MOUNTAIN VIEW, Calif — Three SUVs — looking like they just pulled out of a carwash — sit waiting in front of the Google X headquarters. The Lexus logo has been stripped from the front grill to make room for a sensor. One especially bulky sensor — maybe destined to be the Michael Douglas phone of the self-driving car era — twirls on the roof.

Myself and a herd of other journalists gather around and snap photos. A Google employee jokes that our hands will be cut off if we take photos inside the SUVs.

I’m assigned to car no. 2 and hop in the back. The first thing I do is buckle my seat belt. Two Google safety drivers get in the front seats to guide me through the experience. The one in the passenger seat balances a laptop that shows a real-time look at what the car’s sensors see around it.

A dumbed-down feed of the same data plays on a horizontal screen centered on the dashboard. Aside from that screen — and a gray box the size of a suitcase in the trunk — the interior looks like a typical SUV.

We start to pull away in manual mode. The driver demonstrates how easy it is to switch in and out of autonomous mode with a button on the steering wheel.

“You’re free to call for a disengage if you ever feel uncomfortable,” I’m told.

Our driver makes the first turn out of the parking lot on his own. Then the adventure begins.

A chime sounds. “Autodriving,” says a female voice over the car’s speakers.

The guy in the driver seat calmly rests his hands on his knees. I can’t see his feet, but he says they typically hover over the pedals in case he needs to brake to turn off autopilot. It hits home that the car is really driving itself when I hear the click of a turn signal and his hands haven’t moved.

We’re gently cruising down neighborhood streets behind Google X’s building. The roads are quiet and we don’t encounter any pedestrians. A bicycle looms ahead and we’re gaining on it. But the man turns left and we carry on, unaffected.

Things remain uneventful. I feel free of stress, like I might be riding with any trusted driver behind the wheel — until a curvy stretch of road. A car coming the opposite direction — at speeds that feel a bit fast for a side street — whips around the bend. The Google SUV brakes sharply and we come to a complete stop.

Did we need to brake? Putting myself in the car’s shoes (or should I say tires?), I probably would have slowed. But the complete stop seems like overkill given the open path on our side of the road. Our driver agrees and said it was the type of situation that would be logged and studied.

Google’s cars have been trained to be extremely conservative in unusual situations.

“They understand their own limitations,” said Dmitri Dolgov, principle engineer on Google’s self-driving car project, at a briefing later. “They understand that there’s something really crazy going on and they might not be able to make really good, confident predictions about the future. So they take a very conservative approach.”

Once the car passed us, we were quickly back on our way. Most of the side streets we traveled at about 15 mph.

Soon we would get a chance at faster roads.

We smoothly turn onto a main road and the SUV steadily accelerates to about 35 mph.

“Left lane change ahead,” calls out the computerized voice.

As an intersection nears, the turn signal clicks again, and soon we’re in the left-turn lane. The traffic light turns yellow, but the car doesn’t slam on the brakes. It feels like what any driver would do, given how close we are to making our turn.

During our turn — as we’re in the middle of the intersection — the Google SUV brakes for a momentary beat. After about half a second we’re quickly back on the gas and complete our turn.

So why the braking? As we made our turn, a car coming the opposite direction made a left from the middle lane, not the far left lane. I ask if that was what concerned the car. One of the Google test drivers pointed to a different car — one that had just turned right from the opposite direction — as the trigger.

Ultimately it was a minor hiccup and we still had time to complete the turn safely before our signal turned red. After a few more uneventful minutes on suburban roads, we looped back toward Google’s headquarters.

A few blocks away from Google I got another glimpse of the SUV’s cautious nature. A car, also with a stop sign, arrived at the intersection just after us. The Google car inched forward in two spurts. After a pause we drove through the intersection. We got through it fine, but slower than I expect most drivers would have. Soon we pull back in front of GoogleX’s building, a 14-minute ride in the books.

“Manual,” calls out the female voice as our driver took control again, and turned the car off.

If I was grading the SUV on our brief trek I would give it a B+. It wasn’t perfect driving, but safe and effective. Of course, our route wasn’t especially difficult. The real challenges come when pedestrians, inclement weather, construction sites and cyclists arrive.

Afterward I also had a chance to ride in Google’s prototype of a self-driving car. Because Google has two test drivers in vehicles at all times — and the prototype only seats two — I couldn’t ride it on public roads. So we had to settle for the experience of cruising around Google X’s rooftop.

The electric vehicle makes a distinct humming sound (notice it in the background here). I hopped in the passenger seat alongside another journalist. The interior — without a steering wheel or pedals — looks a lot like these photos I shared earlier in the year. The windshield isn’t glass, so some things look slightly distorted, as if looking through Plexiglas.

(On my way out I walked by another prototype — not part of Google’s demo day — that had a distinctly different interior, including a steering device that was mounted between the passengers and resembled a large metal ring.)

After we hit a “Go” button on the main console, and sat through a brief countdown, we were off on an automated course.

We looped around the roof at low speeds for 2 1/2 minutes, avoiding a pedestrian, a cyclist and a vehicle that Google positioned to showcase the car’s abilities. It handled each situation cautiously and effectively.

Google’s fleet of self-driving vehicles are covering between 10,000 and 15,000 miles a week. At the briefing, leaders of the project — including Google co-founder Sergey Brin — all raved about the improvements they’ve made of late.

A deadline of sorts continues to approach — the eldest son of Chris Urmson, director of the self-driving car project, turned 12 a couple weeks ago.

“In the U.S., you need a driver’s license in four years,” Urmson said. “And so our team is working really hard so he doesn’t have to.”