Despite the negative press Tesla's (TSLA -12.34%) driver-assist Autopilot system has attracted over the years, the technology has been a key selling point for its vehicles. Autopilot gives Tesla a way to show off how it can continually improve its vehicles through over-the-air updates, making them safer and bringing them closer to the electric-car company's goal to eventually make its cars fully autonomous.

Tesla customers are clearly putting the technology to use -- the company said on Twitter Wednesday that its customers have now driven over a billion miles with Autopilot engaged. This is an important milestone as Tesla ramps up vehicle production and deliveries, shipping more Autopilot-capable vehicles than ever before.

Tesla Model X interior with Autopilot activated.

Tesla's Model X. Image source: Tesla.

Getting to 1 billion miles

Tesla managed to rack up these 1 billion Autopilot miles in just over three years.

The electric-car company started building vehicles with sensors for Autopilot in late 2014. But full Autopilot features like lane keeping weren't released until late 2015. In late 2016, Tesla upgraded the sensors in its vehicles to ones that the automaker says will eventually enable fully autonomous driving.

Of course, not all customers use Autopilot. Though active safety features like emergency braking and collision avoidance are enabled by default, customers have to pay to get access to Autopilot's more advanced features. In addition, even when a customer has paid for Autopilot, the technology is not always activated; currently, the technology is designed primarily for use on highways.

Impressively, Tesla said earlier this month that its total fleet -- including all the vehicles it has sold before it started shipping Autopilot-capable vehicles -- had just crossed 10 billion miles. This means approximately 1 in 10 of these miles was driven on Autopilot. Presumably, if you excluded non-Autopilot vehicles from this math, the ratio would be even higher.

Suffice to say, as Tesla continues to ship more Autopilot-capable cars and keeps improving the technology through over-the-air updates, the automaker looks poised to rack up the next billion Autopilot miles much quicker.

Building a track record

The automaker boasts that this technology is improving driver safety. In the company's first-ever quarterly vehicle safety report in October, Tesla said in Q3 it registered "one accident or crash-like event [near misses as recorded by Tesla's Autopilot software] for every 3.34 million miles driven in which drivers had Autopilot engaged." This figure was 1 in every 1.92 million miles for those driven without Autopilot activated. 

The data Tesla gathers from vehicles on the road from Autopilot-capable vehicles ultimately helps the company improve the technology further by using fleet learning and by informing future over-the-air updates. The company expects that, over time, Autopilot will become increasingly safer.

The achievement of 1 billion Autopilot miles comes as Tesla is shipping vehicles in higher volumes than ever before. Deliveries of the company's newest vehicle, Model 3, surged in Q3. Model 3 deliveries during the period were up more than 200% sequentially. More vehicles on the road with Autopilot will help Tesla improve the technology even more.