How do I make a player that sits in my vehicle turn invisible?

Place this in the seat or change the self variable to the path of the seat:

--[[ Unlimitus ]]--
-- Vehicle Seat Transparency Script --

local character = nil
local self = script.Parent

local debounce = false
function Touched (hit)
	if debounce == false then
		if character == nil then -- Prevents more than one player being affected by this function
			if hit.Parent:findFirstChild("Humanoid") then
				character  = hit.Parent
				wait(0.1) -- Wait for the character to sit
				if character ~= nil then
					if character.Humanoid:GetState() == Enum.HumanoidStateType.Seated then
						for _, child in pairs(character:GetChildren()) do
							if child:IsA("Accoutrement") then
								child = child.Handle
							end
							if child:IsA("BasePart") then -- BasePart is a class that all "Parts" fall under
								if child.Name ~= "HumanoidRootPart" then -- This is a brick not meant for view
									child.Transparency = 1
								end
							end
						end
						
						local function HumanoidJumped()
							if character ~= nil then
								if character.Humanoid.Jump == true then
									for _, child in pairs(character:GetChildren()) do
										if child:IsA("Accoutrement") then
											child = child.Handle
										end
										if child:IsA("BasePart") then
											if child.Name ~= "HumanoidRootPart" then
												child.Transparency = 0
											end
										end
									end
									if debounce == false then
										debounce = true
										character.Torso.CFrame = self.CFrame * CFrame.new(0, 1 + self.Size.Y / 2, -3)
										character = nil
										wait(1)
										debounce = false
									end
								end
							end
						end
						
						character.Humanoid.Changed:connect(HumanoidJumped)
					end
				end
			end
		end
	end
end

self.Touched:connect(Touched)