Aviation authorities became concerned about designing TCAS since late 1950-s. As aviation transport grew in size, volume and speed, mid-air collisions became a serious threat, which started to kill people and it needed to get stopped. First generation of TCAS was ready by the end of the 1990-s and it was installed on most commercial aircraft.
TCAS
English aviation topic about TCAS: why collision avoidance systems appeared, how they reduce mid-air collision risk and what terminology is used.