YFD, Who/What is Car 5 & 6

[Steve 78]

Who/What is Car 5 & 6 in Yonkers FD?

[R1SmokeEater 359]

Car-5 is Safety, Car-6 is FIU (Fire Investigation)

[spyda308 11]

car 5 is out of hq, car 6 is out of 7engine.

[SQDBOSS 6]

I've noticed on YFD posts that that they appear to be filling out first assignments. Is the safety an additional chief? and why roll a fire investigator on all possible jobs? Does he/she serve an additonal function to the assignment?