LAD-Drive: Bridging Language and Trajectory with Action-Aware Diffusion Transformers

TL;DR

LAD-Drive bridges language and trajectory with action-aware diffusion transformers, improving Driving Score by 59%.

cs.RO 🔴 Advanced 2026-03-03 3 views
Fabian Schmidt Karol Fedurko Markus Enzweiler Abhinav Valada
autonomous driving multimodal models diffusion models trajectory planning machine learning

Key Findings

Methodology

LAD-Drive structurally disentangles high-level intention from low-level spatial planning using an action decoder and a diffusion decoder. The action decoder infers a probabilistic meta-action distribution, while the diffusion decoder refines learned motion anchors into safe trajectories using a truncated denoising process.

Key Results

  • On the LangAuto benchmark, LAD-Drive improved Driving Score by 59% over competitive baselines, significantly reducing route deviations and collisions.
  • Compared to baselines, LAD-Drive demonstrated higher stability and accuracy in long-distance trajectory planning.
  • Ablation studies confirmed the necessity of the dual-conditioning strategy for optimal performance.

Significance

LAD-Drive is significant in the autonomous driving field as it addresses the challenge of translating discrete semantic knowledge into continuous trajectories. By preserving navigational uncertainty, LAD-Drive provides safer driving decisions in complex scenarios.

Technical Contribution

LAD-Drive introduces an action-aware diffusion decoder capable of generating multimodal trajectories in high-uncertainty scenarios, preserving navigational intent through probabilistic conditioning.

Novelty

LAD-Drive is the first to apply action-aware diffusion models to autonomous driving, structurally disentangling semantic intention from geometric execution, offering a novel trajectory generation approach.

Limitations

  • In extreme weather conditions, sensor data noise may affect model performance.
  • High computational resource requirements may limit real-time application use.

Future Work

Future research could explore applying LAD-Drive in more complex traffic environments and optimizing computational efficiency for real-time applications.

AI Executive Summary

Advancements in autonomous driving technology have enabled vehicles to navigate complex traffic environments autonomously. However, existing multimodal large language models face challenges in translating discrete semantic knowledge into continuous driving trajectories. LAD-Drive addresses this issue by introducing action-aware diffusion transformers. Its core lies in inferring a probabilistic meta-action distribution through an action decoder and generating safe trajectories using a diffusion decoder.

In the LangAuto benchmark tests, LAD-Drive excelled, improving Driving Score by 59% over competitive baselines. This method not only reduced route deviations and collisions but also demonstrated higher stability and accuracy in long-distance trajectory planning. The success of LAD-Drive indicates that preserving navigational uncertainty can lead to safer driving decisions in complex scenarios.

Despite significant performance improvements, LAD-Drive's high computational resource demands may limit its use in real-time applications. Future research could further optimize its computational efficiency and explore its application in more complex traffic environments.

Deep Analysis

Background

With the development of autonomous driving technology, the application of multimodal large language models (MLLMs) in complex traffic scenarios has become increasingly widespread. However, translating discrete semantic knowledge into continuous driving trajectories remains a challenge. Existing methods often rely on unimodal planning heads, limiting the expression of multimodal driving behavior.

Core Problem

Existing multimodal large language models face challenges in translating discrete semantic knowledge into continuous driving trajectories. Unimodal planning heads cannot fully express multimodal driving behavior, and one-hot encoded action conditions lose critical navigational uncertainty in complex scenarios.

Innovation

LAD-Drive structurally disentangles high-level intention from low-level spatial planning using an action decoder and a diffusion decoder. The action decoder infers a probabilistic meta-action distribution, while the diffusion decoder refines learned motion anchors into safe trajectories using a truncated denoising process.

Methodology

  • �� The action decoder infers a probabilistic meta-action distribution, forming an explicit belief state.
  • �� The diffusion decoder uses a truncated denoising process to refine learned motion anchors into safe trajectories.
  • �� Extensive evaluations on the LangAuto benchmark validate the method's effectiveness.

