This article was originally published on April 16, 2015. It was updated on Jan. 20, 2016.

How long will it take? It depends on whom you ask. Hopeful Silicon Valley engineers think we'll see them on the road within five years. More conservative auto industry executives peg their debut around 2030. Wall Street analysts are somewhere in the middle.

Still, there's one thing almost everyone agrees on: The era of the autonomous car is rapidly approaching. The benefits to society could be immense: fewer accidents and parking garages, more productive commutes and less traffic congestion.

For investors, the upside could be equally as impressive. Although the industry remains in its early days, several companies are poised to take advantage of the shift. Below are four stocks that offer exposure to the coming autonomous car revolution.

A moonshot

If you're not doing some things that are crazy, then you're doing the wrong things. -- Larry Page

Source: Google.

Alphabet (NASDAQ:GOOG) (NASDAQ:GOOGL) CEO Larry Page believes in taking what the company calls "moonshots": radical, high-tech bets with the potential to revolutionize an industry. X, the tech giant's research lab, has been working on an autonomous car since 2010. In 2014, the company unveiled its prototype -- a car without a steering wheel or pedals. 

The opportunity for Alphabet's technology is almost unknowable -- it hasn't even unveiled a concrete business model. It has ruled out manufacturing the vehicles itself, stating that it wants to seek partnerships with existing firms, but what form those partnerships will ultimately take remains up in the air. In December 2015, reports indicated that Alphabet planned to partner with auto giant Ford to bring its technology to market, but those rumors remain unconfirmed. For the time being, Alphabet is still very much dependent on its core search business, but the company could look quite different several years from now.

Forget tablets -- it's all about the automobile
Like Alphabet, chip maker NVIDIA (NASDAQ:NVDA) is currently wed to an entirely different business model and market. Its graphics processors are primarily sold to PC gamers and professionals, and they compose the overwhelming majority of its revenue.

But NVIDIA's system-on-a-chip platform, Tegra, might overshadow its graphics cards at some distant future date. NVIDIA hasn't had much success in getting smartphone or tablet manufacturers to use Tegra, but the processing power it offers has attracted the interest of automotive manufacturers pursuing autonomous vehicles. At the 2015 Consumer Electronics Show, NVIDIA announced Drive PX, an autonomous car platform powered by its Tegra X1 chips. German auto giant Audi announced that it would use NVIDIA's platform in the development of its future autonomous cars.

At CES 2016, NVIDIA doubled down, unveiling the second-generation Drive PX platform. With far more computational power, autonomous cars that utilize NVIDIA's Drive PX 2 can track many more objects.

Ultimately, as the demand for autonomous vehicles grows, NVIDIA could become a major supplier.

An after-market solution
Delphi (NYSE:DLPH) is one of the largest automotive suppliers in the world. Its business centers primarily on supplying electronics to automobile manufacturers, and in the future, that could include technology for autonomous vehicles.

Delphi has been retrofitting existing cars with a variety of electronics that allow for autonomous capabilities. Last year, it announced that one of its cars had completed a coast-to-coast drive (San Francisco to New York) almost entirely by itself. At CES 2016, Delphi announced a collection of new technologies, which it calls vehicle-to-everything (V2E). As its name implies, V2E allows connected vehicles to communicate with their surroundings, including streets, signs, and other cars. Delphi's V2E even includes people -- a special chip implanted in smartphones can alert an autonomous vehicle to crossing pedestrians.

Delphi's established supplier relationships could give it an advantage, allowing it to sell existing automakers the technology they need to make their vehicles capable of autonomous driving.

The eyes of the vehicle
In contrast to Delphi, Mobileye (NYSE:MBLY) is far less established. Its history as a publicly traded company is rather short, and it hasn't been consistently profitable, but it may offer more upside.

Mobileye's business centers on the creation of software for automotive monocular cameras -- cameras mounted on a vehicle that allow it to see its surroundings. Its technology allows for semi-autonomous functions, such as lane assist or automatic braking, and with future development, it could underpin more advanced aspects of a fully autonomous vehicle. Mobileye remains a small player in the market, but continues to innovate. At CES 2016, it unveiled a new system, Road Experience Management (REM). Using REM, connected cars send and receive bits of mapping data from the cloud, relying on each other to drive autonomously.

Mobileye is the most speculative stock on this list, and its technology could be disrupted (Alphabet and Delphi are banking on LiDAR laser remote sensing system, for example) but Mobileye gives investors the opportunity to purchase a piece of a company that is almost singularly focused on autonomous driving.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.