- For other uses of "cloverleaf", see Cloverleaf (disambiguation).
Cloverleaf interchange (or fourfold racetrack-weld-racetrack) is a 56-cell still life exhibiting D8_1 symmetry.
While known for many years beforehand due to its ability to be hassled, it is notable due to a natural occurrence being found in the ash of a random asymmetric soup by Adam P. Goucher on August 12, 2016. This made it the single largest known still life to occur completely naturally, surpassing the previous record holder, the 46-cell professor; it had previously arisen semi-naturally in various higher symmetries, including C2_1, C4_1, D2_+1, D4_+1, D4_+2 and D4_x1. It has since been tied in C1 by another, unnamed 56-cell still life found by John Goodman in September 2021.
BlinkerSpawn found a 12-glider synthesis on the same day. GUYTU6J improved this to 10 gliders on February 5, 2020.
A cloverleaf interchange can be hassled by Carnival shuttles, like this: