So i was just thinking about if it possible to add more cop cars then "police3" and "police4" to the Added car spawning menu? If that is possible how does that work? Thank you

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I actually think it is possible, you would just have to edit numerous files such as vehicles.dat and handling.dat and a WHOLE LOT MORE! It would take a long time, though.

Actually, no. It is very easy as long as you know what you are doing. Lets say i wanted to add this 

i would open up, cargrp and add police3 right after fib, next, i would open, carcols and add police3 with the colors of police or police2, then, i would open handling, and find the FIB car handling, copy it, and paste it below police2 and rename it to police3, after that, i'd open vehoff and find, fib, copy all of it's lines, replace anything in those lines that i copied that says fib, to police3 and paste it under the last line of police2, and lastly, i would open vehicles.dat and copy the fib buffalo's line, and rename the first 3 fib lines into police3, and the last line that says fib, i would leave alone. That's how you add the car. It seems like a lot of work, but it really only takes about 3 minutes. Oh, and spawning it into IV won't work unless you open it with the console and type, "spawn police3". (Without the ")

However: The only vehicles that can have working lights and sirens are police, police2, police3, police4, policeb, nstockade, pstockade, noose, polpatriot, fbi, firetruk, and ambulance. It is not possible to add to this list. All of these are by default already in BOGT, so no added cars can have working sirens in BOGT; in IV, the only added cars that can have working sirens are police3, police4, policeb. ELS works on any car slot present by default in IV or EFLC (both TLAD and BOGT), so adding cars with the same name as an EFLC slot to IV lets ELS work (although it cannot make AI cars pull over). ELS also works on emerg1 through emerg7. It does not work on any other car slots (e.g. if you add police5, ELS will not work with that slot).

However: The only vehicles that can have working lights and sirens are police, police2, police3, police4, policeb, nstockade, pstockade, noose, polpatriot, fbi, firetruk, and ambulance. It is not possible to add to this list. All of these are by default already in BOGT, so no added cars can have working sirens in BOGT; in IV, the only added cars that can have working sirens are police3, police4, policeb. ELS works on any car slot present by default in IV or EFLC (both TLAD and BOGT), so adding cars with the same name as an EFLC slot to IV lets ELS work (although it cannot make AI cars pull over). ELS also works on emerg1 through emerg7. It does not work on any other car slots (e.g. if you add police5, ELS will not work with that slot).

Alright, thank you for your asnwer cp702! that answered my question.