A very simple plugin for Alexander Blade's ScriptHookV wizardry that lets you toggle the turn signals on applicable vehicles.
To toggle the left turn signal, press the J key. To toggle the right turn signal, press the K key. You can have both signals on simultaneously. Which you should do if you stop or slow down suddenly. Safety first!
It kinda bothered me that I couldn't play around with the turn signals.
Move TurnSignals.asi to the main GTAV folder (the one with GTA5.exe).
Remove TurnSignals.asi from the main GTAV folder (the one with GTA5.exe).