trajectories, but whether this reasoning reflects the causal structure of the scene remains untested. We introduce CausalDriveBench, an evaluation framework grounded in Pearl's Causal Hierarchy (PCH) that tests causal reasoning in driving-specific VLAs through structured visual question answering (QA) and alternative-trajectory prediction. To this end, we construct causal scene graphs over nuScenes that distinguish causally active, dormant, and distractor entities, separating perceptual salience from causal relevance. The benchmark spans all four rungs of PCH (association, intervention, and counterfactual along with causal discovery) for QA generation. For the higher rungs, we additionally provide reference trajectories under specified scene modifications, enabling action-level verification that complements reasoning-level evaluation. In total, the benchmark contains 7,285 verified causal QA pairs and 1,000 counterfactual trajectories derived from nuScenes. We evaluate 10 driving-specific VLAs and 3 general-purpose VLMs, and report three findings. First, the best model reaches only 70.6% QA accuracy, and 4 of 13 models score below random chance. Second, comparing each driving VLA to the general-purpose VLM that shares its language backbone, the cost of driving fine-tuning ranges from 2 to 34 percentage points on causal QA, with post-training design explaining the spread. Third, causal QA and trajectory accuracy are statistically uncorrelated across models: under counterfactual prompts, predicted trajectories either over-react or collapse onto the observed-scene baseline. Taken together, these results show that neither fluent rationales nor accurate observed-scene trajectories constitute evidence of causal understanding.
Figures & tables
| Benchmark | Graph | Causal Status | PCH Layers | CF Semantics | Alt-traj GT |
|---|---|---|---|---|---|
| nuScenes-QA [ 30 ] | SG | ✗ | R1 | ✗ | ✗ |
| BDD-X [ 20 ] | ✗ | ✗ | R1 | ✗ | ✗ |
| DriveLM [ 34 ] | QA-Dep | ✗ | R1–R2 | ✗ | ✗ |
| Reason2Drive [ 26 ] | ✗ | ✗ | R1–R2 | ✗ | ✗ |
| DriveLMM-o1 [ 17 ] | ✗ | ✗ | R1–R2 | ✗ | ✗ |
| DriveAction [ 15 ] | Tree | ✗ | R1–R2 | ✗ | ✗ |
| PCH layer | Entity type | LLM-judge axis | ||||||||||||
| Model | Overall | R0 | R1 | R2 | R3 | Active | Dormant | Distractor | Comp. | Spat. | Mech. | Cond. | Cons. | |
| Driving-specific VLAs | ||||||||||||||
| ImpromptuVLA-7B [ 11 ] | 7285 | 69.27% | 66.43% | 59.41% | 85.10% | 66.93% | 69.07% | 63.92% | 71.69% | 1.06 | 1.08 | 1.12 | 0.63 | 1.39 |
| OpenREAD [ 43 ] | 7274 | 63.76% | 70.10% | 48.95% | 78.89% | 61.03% | 69.81% | 60.62% | 60.80% | 1.18 | 1.14 | 1.30 | 0.83 | 1.44 |
| Orion [ 14 ] | 7285 | 57.25% | 25.44% | 76.03% | 66.40% | 52.58% | 30.27% | 53.26% | 78.08% | 0.19 | 0.14 | 0.07 | 0.06 | 0.51 |
| UniDrive-VLA [ 24 ] | 7285 | 54.87% | 63.69% | 29.71% | 68.24% | 60.08% | 65.88% | 53.75% | 47.54% | 1.12 | 1.21 | 1.24 | 0.74 | 1.31 |
| BTE (m) | CTE-R2 (m) | CTE-R3 (m) | |||||||||||||
| Model | Mean | Std | Min | Max | Mean | Std | Min | Max | Mean | Std | Min | Max | |||
| Driving-specific VLAs | |||||||||||||||
| UniDrive-VLA [ 24 ] | 815 | 0.68 | 0.60 | 0.02 | 4.51 | 209 | 2.90 | 1.74 | 0.14 | 8.06 | 791 | 1.96 | 1.60 | 0.04 | 10.49 |
| RecogDrive [ 23 ] | 815 | 1.19 | 0.65 | 0.14 | 6.63 | 209 | 4.30 | 2.21 | 0.44 | 11.66 | 791 | 1.97 | 1.41 | 0.22 | 9.77 |
| ImpromptuVLA-7B [ 11 ] | 814 | 1.27 | 1.58 | 0.00 | 18.45 | 203 | 5.69 | 4.58 | 0.00 | 19.63 | 781 | 2.97 | 2.49 | 0.00 | 15.40 |
| Alpamayo-1.5-10B [ 36 ] | 815 | 1.31 | 1.25 | 0.00 | 6.79 | 209 | 2.70 | 2.16 | 0.01 | 11.90 | 791 | 1.70 | 1.50 | 0.00 | 10.25 |
Appendix figures & tables32 assets
Supplementary material from the paper’s appendix.
