In Submission for Sensors 2026

A Curriculum Approach to Bridge the Reality Gap in Autonomous Driving Decision-Making based on Deep Reinforcement Learning

1Universidad de Alcalá
Curriculum Approach Architecture

Abstract

Decision-Making is a fundamental topic in the domain of Autonomous Driving where significant challenges must be tackled due to the variable behaviours of surrounding agents and the wide array of encountered scenarios. The primary aim of this work is to develop a hybrid Decision-Making architecture able to be validated on a real vehicle that marries the reliability of classical techniques with the adaptability of Deep Reinforcement Learning approaches. To address the crucial transition from simulated training environments to real-world applications, this research employs a Curriculum Learning approach, facilitated by the deployment of Digital Twins and Parallel Intelligence technologies, significantly narrowing the Reality Gap and enhancing the applicability of learned behaviours. The viability of this approach is evidenced through a Parallel Execution, wherein simulated and real-world tests are conducted simultaneously. Specifically, our approach consistently surpasses the performance benchmarks set by existing frameworks in the literature within SMARTS, achieving success rates over 91%. Additionally, it completes various scenarios in CARLA up to 50% faster than the Autopilot, demonstrating improved comfort and safety.

Experiments in SUMO

Lightweight simulation for high-level behaviours learning.

Unprotected Left Turn Scenario

The green agent must merge into the left lane.

Left Turn SUMO

Three Lane Merge Scenario

The green agent must merge into the traffic.

Merge SUMO

Three Lane Road Scenario

The green agent must reach the end of the road.

Lane Change SUMO

Roundabout Scenario

The green agent must merge into the roundabout and leave it in the last exit.

Roundabout SUMO

SUMO Quantitative Results

The results in terms of success rate (%) and average completion time (sec). An ablation study between different DRL agents and a comparison to representative SOTA proposals are presented. The training progression of the rewards is also represented.

SUMO Results

Experiments in CARLA

Realistic simulation including vehicle dynamics.

Town 03 Crossroad Scenario

The ego vehicle must cross the intersection while vehicles are coming from both sides.

Crossroad CARLA

The ego vehicle stops due to the adversarial vehicles and starts moving when it identifies a gap. The control signals and comfort metrics are represented below.

Crossroad Control

Town 03 Merge Scenario

The ego vehicle must merge into the right lane while vehicles are coming from the left side.

Merge CARLA

The ego vehicle stops due to the adversarial vehicles and starts moving when it identifies a gap. The control signals and comfort metrics are represented below.

Merge Control

Town 04 Lane Change Scenario

The ego vehicle must drive until the end of the road while vehicles are driving in this road.

Lane Change CARLA

The ego vehicle changes lane two times resulting in the shown control signals.

Lane Change Control

Town 03 Roundabout Scenario

The ego vehicle must merge into the roundabout and leave it in the second exit.

Roundabout CARLA

The control signals are represented for the vehicle approaching and merging into the roundabout.

Roundabout Control

Town 03 Concatenated Scenario

The ego vehicle drives through all the previously introduced scenarios in a concatenated way.

Concatenated CARLA

The first chart shows the ego vehicle performance while the second one presents the CARLA Autopilot signals under the same scenario.

Concatenated Control 1 Concatenated Control 2

CARLA Quantitative Results

The comparison using different metrics between our proposal and the CARLA Autopilot.

CARLA Results

Parallel Execution Experiments

Validation of our proposal with a Parallel Execution in a merge scenario in our University Campus using our Real Vehicle.

Low Traffic Flow

Front View

Low Traffic Front View

Side View

Low Traffic Side View

Control Graphics

Low Traffic Control

Mixed Traffic Flow

Front View

Mixed Traffic Front View

Side View

Mixed Traffic Side View

Control Graphics

Mixed Traffic Control

BibTeX

@article{gutierrez2024curricular,
  author    = {Gutiérrez-Moreno, Rodrigo and Barea, Rafael and López-Guillén, Elena and Arango, Felipe and Sánchez-García, Fabio and Bergasa, Luis Miguel},
  title     = {A Curriculum Approach to Bridge the Reality Gap in Autonomous Driving Decision-Making based on Deep Reinforcement Learning},
  journal   = {Sensors},
  year      = {2026},
}