Tesla electric cars are empirically safe, but now company founder and CEO Elon Musk hopes a new Titanium under-body shield and deflector plates will offer Tesla owners "complete peace of mind."

When a handful of Tesla Model S electric automobiles went up in flames late last year, the company faced — and invited — some intense scrutiny. The stock price took a dip before fully recovering this year, and Musk repeatedly defended the car and company against what he called "an onslaught of popular and financial media seeking to make a sensation out of something that a simple Google search would reveal to be false."

Yet even as Musk sought to defend the car and remind people of its near-historic safety rating, he outlined a three-point plan for addressing concerns: Tesla invited the National Highway Safety Administration (NHTSA) to investigate the fires and quickly rolled out an over-the-air software update to existing customers that actually increased ground clearance at highway speeds. The company also amended its warranty to cover all cover fires, with the exception of those intentionally started by the car owners.

Now, however, Tesla has taken a step further. In a blog post on Friday, Musk announced that as of March 6, all Model S electric vehicles have been manufactured with three new under-body shields (one is titanium, the other two are aluminum). Each is designed to absorb, deflect or crush debris that may get caught underneath the car and keep them from damaging or puncturing the car's lithium ion battery pack which sits in the base of the car. The roughly 25,000 current Tesla owners can bring their electric cars into a Tesla service for a free retrofit.

Upon hearing the news, the NHTSA closed its investigation of Tesla's Model S and issued this statement:

Safety is our top priority. The National Highway Traffic Safety Administration has decided to close our investigation of the Model S Vehicle. NHTSA believes the company’s revision to the vehicle’s ride height and increased underbody protection should reduce both the frequency of underbody strikes and the risk of resulting fires. Consumers should have their vehicles serviced promptly once they receive notification from Tesla Motors.

The company also conducted more than 150 tests with the new undercarriage construction, including at least one in which a roughly $110,000 Tesla Model S drove over a largemetal car hitch (similar to what reportedly happened in one of the Tesla car fires). Musk provided a series of GIFs that show what happens when debris hits the new undercarriage construction.

"We have tried every worst case debris impact we can think of, including hardened steel structures set in the ideal position for a piking event, essentially equivalent to driving a car at highway speed into a steel spear braced on the tarmac," Musk wrote. He added that the changes should bring the risk of fire "down to virtually zero."

Still, Musk's frustration at making this most recent change is palpable; he essentially insists that they're not really necessary.

"The underbody shields are not needed for a high level of safety," he wrote. "However, there is significant value to minimizing owner inconvenience in the event of an impact and addressing any lingering public misperception about electric vehicle safety."