Appendix
| Category | Examples |
|---|---|
| EGO | The ego vehicle itself (unique, exactly one per scene) |
| OTHER_AGENT | Cars, trucks, buses, pedestrians, cyclists, active emergency vehicles - any entity whose future state can change by its own volition |
| TRAFFIC_CONTROL | Signals, signs, stop lines, crosswalk markings - entities that impose a codified traffic regulation |
| ROAD_OBSTACLE | Construction cones, temporary barriers, debris - inert, localised entities requiring only spatial avoidance |
| Effect type | Description | |
|---|---|---|
| GRANTS_PROCEED | Signal or sign permitting ego to enter a region (discrete, permits) | |
| INHIBITS_PROCEED | Entity blocking or prohibiting ego from entering a region: yielding, obstruction, gap waiting (discrete, prohibits) | |
| CONSTRAINS_LONGITUDINAL | Entity modulating ego’s speed or acceleration within its current trajectory: lead-vehicle following, speed limiting (continuous, speed axis) | |
| CONSTRAINS_LATERAL | Entity modulating ego’s heading or lane position: lateral bounding, evasive steering (continuous, heading axis) |
| Type | Rung | Format | Description |
| Active-element types: CaLM causal scenarios over active subgraphs | |||
| CaI | 0 | M | Causal Identification. Identify which visible element is currently constraining ego. |
| CA | 0 | M+B | Causal Attribution. Trace a chain of causal influence from a distal element through a mediator to ego. |
| CB | 1 | B | Collider Bias. Apply explaining-away: when two independent causes share ego as a collider, learning one reduces the necessity of the other. |
| CoI | 2 | M | Confounder Identification. Identify a shared cause that links multiple active influences on ego. |
| BAS | 2 | M | Backdoor Adjustment Set. Identify the complete set of variables to control for when isolating one element’s effect on ego. |
| Structure | Discovery (R0) | Association (R1) | Intervention (R2) | Counterfactual (R3) |
|---|---|---|---|---|
| Direct ( ego) | CaI | – | – | CR, SC |
| Chain ( ego) | CA | – | CDE | NIE, NDE |
| Confounding ( { ego}) | CaI | – | CoI, BAS, CDE | CR, NIE, NDE, SC |
| Collider ( ego ) | – | CB | – | NC |
| Graph Structure | QA pairs | % of total |
|---|---|---|
| Direct ( ego) | 1,646 | 22.6 |
| Collider ( ego ) | 359 | 4.9 |
| Confounding ( ego, ego) | 286 | 3.9 |
| Chain ( ego) | 127 | 1.7 |
| No active structure (dormant + distractor) | 4,867 | 66.8 |
| Total | 7,285 | 100.0 |
| Property | Count | % |
|---|---|---|
| Format | ||
| Binary | 6,072 | 83.3 |
| Multiple choice | 1,213 | 16.7 |
| Difficulty | ||
| Easy | 1,145 | 15.7 |
| Medium | 3,146 | 43.2 |
| Edit operation | Count |
| Node distractor demotion | 1,739 |
