peterwolf's Splinecart

Splinecart adds track ties that a player places in mid-air to shape a curved route. Placing a tie automatically aligns it with the look direction, and an empty-hand click rotates it. Two ties are joined with a Track item to form a smooth path, and the curves are smoothed so a minecart travels without jerking and with banking speed physics. Minecarts move between Splinecart tracks and vanilla rails without losing momentum.

The mod covers both ordinary and specialised track. Regular ties act as detector rails and send a 15 redstone signal whenever a minecart crosses them. Ties of the steel kind come with a third powered rail and support pillars, and wooden ties add wooden beams and posts. Chain Drive Track pulls a minecart at constant speed up hills, which suits roller coasters, and Magnetic Track accelerates a cart when powered and brakes it when unpowered, even on steep slopes. Turnouts switch a minecart between two exits: a tie becomes a redstone-controlled switch, and a minecart follows the main track when the state is 0 and turns onto the second exit when it is powered.

Installation needs Fabric or NeoForge with the matching build for the game version. Splinecart runs on client and server, so the server and every player need it. Files cover 1.21.11 – 26.3 in four release versions, and the mod is released under the Mozilla Public License 2.0, so it is not open source.