Freeway#

../../../_images/freeway.gif

This environment is part of the Atari environments. Please read that page first for general information.

Action Space

Discrete(3)

Observation Shape

(210, 160, 3)

Observation High

255

Observation Low

0

Import

gymnasium.make("ALE/Freeway-v5")

For more Freeway variants with different observation and action spaces, see the variants section.

Description#

your objective is to guide your chicken across lane after lane of busy rush hour traffic. You receive a point for every chicken that makes it to the top of the screen after crossing all the lanes of traffic.

For a more detailed documentation, see the AtariAge page

Actions#

Freeway has the action space Discrete(3) with the table below lists the meaning of each action’s meanings. As Freeway uses a reduced set of actions for v0, v4 and v5 versions of the environment. To enable all 18 possible actions that can be performed on an Atari 2600, specify full_action_space=True during initialization or by passing full_action_space=True to gymnasium.make.

Value

Meaning

Value

Meaning

Value

Meaning

0

NOOP

1

UP

2

DOWN

Observations#

Atari environment have two possible observation types, the observation space is listed below. See variants section for the type of observation used by each environment id.

  • obs_type="rgb" -> observation_space=Box(0, 255, (210, 160, 3), np.uint8)

  • obs_type="ram" -> observation_space=Box(0, 255, (128,), np.uint8)

Additionally, obs_type="grayscale" cause the environment return a grayscale version of the rgb array for observations with the observation space being Box(0, 255, (210, 160), np.uint8)

Rewards#

The exact reward dynamics depend on the environment and are usually documented in the game’s manual. You can find these manuals on AtariAge.

Atari environments are simulated via the Arcade Learning Environment (ALE) [1].

Variants#

Freeway has the following variants of the environment id which have the following differences in observation, the number of frame-skips and the repeat action probability.

Env-id

obs_type=

frameskip=

repeat_action_probability=

Freeway-v0

"rgb"

(2, 5)

0.25

Freeway-ram-v0

"ram"

(2, 5)

0.25

Freeway-ramDeterministic-v0

"ram"

4

0.25

Freeway-ramNoFrameskip-v0

"ram"

1

0.25

FreewayDeterministic-v0

"rgb"

4

0.25

FreewayNoFrameskip-v0

"rgb"

1

0.25

Freeway-v4

"rgb"

(2, 5)

0.0

Freeway-ram-v4

"ram"

(2, 5)

0.0

Freeway-ramDeterministic-v4

"ram"

4

0.0

Freeway-ramNoFrameskip-v4

"ram"

1

0.0

FreewayDeterministic-v4

"rgb"

4

0.0

FreewayNoFrameskip-v4

"rgb"

1

0.0

ALE/Freeway-v5

"rgb"

4

0.25

ALE/Freeway-ram-v5

"ram"

4

0.25

Difficulty and modes#

It is possible to specify various flavors of the environment via the keyword arguments difficulty and mode. A flavor is a combination of a game mode and a difficulty setting. The table below lists the possible difficulty and mode values along with the default values.

Available Modes

Default Mode

Available Difficulties

Default Difficulty

[0, ..., 7]

0

[0, 1]

0

Version History#

A thorough discussion of the intricate differences between the versions and configurations can be found in the general article on Atari environments.

  • v5: Stickiness was added back and stochastic frameskipping was removed. The environments are now in the “ALE” namespace.

  • v4: Stickiness of actions was removed

  • v0: Initial versions release