Release Notes¶

v1.12: Vehicle behaviour fix, generic merge env, Gymnasium-compliant render behaviour, and docs refresh¶

Released on 2026-07-06 - GitHub - PyPI

HighwayEnv v1.12.0

This is a big release that brings:

a new generic version of the merge environment
major documentation updates
reduction in startup latency
improvements in dependency situation (replacing pygame with pygame-ce, removing scipy)
multiple new environment versions due to a bug discovered in neighbouring vehicle detection in environments with multiple road segments (causing non-player vehicles to have a higher likelihood of crashing than they should, as shown here).

Minor breaking change

Previously, HighwayEnv did not implement render mode according to Gymnasium; instead, whether the environments are actually rendered is set with the offscreen_rendering config key. #700 introduced correct behaviour for treating different values of render_mode, while still keeping old config keys as overrides:

render_mode="human" -> render to window by default, render() returns None
render_mode="rgb_array" -> headless render by default, render() returns image array
Keeping offscreen_rendering in config as an override
The OFFSCREEN_RENDERING environment variable is now ignored because explicit is better than implicit

So, basically, you can set render_mode="rgb_array" and pass offscreen_rendering=True in the config dict to get both an RGB array returned by render() and pygame rendering in a new window for your viewing pleasure (note that you still need real_time_rendering=True to render at the intended fps).

New environment variant

Generic version of the merge environment (merge-generic-v0, merge-generic-v1) by @Minipoloalex (#694)

New environment version

With neighbour vehicle detection fix: exit-v1, intersection-v2, intersection-multi-agent-v2, merge-v1, racetrack-v1, racetrack-large-v1, racetrack-oval-v1, roundabout-v1, oundabout-generic-v1, u-turn-v1 by @Lidang-Jiang (#667)

Bug fix

Fix neighbour_vehicles not detecting vehicles on connected lanes by @Lidang-Jiang (#667)
Ensure compliance with Gymnasium's definition of render_mode by @Trenza1ore (#700)
Minor typing and NumPy 2.x compatibility fixes by @Trenza1ore (#698, #705)
Call super in LinearVehicle.randomize_behavior by @m-walters (#614)

Dependencies

Replaced pygame with pygame-ce by @Trenza1ore (#678)
Removed dependency on scipy by @Trenza1ore (#691)

Performance

Reduced startup latency by initializing only the needed pygame modules by @Trenza1ore (#687)

Documentation

Docs added for 4 existing environments (exit, lane_keeping, two_way, u_turn) by @Trenza1ore (#697)
Docs added for rendering modes and configurations by @Trenza1ore (#700)
Docs added for neighbour vehicle detection issue by @Trenza1ore & @Lidang-Jiang (#667)
Release notes section by @Trenza1ore (#706)
Update outdated sections in docs by @Trenza1ore (#699)
Fixed warnings in documentation build process by @Luzijano & @Trenza1ore (#690, #695)

Community

Readme rewritten for compactness by @kydrahul & @Trenza1ore (#682)
Contributing guideline written by @kydrahul & @Trenza1ore (#702)
Issue & pull request templates by @Trenza1ore (#679)
Unit test coverage requirements for pull requests by @Trenza1ore (#705, #707)

CI and build

General CI improvements by @mwydmuch & @Trenza1ore (#680, #681, #683)

New Contributors

@Trenza1ore made their first contribution in #678
@mwydmuch made their first contribution in #680
@kydrahul made their first contribution in #682
@Luzijano made their first contribution in #690

Full Changelog: v1.11...v1.12

v1.11: Python 3.14 support, new env variant, and stability updates¶

Released on 2026-05-10 - GitHub - PyPI

Changes since `v1.10.2`

Compatibility

Added Python 3.14 support.
Dropped Python 3.9 support.
Fixed NumPy 2.0 compatibility.
Modernized build configuration.

CI and build tooling

Added CI/install support for pygame system dependencies.
Installed SDL2/freetype/portmidi packages for docs/build environment.

Bug fixes

Fixed SubprocVecEnv ConnectionResetError with forkserver/spawn.
Fixed zero division in LinearSpline2D.
Fixed divide-by-zero warning in LidarObservation.
Fixed incorrect coordinate transformation in spline.

