The once-futuristic concept of robotaxis (self-driving taxis) is rapidly becoming a reality. Already, these vehicles are on the roads in several US cities. Looking to invest in this exciting area of technology? Here are three S&P 500 stocks to consider buying.

Tesla

When it comes to self-driving technology, Tesla‘s (NASDAQ:TSLA) a leader. So naturally, it’s aiming to become a major player in the robotaxi space.

Now at present, we don’t know much about Tesla’s plans here. But that’s likely to change next month when the company holds its robotaxi event on 10 October.

CEO Elon Musk’s said this day will be the most “significant moment for Tesla” since the Model 3 was unveiled years ago. So investors are pretty excited.

The thing is though, Tesla robotaxis could still be years away. That’s because, in the US, Tesla doesn’t currently possess a permit for autonomous vehicle testing or deployment without a driver.

An additional issue to consider with this stock is the valuation. Currently, the P/E ratio is about 105. That’s lofty. Given the high valuation, this isn’t my preferred robotaxi play right now.

Alphabet

Another company that’s a leader in self-driving technology is Waymo, which is owned by Google’s parent company Alphabet (NASDAQ: GOOG). The key difference between Waymo and Tesla however, is that the former already has robotaxis on the road.

Indeed, it’s been trialling the technology for years now in cities such as Phoenix, San Francisco, and Los Angeles (I’m keen to try one out next time I’m in California). And earlier this month, it announced it’s expanding its services to Austin and Atlanta. So it has a clear first-mover advantage.

Yet that’s not the only reason to be bullish here. Another is the stock’s valuation. Currently, Alphabet’s a P/E ratio of around 21.5, which is low for a tech company.

On the downside, self-driving vehicle technology’s only a tiny proportion of Alphabet’s business. Most of its revenues come from digital advertising (which can be a cyclical business). So even if the company was to have success in the robotaxi space, there’s no guarantee that the stock will do well.

Uber Technologies

And this brings me to my last stock, Uber (NYSE: UBER). I believe this is the best way to play the robotaxi theme.

You see, Uber operates the largest rideshare platform in the world. Today, it has over 150m users globally. Given its size and reach, it literally has the perfect platform for any automotive company that’s looking to enter the robotaxi space.

Already, Uber has a major partnership with Waymo. I reckon that in the future, it could have partnerships with many other companies (maybe even Tesla).

Uber is uniquely positioned to offer tremendous value for autonomous vehicle players looking to deploy their technology at scale.

Uber CEO Dara Khosrowshahi

Of course, human drivers are likely to play a role at Uber for years to come. And this means there could be further issues with regulation, pay, strikes, and so on.

I’m excited about the potential here however. As a result, I’ve made the stock – which currently has a P/E ratio of around 30 – a large position in my portfolio.