Taxi

State and action spaces

The 500 states encode taxi row \(r\), column \(c\), passenger index \(p\in{R,G,Y,B,\text{taxi}}\), and destination \(d\in{R,G,Y,B}\):

\[ s=4\left(5(5r+c)+p\right)+d. \]

Actions are 0 = south, 1 = north, 2 = east, 3 = west, 4 = pickup, and 5 = dropoff. Grid boundaries and the fixed interior walls block movement.

Dynamics and reward

Movement and a legal pickup reward \(-1\). Illegal pickup/dropoff rewards \(-10\). Dropping the carried passenger at the destination rewards \(+20\) and terminates. Dropping at another named location leaves the passenger there with the ordinary \(-1\) reward.

Reset samples taxi position, destination, and a distinct waiting location from a seeded RNG.

Episode end

Successful delivery terminates. Reaching max_episode_steps truncates and may coincide with delivery.

Configuration

Info is (). Reference: Gymnasium Taxi.