Adds GUI panel with colored buttons to toggle acceleration and brakes, so that you don't have to hold W or S.
Hotkeys are Ctrl+W / Ctrl+S by default, configurable under Options -> Controls -> Mods tab.
Cruise/Brake states are mutually exclusive (enabling one disables the other), and only get auto-disabled upon leaving the vehicle.
Most useful when driving tanks or trains on slower game speed, allowing to freely check map and manage stuff there without dropping metaphorical foot from the gas pedal.
Some other mods like Pavement Drive Assist and FARL also include such functionality, but this one doesn't bring all the other stuff they do with it, and does not limit its use in any way (required tech, items, trains-only, etc).