RTI stands for Return to Invoice insurance. RTI GAP does exactly that, it pays the policy holder the difference between the insurers payout should you have be involved in an accident or be the victim of automotive crime and the actual amount you paid for the car in the first place. There for a total loss need not be a total catastrophe for you. If your car is stolen or declared an insurance write-off "Return to Invoice Gap Insurance" will refund to you the difference between what you paid for the car and your insurers depreciated valuation.
What would your position be if your car were stolen or written-off?
Insurance Companies depreciate cars by up to 60% over a three year period, therefore if you have a loan have you considered how you will settle it?
Even if your insurance payout covers your loan settlement, where does the deposit come from for your next car? - you don't have a part exchange!
If you are a cash car buyer, have you considered how you will fund the difference between the amount you paid for your car and your insurance payout? Will it be possible for you to replace like for like without adding more of your savings?