| Ego-edge removed | 2,054 |
| Inter-node edge removed | 1,446 |
| Ego-edge added | 527 |
| Ego-edge causal-status string changed | 338 |
| Ego-edge active flag toggled | 327 |
| Decision | Metric | Value |
|---|---|---|
| Causal status (3-class, overall) | 0.81 | |
| Active vs rest | 0.87 | |
| Dormant vs rest | 0.63 | |
| Distractor vs rest | 0.91 | |
| Ego edge effect type (4-class) | 0.85 | |
| Inter-node edge type (4-class) | 0.75 |
| Model | CaI | CA | CB | CoI | BAS | CDE | CR | SC | NC | NDE | NIE | DQ | EL | AB | DR | CI | NI | WC |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Driving-specific VLAs | ||||||||||||||||||
| ImpromptuVLA-7B | 87.5 | 71.4 | 26.9 | 91.5 | 90.9 | 69.4 | 67.6 | 59.0 | 70.9 | 78.3 | 52.0 | 51.4 | 72.4 | 69.8 | 21.7 | 58.6 | 93.0 | 70.1 |
| OpenREAD | 87.9 | 87.8 | 45.6 | 93.2 | 90.9 | 67.7 | 61.7 | 64.7 | 71.4 | 52.2 | 58.0 | 47.9 | 72.9 | 63.2 | 76.3 | 41.0 | 86.6 | 56.7 |
| Orion | 0.0 | 0.0 | 12.1 | 0.0 | 0.0 | 43.6 | 65.1 | 14.7 | 55.9 | 54.4 | 36.0 | 59.9 | 46.3 | 52.4 | 0.0 | 94.1 | 79.9 | 63.0 |
| UniDrive-VLA | 82.4 | 89.8 | 58.4 | 98.3 | 95.5 | 61.3 | 49.4 | 66.5 | 65.7 | 58.7 | 60.0 | 37.1 | 60.6 | 65.8 | 83.5 | 15.4 | 68.0 | 63.2 |
| RecogDrive | 87.6 | 100.0 | 44.0 | 88.7 | 90.5 | 62.7 | 55.2 | 78.1 | 58.6 | 65.9 | 66.7 | 24.1 | 61.7 | 63.2 | 48.4 | 29.1 | 54.7 | 57.8 |
| Model | Active overall | Direct | Chain | Confounding | Collider |
|---|---|---|---|---|---|
| Driving-specialist VLAs | |||||
| RecogDrive | 69.9 | 73.2 | 74.0 | 70.9 | 52.5 |
| OpenREAD | 69.8 | 71.0 | 68.5 | 74.8 | 60.7 |
| ImpromptuVLA-7B | 69.1 | 71.1 | 72.4 | 76.2 | 52.7 |
| UniDrive-VLA | 65.9 | 65.0 | 68.5 | 74.5 | 62.1 |
| SafeAuto | 56.6 | 55.9 | 68.5 | 69.9 | 45.4 |
| Model | Composite | Spatial | Mechanism | Conditionality | Consistency |
|---|---|---|---|---|---|
| Driving-specialist VLAs | |||||
| RecogDrive | 1.25 | 1.36 | 1.40 | 0.75 | 1.48 |
| OpenREAD | 1.18 | 1.14 | 1.30 | 0.83 | 1.44 |
| UniDrive-VLA | 1.12 | 1.21 | 1.24 | 0.74 | 1.31 |
| ImpromptuVLA-7B | 1.06 | 1.08 | 1.12 | 0.63 | 1.39 |
| SimLingo | 0.71 | 0.91 | 0.70 | 0.30 | 0.93 |
| Dimension | Pearson | Spearman |
|---|---|---|
| Composite | 0.97 | 0.92 |
| Spatial grounding | 0.96 | 0.93 |
| Mechanism identification | 0.99 | 0.97 |
| Conditionality awareness | 0.94 | 0.94 |
| Answer consistency | 0.83 | 0.81 |
| Model | CB (Active) | EL (Dormant) | CI (Distractor) | Overall |
|---|---|---|---|---|
| Driving-specialist VLAs | ||||
| ImpromptuVLA-7B | 26.85% | 72.38% | 58.64% | 69.27% |
| OpenREAD | 45.64% | 72.93% | 40.95% | 63.76% |
| Orion | 12.08% | 46.33% | 94.08% | 57.25% |
| UniDrive-VLA | 58.39% | 60.58% | 15.39% | 54.87% |
