On May 27, the public got a chance to see and try out the prototype. What was it like, riding in the Google self-driving car?

Two people got in the prototype, buckled up, and used a smartphone app (or pretended to) to tell the car where they wanted to go.

The Google car has no steering wheel, no brake pedal, no accelerator, no park-forward-reverse — so the two passengers knew immediately they would ride in the car, not drive it.

One of them pushed the “start” button, and the car took them to the street address they gave it. When they arrived at their destination, the car turned itself off — or the passengers pressed the “stop” button — and the trip was over.

The takeaway? Here’s one: The Google self-driving car will take you to work — but if you want to stop for donuts on the way, you’ll have to instruct the car through your smartphone to pause on its trip to your office — then begin a new trip into the donut shop parking lot and park — then leave the parking lot, and resume the trip to your office.

The Google prototype
is the first 100 percent “self-driving,” or “autonomous” car.

What is different about the Google car is that it is 100 percent self-driving. There is no steering wheel, no brake pedal, no accelerator. If you were riding in the car, you couldn’t drive it if you wanted to.

Google, in statements released May 27 when it showed its prototype to the public, said it decided allowing a rider in the car to “seize control” of the car in an apparent emergency would merely increase the danger to the car and its riders. So it removed the steering wheel, and other controls, so the passengers could play no role in driving the car.

How does the Google car know what road to take, where to turn, and how to get to the destination the rider gives it? It follows Google’s highly detailed maps, loaded into its software. During the trip, it uses a global positioning satellite feed and its radar, sensors and lasers to confirm its exact position on the map.

Every stop sign, traffic light, one-way sign is on the map, and the car’s sensors monitor everything that moves or is on the roads nearby for 600 feet or so in every direction, so the car will always avoid hitting another vehicle, a bicycle, or a pedestrian.

For the time being, the car will go no faster than 25 miles per hour. Google does not contemplate the car being used on the highways to drive from one city to another.

And Google’s progress so far? It says it will build 100 prototypes and test them on public roads starting in late summer, 2014. At some point in 2015 or beyond, Google will begin to sell the cars for use where the law permits. To date, four U.S. states allow the testing of self-driving cars on public roads: California, Nevada, Florida, and Michigan.

The auto makers — in contrast to Google, a computer company — are adding “self-driving” features to regular production cars.

Where the Google car will have no steering wheel or other controls for a driver to use, the auto makers will keep the driver in charge of their self-driving cars.

And that is the greatest difference between the Google car, and all the other self-driving cars under development. The auto makers will retain the steering wheel and other driving controls, and add “self-driving” features to their standard production cars.

What are some examples of “self-driving features?” Volvo says its prototypes so far can “safely follow a car down the street, adjust the car’s speed, and merge, all without the driver’s assistance.”

Volvo says it hopes to have some ordinary drivers as well as experts working with its first “autonomous car” in Gothenburg, Sweden, where Volvo is located, in 2017.

At Mercedes, the company says the autonomous sedan, like the Google car, will be “completely” autonomous, although it will keep the steering wheel, brake pedal, accelerator, and other driver controls, and the driver will remain the driver — and remain in command of the car.

Like the Google car, the Mercedes car will follow detailed maps of the roads and highways the car will be traveling — and Daimler touts its progress so far, boasting that already its autonomous sedan has been able to follow, without the driver’s help, the same sixty-mile route between Mannheim and Pforzheim that Bertha Benz drove “more than 125 years ago when she set off on the world’s first long-distance drive.”

Mercedes says it would like to see its self-driving cars in production by 2020. It adds that an essential part of any completely self-driving car will be accurate and detailed maps. Google, of course, already has the maps that Mercedes needs.

Dieter Zetsche puts the question: Do you want to ride in a car that will haul you somewhere — or do you want a car you can drive?

Daimler Benz CEO Dieter Zetsche — known to Americans from the years he spent turning Chrysler around — was, at the 2014 Detroit Auto Show in January, the strongest voice defending the traditional automobile against the concept of the “driverless” Google car.

The world’s automakers are preparing self-driving cars, he said, and these are “real” cars: Cars with steering wheels, brake pedals, and accelerators. Cars that drivers can take over when conditions warrant, or when the driver simply wants the pleasure of driving. You can’t have that, he stressed, with a car (like the Google self-drive) that has no steering wheel, brake pedal, or accelerator.

“What Google is building,” the Mercedes CEO said, “may have its place as the car that will take you home after you have had too much to drink — but is that what we really want [in a car? — a car that can ‘take’ someone incapable of driving somewhere — and ‘take someone’ is all it can do?]”

“At Mercedes,” Herr Zetsche said, “we are pursuing the goal of accident-free driving. Our vision is that the driver remains in control, but if he does something that puts the car or the passengers at risk then the car will step in. That is our vision of the autonomous car.”

And for the next few years, this may be the competitive difference: If Google — the “computer” company — stays in the car business, it may have the first self-drive on the market, and its self-drives may make good “specialty” cars: taxis, for instance. Or delivery vehicles, going to programmed destinations.

The auto industry, in contrast, “sells the adventure of the open road,” an “anti-Google” sentiment expressed time and again at the Detroit Auto Show. Consumers who buy cars — the industry says — will prefer cars they can drive.