From Carmageddon Wiki

This is a mode currently available for Carmageddon: Reincarnation. CarMODgeddon currently has support for level, vehicle and wheel mods. To put your mods in Carmageddon: Reincarnation you'll need to create a folder called "CarMODgeddon" within your game folder. Inside this you'll also need to create the following folders:

  • Levels
  • Vehicles
  • Wheels

Mods are then individually enabled by inclusion in the “CarMODgeddon.lua” file (you will need to create this) in the base of the CarMODgeddon folder. The contents of the CarMODgeddon.lua file take the following form:

carmodgeddon = {
	level_mods = {
		{ base_name = "level_mod_1" },
		{ base_name = "C1City_C" },
	vehicle_mods = {
		{ base_name = "my_new_car" },
	wheel_mods = {
		{ base_name = "Wheels4mecar" },

Levels, all cars that aren’t DLC, and all rims/skins are unlocked whilst in CarMODgeddon mode. Career, save games, stats, leaderboards are all disabled.