The Autonomous Evolution

Humans and chimpanzees share 99 percent of their DNA. One percent is the difference between swinging through trees and building a civilization. The equivalent differentiator for the automobile may be the humble wheel-speed sensor, which first appeared in vehicles in the 1970s as part of early traction control and antilock braking systems. The ability to track precisely what speed each wheel is traveling has enabled or aided development of a raft of functions that make our cars safer, faster, and, above all, less reliant on drivers. How long until we're not needed at all?

The first four-wheel, computerized antilock braking system debuted on the 1971 Chrysler Imperial and still works the same way, rapidly pulsing the brakes when the wheel-speed sensors detect lockup.

Traction Control
Applies brakes to a slipping wheel and/or cuts the throttle. First appeared on the 1971 Buick Riviera.

Electronic Limited-Slip Differential
Brakes one wheel to send more torque to the opposite wheel.

Tire-Pressure Monitoring
Looks for speed differentials among the wheels to save the effort of using a $2 tire gauge.

Brake Assistant
Most drivers don't brake hard enough to benefit fully from ABS. With this function, computers amplify the input from the brake pedal.

Automated Brake-Force Distribution
Braking force at each wheel is adjusted to account for load transfer.

Electronic Stability Control
If ABS was the start of active safety, stability control was the first masterstroke. It's now mandated on all new vehicles, providing a vast platform for future autonomous technologies.

Trailer Sway Control

Rollover Mitigation

Lane-Departure Prevention
Working with a camera, stability control applies individual brakes to guide drivers who've drifted from their lane. (Some systems do this via electric power steering instead.)

Cruise Control
Early systems tracked driveshaft rotations, but the wheel-speed sensor provides a more accurate reading.

Auto Brake Prefill
When a driver abruptly lifts off the gas pedal, a throttle sensor tells the ABS to prepare for emergency braking.

Brake-Drying Function
Sensors used for the windshield wipers communicate with ABS to lightly brake during heavy rain to keep discs dry.

Hill-Start Assistant

Electronic Parking Brake

Hill Descent Control
Off-roading the easy way.

Adaptive Cruise Control
Combines cruise control with a forward camera or radar sensors.

Super Cruise Control
Cadillac is working on a feature that combines lane-departure prevention with adaptive cruise control.

Your new eyes and ears
In addition to the wheel-speed sensor, these are the technologies on the market today that will drive the car of tomorrow.

Radar sensors Envisioned as far back as Harley Earl's 1959 Cadillac Cyclone XP-74 concept, radar sensors are part of most active- cruise-control systems.

Ultrasonic sensors Used to detect close-up objects common in parking lots. Newer systems can work together to automatically bring the car to a stop if you fail to heed the beeps.

Camera sensors
Lane-departure warning systems typically rely on a camera mounted behind the windshield.

The University of Michigan, among others, is currently testing vehicle-to-vehicle (V2V) technology that will allow cars to inform each other of changing road conditions.

A car that knows how to get you somewhere should be able to get to that same place by itself.

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