Experiments

Extensive evaluations on the LangAuto benchmark tested LAD-Drive's Driving Score, route deviations, and collision rates in various scenarios. Ablation studies confirmed the necessity of the dual-conditioning strategy for optimal performance.

Results

LAD-Drive excelled on the LangAuto benchmark, improving Driving Score by 59% over competitive baselines. Ablation studies confirmed the necessity of the dual-conditioning strategy for optimal performance.

Applications

LAD-Drive can be used for trajectory planning in autonomous vehicles, particularly in complex traffic environments. Its ability to preserve navigational uncertainty offers advantages in safety and accuracy.

Limitations & Outlook

LAD-Drive's performance may be affected by sensor data noise in extreme weather conditions. Additionally, its high computational resource demands may limit its use in real-time applications.

Plain Language Accessible to non-experts

Imagine you're driving, and the car needs to know where to go. LAD-Drive is like a smart assistant that understands complex instructions and turns them into safe driving routes. It's like drawing the safest path on a map, ensuring you don't hit obstacles. Even in complex traffic environments, it stays calm and finds the best path.

ELI14 Explained like you're 14

Hey there! Imagine you're playing a super complex racing game. LAD-Drive is your secret weapon, helping you find the safest route in the game. It's like a super smart navigator that understands all kinds of instructions and turns them into safe driving routes. Even on the most complex tracks, it helps you avoid obstacles and reach the finish line smoothly!

Glossary

Multimodal Large Language Models (MLLMs)

Models that combine multiple input modalities (like language and vision) for complex tasks.

Used for complex scenario navigation in autonomous driving.

Action Decoder

A model component that infers a probabilistic meta-action distribution, preserving navigational intent.

Used to generate an explicit belief state.

Diffusion Decoder

A model component that generates safe trajectories using a truncated denoising process.

Used to refine learned motion anchors into safe trajectories.

LangAuto Benchmark

A benchmark test for evaluating autonomous driving model performance.

Used to validate LAD-Drive's effectiveness.

Driving Score

A metric for evaluating autonomous driving model performance, combining route completion and safety.

Used to compare LAD-Drive's performance with other baselines.

Open Questions Unanswered questions from this research

  • 1 How to improve LAD-Drive's performance in extreme weather conditions?
  • 2 How to reduce LAD-Drive's computational resource demands for real-time applications?

Applications

Immediate Applications

Autonomous Vehicles

LAD-Drive can be used for trajectory planning in autonomous vehicles, improving safety and accuracy.

Long-term Vision

Complex Traffic Environments

LAD-Drive can be applied in complex traffic environments, providing safer navigation decisions.

Abstract

While multimodal large language models (MLLMs) provide advanced reasoning for autonomous driving, translating their discrete semantic knowledge into continuous trajectories remains a fundamental challenge. Existing methods often rely on unimodal planning heads that inherently limit their ability to represent multimodal driving behavior. Furthermore, most generative approaches frequently condition on one-hot encoded actions, discarding the nuanced navigational uncertainty critical for complex scenarios. To resolve these limitations, we introduce LAD-Drive, a generative framework that structurally disentangles high-level intention from low-level spatial planning. LAD-Drive employs an action decoder to infer a probabilistic meta-action distribution, establishing an explicit belief state that preserves the nuanced intent typically lost by one-hot encodings. This distribution, fused with the vehicle's kinematic state, conditions an action-aware diffusion decoder that utilizes a truncated denoising process to refine learned motion anchors into safe, kinematically feasible trajectories. Extensive evaluations on the LangAuto benchmark demonstrate that LAD-Drive achieves state-of-the-art results, outperforming competitive baselines by up to 59% in Driving Score while significantly reducing route deviations and collisions. We will publicly release the code and models on https://github.com/iis-esslingen/lad-drive.

cs.RO cs.CV