Sources

-- Light Reflector Handler
-- handler.client.luau (continued)

-- Assuming this is an A-Chassis vehicle
local function determineIntensity(vehicle: Model)
    -- This is just an example and every headlight system will be different.
    local values = vehicle.DriveSeat:FindFirstChild("Values")
    local intensity = 1

    -- If the high beams are enabled, then the intensity will be greater.
    if values and values.HighBeam.Value == true then
        intensity = 1.5
    end

    -- continue on....

    return intensity
end

local function determineColor(vehicle: Model): vector
    local color: Color3?

    if vehicle.Model == "Car1" then
        color = Color3.fromRGB(211, 194, 151)
    end

    -- continue on....

    if not color then
        color = Color3.fromRGB(255, 255, 255)
    end 
    
    return vector.create(color.R, color.G, color.B)
end

-- Assuming this is an A-Chassis vehicle
local function CheckForRegLightValue(vehicle: Model)
    -- This is just an example and every headlight system will be different.
    local values = vehicle.DriveSeat:FindFirstChild("Values")

    -- Just check if there is a headlight value
    if values and values:FindFirstChild("LowBeam") then
        return values.LowBeam
    end

    -- continue on....

    -- Use `true` as a fallback if you cannot return any values. 
    -- Note that this will enable the source for the respective vehicle regardless if the headlights are on or not.
    return true
end

local function isAVehicle(model: Model)

    -- First check if the model is actually a model
    if not model:IsA("Model") then
        -- Not a model, so not a vehicle either!
        return false
    end     

    -- Add a variable to avoid repetition
    local VehicleSeat = vehicle:FindFirstChildOfClass("VehicleSeat")

 -- Something that is `nil` means that it does NOT exist
   if VehicleSeat == nil then
       -- Use a different method
       VehicleSeat = vehicle:WaitForChild("DriveSeat",5) -- Assuming A-Chassis vehicle
       -- Wait for 5 seconds in case the seat may pop up
   else 
        -- Since a VehicleSeat exists, it is inferred that the model IS a vehicle!
        return true
   end

 -- Check if the VehicleSeat exists again from the second method
   if VehicleSeat then
       -- The VehicleSeat exists! It is a vehicle!
       return true
   end

   -- This model failed the checks and is NOT a vehicle
   return false
end

local vehicles: Folder = workspace.Vehicle

-- Find cars that are already existing
for index: number, vehicle: Instance in vehicles:GetChildren() do
    if isAVehicle(vehicle) then
        lightreflector.register.addVehicle(vehicle, CheckForRegLightValue(vehicle), determineIntensity, determineColor)
    end
end

-- Find cars that MAY spawn
vehicles.ChildAdded:Connect(function(vehicle)
    task.wait() -- a-chassis init reasons
    if isAVehicle(vehicle) then
        print("Indexed vehicle")
        lightreflector.register.addVehicle(vehicle, CheckForRegLightValue(vehicle), determineIntensity, determineColor)
    end
end)

-- Find cars that are removed
vehicles.ChildRemoved:Connect(function(vehicle)
    if isAVehicle(vehicle) then
        print("Removing car")
        lightreflector.register.removeVehicle(vehicle)
    end
end)