Bus engine: Bus Engine Idling by bikesnbassboi, CC0.
Tuk-tuk engine: Auto Rickshaw – Engine Cabinet (Back) Sounds.wav by kalhan / FVC students, NID Sound Design workshop, CC BY 4.0. Recorded from a Bajaj auto-rickshaw.
Both recordings were cropped, filtered, normalized and crossfaded. Playback pitch changes with engine RPM. Bus air-brake release is synthesized.
Full asset credits are included in CREDITS.md beside the game launcher.