Features and docs

Added a generic version of the roundabout environment.
Refreshed docs branding and added mise/just tooling.
Updated docs workflows and README content.
Added multiple paper citations / references.

v1.10.2: Bug fixes and new env¶

Released on 2025-10-18 - GitHub - PyPI

Adds racetrack-oval-v0
Minor fixes

v1.10.1: Gymasium v1.0 support¶

Released on 2024-08-19 - GitHub - PyPI

Fix release workflow

v1.10: Gymnasium v1.0 support¶

Released on 2024-08-18 - GitHub - PyPI

Update to support Gymnasium v1.0

v1.9.1: Update release version¶

Released on 2024-08-11 - GitHub - PyPI

(Didn't see that the version definition had been moved from config to init)

v1.9: Bug fixes¶

Released on 2024-08-11 - GitHub - PyPI

Fix creation of vehicles in parking env
Bug fixes for kinematics observation
Fix Lidar observation
Fix boundaries check in occupancy grid observation
Update docs
Update numpy deprecated calls
Fix road priorities
Fix non-determinism in route planning
Fix multiagent wrapper for intersection env

v1.8.2: Hotfix of parking env reward function¶

Released on 2023-05-30 - GitHub - PyPI

Fix collision reward in parking env
Minor update of documentation and workflows
Minor update of example notebooks
Update rendering logic

v1.8.1: Hotfix of env registration entrypoint with gymnasium¶

Released on 2023-03-22 - GitHub - PyPI

v1.8: Move from gym to gymnasium¶

Released on 2023-03-18 - GitHub - PyPI

fix vehicle order in occupancy grid obs
fix broken seeding implementation
support numpy types for discrete actions
use Runge-Kutta 4 integration for dynamical continuous actions, making the dynamics make more stable
use gymnasium rather than gym

v1.7.1: Hotfix of parking env init¶

Released on 2022-12-19 - GitHub - PyPI

Fixes #400

v1.7: Add support for gym 0.26¶

Released on 2022-11-06 - GitHub - PyPI

Change the step / reset / render interfaces to match the new API of gym 0.26
Drop support for gym <0.26

v1.6: Environment variants with continuous actions and multi-objective, bug fixes.¶

Released on 2022-08-14 - GitHub - PyPI

fix a bug in generating discrete actions from continuous actions
fix more bugs related to changes in gym's latest versions
new intersection-env variant with continuous actions
add longitudinal/lateral/angular offsets to the lane as part of the kinematics observation's features
add more configurable options for reward function and termination conditions
add configurable min/max speed for continuous actions
bug fix for reward computation in the multi-agent setting
add get_available_actions for MultiAgentAction
fix various deprecation warnings
add a multi-objective version of HighwayEnv

Huge thanks to contributors @zerongxi, @TibiGG, @KexianShen, @lorandcheng

v1.5: New observation types and lane geometries, and bug fixes¶

Released on 2022-03-19 - GitHub - PyPI

Add documentation on continuous actions
Fix various bugs or imprecision in collision checks and obstacles rendering
Image observations are now centered on the observer vehicle
Fix the lane change behaviour in some situations
Add TupleObservation, which is a union of several observation types
Improve the accuracy of the LidarObservation
Add support for PolyLane, and methods to save/load road networks from a config
Fix steering wheel / angle conversion
Change of the velocity term projection in the reward function
Add support for latest gym versions (>=0.22) which dropped the Monitor wrapper
Add a copy of the GoalEnv interface which was removed from gym

v1.4: New continuous control environment: racetrack-v0¶

Released on 2021-09-21 - GitHub - PyPI

This release introduces additional content:

a new continuous control environment, racetrack-v0, where the agent must learn to steer and follow the tracks, while avoiding other vehicles
a new "on_road" layer in the OccupancyGrid observation type, which enables the observer to see the drivable space
a new "align_to_vehicle_axes" option in the OccupancyGrid observation type, which renders the observation in the local vehicle frame
a new DiscreteAction action type, which discretizes the original ContinuousAction type. This allows to do low-level control, but with a small discrete action space (e.g. for DQN). Note that this is different from the DiscreteMetaAction type, which implements its own low-level sub-policies.
new example scripts and notebooks for training agents, such as a PPO continuous control policy for racetrack-v0.
updated documentation

v1.3: Faster variant of highway-v0, and bug fixes¶

Released on 2021-08-30 - GitHub - PyPI

This release contains

A few fixes for compatibility with SB3
Some changes for video rendering and framerate
highway-fast-v0: a faster variant of highway-v0 to train/debug models more quickly

v1.2: Compatibility with stable-baselines3¶

Released on 2021-04-29 - GitHub - PyPI

Minor update with

different handling of image observations + example script with stable baselines
small changes in the dynamical model

v1.1: First PyPI release¶

Released on 2021-03-12 - GitHub - PyPI

Main changes:

vehicles appearance
exit environment
u-turn environment
lidar observation
big fix in video recording

v1.0: First stable release¶

Released on 2020-09-07 - GitHub - PyPI