You need the ELS modification. Without it, the emergency lights will not work
Model name: policet
This mod replaces the police van with a Dutch Volkswagen T4 police vehicle.
changelog:
Version 1.1:
Fixed file name which may fix certain texture bugs.
Installation instructions:
> Go to mods/update/x64/dlcpacks/patchday21ng (Latest patchday)/dlc.rpf/x64/levels/gta5/vehicles/rpf
> Drag the .ytd and .yft files in here
> Go to the game’s main folder and ELS/pack default
> Drag policet.xml in here
Features:
Working siren.
Animated doors.
Gunshot impacts
Known bugs:
Headlights and rear lights do not work.
Glass can’t breaks.
Rear passenger door clips through the vehicle when opened.
Credits:
Original SA mod: gta4-gtasa
Converted to gta V: GloriusModding (Luuk)
Template: GloriusModding (Justin)
Whelen L31 model: tomcat8492
Converted to GTA V: MisterDarkSide
Striping: SizzGamesMods – Iddo