What a big month it’s been for driverless cars.

Ford announced that it would put fully driverless vehicles, without steering wheels or pedals, on the road by 2021. Uber said it would start offering autonomous rides in Pittsburgh — with an Uber employee at the wheel, just in case — by the end of summer. A new revolution in personal transportation is at hand.

“The world is changing,” said Hans-Werner Kaas, senior partner at McKinsey & Co.’s global automotive practice. “In the next few years, there will be a significant injection of technology” in new cars. Newcomers like Google, Apple and Uber want into the game, and “the incumbents of the past are trying to change as much as they can,” Kaas said.

To compete, automakers are entering into partnerships with ride-hailing services and buying technology companies. All the major car companies have set up research labs in Silicon Valley, where they’re trying to lure talent and expand their operations.

The revolution is being driven by technology, economics and social requirements. Sensors have gotten small enough and cheap enough to be mounted without adding so much cost that people won’t buy them. Artificial intelligence has advanced to make the sensors’ data intelligible. Crowded highways have made driving miserable in urban areas.

The companies pushing driverless cars insist they will be safer, and federal transportation officials agree. New regulations are expected soon from the National Highway Traffic Safety Administration, and the agency’s administrator has said that the rules are being written so as not to hinder innovation. Here’s what some of the companies are doing:

GOOGLE/FIAT CHRYSLER

Google’s autonomous vehicle program has 21 modified Lexus SUVs and 33 pod-like small cars that can drive themselves. In May, Google announced a deal with Fiat Chrysler Automobiles to more than double the size of its fleet by adding 100 Chrysler Pacifica minivans. For now, Google’s cars operate only under the oversight of company experts. Google is unlikely to manufacture its own cars for the mass market.

FORD

Ford announced plans earlier this month to make fully autonomous cars available for sale by 2021. The cars would have no steering wheels or pedals. At first they’ll be used for ride hailing and ride sharing, with sales to individual drivers an indeterminate number of years after that. Ford has made a $75 million investment in Velodyne LiDar, a northern California company that specializes in lidar, a technology that uses light to detect objects.

BMW

In July, BMW announced plans to release a fleet of fully autonomous vehicles by 2021 in a partnership with Intel and Israeli tech firm Mobileye. BMW has signaled ambitions to develop a range of autonomous vehicles with different levels of human and machine control.

GENERAL MOTORS/LYFT

This year, GM bought an autonomous car startup, Cruise Automation, and announced it would work with Lyft to develop driverless taxis. GM announced a $500 million investment in Lyft in January. The two companies announced plans to build an Autonomous On-Demand Network that will leverage GM’s autonomous vehicle development and Lyft’s ride-matching, routing and payment software.

TESLA

Tesla has been rolling out self-driving technology more aggressively than anyone. In 2015, the electric car company activated its Autopilot mode, which automates steering, braking and lane switching but requires the driver to remain attentive and keep his or her hands on the wheel.