| RecogDrive | 43.97% | 61.69% | 29.14% | 54.25% |
| Model | Total CTE | GOOD_CF (%) | INCONCLUSIVE (%) | FLAGGED (%) | TRAJ_SAME_BTE (%) |
|---|---|---|---|---|---|
| Driving-specialist VLAs | |||||
| WiseAD | 972 | 48.66 | 33.85 | 17.49 | 17.49 |
| UniDrive-VLA | 1000 | 20.10 | 37.90 | 42.00 | 42.00 |
| Alpamayo-1.5-10B | 1000 | 16.80 | 2.50 | 63.50 | 34.00 |
| ImpromptuVLA-7B | 984 | 15.04 | 45.53 | 42.28 | 22.97 |
| Omnidrive | 999 | 10.71 | 42.64 | 46.65 | 46.65 |
| Model | BTE (m) | CTE-R2 (m) | CTE-R3 (m) | CTE-R2/BTE | CTE-R3/BTE | Regime |
|---|---|---|---|---|---|---|
| Driving-specialist VLAs | ||||||
| WiseAD | 2.91 | 1.97 | 1.57 | 0.68 | 0.54 | C (positive) |
| UniDrive-VLA | 0.68 | 2.90 | 1.96 | 4.26 | 2.88 | B |
| Alpamayo-1.5-10B | 1.31 | 2.70 | 1.70 | 2.06 | 1.30 | B+C |
| ImpromptuVLA-7B | 1.27 | 5.69 | 2.97 | 4.48 | 2.34 | B |
| Omnidrive | 5.39 | 4.51 | 2.48 | 0.84 | 0.46 | C |
| Model | Language backbone | Source |
| Driving-specific VLAs | ||
| ImpromptuVLA-7B | Qwen2.5-VL-7B | [ 11 ] §2 |
| OpenREAD | Qwen3-VL-8B ∗ | [ 43 ] §3.1 |
| UniDrive-VLA | Qwen3-VL-8B ∗ | [ 24 ] Tab. 3 |
| RecogDrive | InternVL3-8B ∗ | [ 23 ] App. E |
| Alpamayo-1.5-10B | Cosmos-Reason ∗ | [ 36 ] §3.1 |
| Backbone | Vanilla VLM (%) | Driving VLA | Driving VLA (%) | (pp) |
|---|---|---|---|---|
| Qwen3-VL-8B | 66.04 | OpenREAD | 63.76 | |
| Qwen3-VL-8B | 66.04 | UniDrive-VLA | 54.87 | |
| InternVL3-8B | 62.91 | RecogDrive | 54.25 | |
| Cosmos-Reason | 70.56 | Alpamayo-1.5-10B | 36.86 |
| Model | RFT reward composition | Policy updated | QA (pp) |
|---|---|---|---|
| Alpamayo-1.5-10B | Reasoning quality + reasoning–action consistency + trajectory L2/collision/jerk | Whole VLA (GRPO) | |
| RecogDrive | NAVSIM PDMS (collisions, drivable area, comfort) only | Diffusion planner only (DiffGRPO; VLM frozen) | |
| OpenREAD | LLM-as-critic on QA semantic match + embedding similarity + trajectory ADE | Whole VLA (GRPO) |
| Inputs | Driving VLAs | General-purpose VLMs | ||||
|---|---|---|---|---|---|---|
| OpenREAD | AlpaMayo-1.5 | Qwen3-VL-8B-Thinking | Cosmos-Reason2-8B | |||
| Reasoning on with injected : spread of across counterfactual rationales | ||||||
| ✓ | ✓ | ✓ | No effect | No effect | No effect | No effect |
| ✓ | ✗ | ✓ | No effect | No effect | No effect | No effect |
| ✗ | ✓ | ✓ | Some effect | No effect | Hallucinates | Hallucinates |
| ✗ | ✗ | ✓ | Good effect | No effect | Hallucinates | Hallucinates |
| Model | ER | ER | ER | ER | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cosmos-Reason-2 (VLM) | — | — | — | — | ||||||||
| Alpamayo-1.5-10B (VLA) | ||||||||||||
| Qwen3-VL-8B (VLM) | — | — | — | — | ||||||||
| OpenREAD (VLA) | ||||||||||||