Aside from sounding like it received its moniker from BMW's product department, the S-Voice Drive driving mode is an extension of the's S-Voice voice-command app that adjusts the system in a few very important ways for drivers.
First, it allows the driver's interactions to be mostly hands-free. When in this mode, S-Voice Drive can be activated with a spoken command, rather than pushing a button. This allows drivers to keep both hands on the wheel. Simply say, "Hi, Galaxy" and the device springs to attention, ready to accept your voice commands.
Next, Drive mode simplifies the onscreen interface, presenting the driver with a mostly blank screen showing large text prompts instructing the driver that S-Voice Drive is ready to accept commands and displaying a few examples of what sort of commands can be accepted. No app icons are present, and there's nothing too distracting to the driver.
Driving mode also makes voice command a persistent part of the UI, even when you're doing something else. Start navigating and you'll see a black bar along the bottom edge of the screen with a microphone icon indicating that, even outside of the S-Voice interface, the phone is still listening for you to say, "Hi, Galaxy."
To access Drive mode, simply double-tap the Home button beneath the S4's screen to access S-Voice, then say "Driving mode on".
What commands can you input? What can't you do?
However, this persistent hands-free interface comes at a cost. Simplifying the interface and streamlining for driver friendliness means that when S-Voice is in its driving mode, the dozens of functions that it normally is able to perform are reduced to just a handful.
Call and Text commands allow the driver to initiate hands-free calling or dictate an SMS message with a few short commands. The calling bit is pretty self-explanatory; just say, "Call James Franco" and if he's in your address book, the phone should start ringing once S-Voice Drive confirms that it has heard you properly. SMS dictation is a bit more complex, but basically S-Voice Drive will ask to whom you want to send the message and then what you want the message to say. After S-Voice Drive reads back your message, you can either say "Send" or, if the message sounds incorrect, simply restate it.
Saying "Navigation" triggers S-Voice Drive to ask where you want to go, then initiates Google Maps turn-by-turn directions to an address or point of interest that you state. I found that this bit of the S-Voice interface sometimes required at least a single touch-screen tap to chose from the list of possible destinations that the Google Maps app would present once its search was complete. Address entry was more straightforward, dropping straight into navigation without a prompt for confirmation -- which was good when S-Voice Drive understood me perfectly, but not so great when it misheard "10th" instead of "Tehama" street.
Users can also tell S-Voice Drive to play music, specifying an artist's name or song title. Simply saying, "play music" picks up where Samsung's TouchWiz Music player left off the last time you listened to something. I'd prefer the option to specify Google Play Music or a streaming app like Pandora, but I can understand why Samsung chose its own app: for simplicity's sake.
Finally, I was able to check the current weather in the area by saying "weather." I could also get current conditions in other cities by saying, for example, "weather in San Diego" or get a forecast by saying, "weather tomorrow." S-Voice Drive could also read aloud news headlines, schedule calendar appointments, and store voice-dictated notes in the S Memo app.
What I liked best about S-Voice Drive is that its speech recognition is conversational and casual. Rather than issuing stiff commands like "weather," I could ask it "What's the forecast for San Diego tomorrow?" I also liked that the system would render conversational responses, such as, "It's going to be sunny and clear. Don't forget your sunglasses."
Likewise, I was able to string together complete commands, rather than waiting for prompts. Rather than saying "Text" and then waiting to be prompted for the recipient and message, I could just say "Text James Franco; Message I'm going to be a few minutes late." and, after S-Voice Drive read back the message, I could then just say "Send" and be done. Addresses can also be input in one fell swoop, a la "Navigate to 235 Second Street" or "Navigate to 5 Guys Burgers and Fries."
Multitasking with voice commands
S-Voice's driving mode is designed to be used without touching or watching the screen, but it does take advantage of the Galaxy S4's split-screen ability to give the driver persistent access to the "Hi Galaxy" spoken prompt and to display extra information when available.
For example, after asking S-Voice Drive to initiate navigation, I can ask it for the weather to have a five-day forecast momentarily appear on the bottom half of the screen. After a few seconds, the forecast disappears and the navigation expands back to full screen. If I then ask S-Voice Drive to send a text, the recipient and the message preview will again occupy the bottom half of the screen.
Rotate the phone into a landscape orientation and the split becomes a vertical one, with S-Voice Drive's information displaying on the right half of the screen.
The inevitable Siri comparison
S-Voice has been compared to Apple's Siri before -- a fight that for Samsung's voice-search application. However, much has changed since then, and both systems have evolved quite a bit. S-Voice Drive brings one very strong advantage to the table: it doesn't require any physical input from the driver, while Siri requires tapping or holding a button to activate.
By responding to a spoken prompt rather than a button press, the person behind the wheel is able to to keep their hands on that wheel, which is the safest way to drive. Siri may offer more functionality than S-Voice Drive (particularly when the Samsung app is in its driving mode), but S-Voice has all of the important functions for driving covered. Finding out how tall Abe Lincoln was can wait until after the trip.