This was a script I found on my Github from 3 years ago. Feel free to use as you’d like, please take a look at the Github readme 
I do not plan to provide support for this resource - it’s pretty self explanatory. Use at your discretion. May not work with every emergency vehicle.
Is it supposed to replace ELS?
Cool release! Might update n PR!
Nope, not a replacement for ELS unless it fits your needs. This is simply a method to control the light pattern individually by using the numpad keys (or whatever keys you set it to).
Understood. Thank you!
im confused is this only useable IF one has ELS in fiveM or is it a replacement for ELS (ie NON-ELS vehicles)
This was originally created for a vehicle with a very specific lighting pattern created by @TheKodah. Therefore, you’d need to modify the vehicle to ensure the lighting pattern matches up or alter both.
You can see the use of it just above the map. @hallux made this script so that it could be more realistic and so that you can switch between lights faster. This is still a NON-ELS vehicle, not ELS.