An autonomous car built by Google. Google The driverless car race is heating up.

There are now 30 companies involved in the development of autonomous vehicles, according to research from analyst firm CB Insights.

The companies were identified using CB Insights' investment, acquisition, and partnership data.

Apple, Google, and Uber are among the tech heavyweights looking to cash in on autonomous cars, while traditional automotive firms like Audi, BMW, and Daimler are also investing in research.

Not everyone is sharing their progress, though. While Google is being relatively open about its developments in the driverless car space, Apple is more tight-lipped.

However, a clue dropped this week on where Apple could be developing its first car, which is highly likely to be an electric, autonomous vehicle.

German publication Frankfurter Allgemeine reported that Apple's first car is being developed in a lab in Berlin, Germany. The report also stated that Apple is considering manufacturing the Apple Car in Vienna, Austria, possibly teaming up with vehicle engineering and contract manufacturing firm Magna.

Here's the full list of companies working on self-driving cars:

Apple

Audi

Baidu

BMW

Bosch

DAF

Daimler

Scania

Volvo

Delphi

Ford

GM

Google

Honda

Hyundai

Jaguar Land Rover

Mercedes-Benz

Microsoft

Mobileye

Nissan

Renault

Nvidia

PSA Groupe (includes Citroën and Peugout)

Tata Elixsi

Tesla

Toyota

Uber

Volkswagen

Volvo

Yutong

Companies leading the charge on the driverless car race say they will be safer and more efficient than cars driven by humans.

One automotive firm, Volvo, has pledged to make all of its new cars "deathproof" by 2020, according to CNN.

"With the development of full autonomy we are going to push the limits of automotive safety," said Volvo safety engineer Erik Coelingh. "If you make a fully autonomous vehicle you have to think through everything that potentially can happen with a car."