User Interface for A Car

Yesterday marked an important milestone for me as a driver. I finally replaced my trusted Honda Accord. I bought it in a hurry 3-days before I was to travel for business in 2004, and over the last 11 years it was reliable and easy to drive, required only the regular oil change and maintenance. Solid engineering.

Later on we bought another Honda, the Odyssey minivan to accommodate our kids. The sliding door is amazing convenient and it even comes with built-in vacuum cleaner. When we took a long drive to Disneyland and Legoland, the DVD-player helped to keep the kids entertained. It has navigation, rips CDs faster-than-real-time into MP3s and store the music files for playback later. So much technology, but it was also quite complex to operate.

The placement for my Honda Accord is a Mazda 3, and it has one of the best user interfaces in a car.

Physical Buttons

On-off functions are mapped to physical buttons. Press a button to turn off AC. If a function has various modes, there are two buttons to, one to go to previous/next mode, and another to return to the last mode.

Properties that can be adjusted are mapped to dials with no limits. Turn in one direction to increase value, opposite direction to decrease. This applies to audio volume, AC temperature adjustments or scrolling through menu items, which are always arranged horizontally or vertically in alternating order.

For the navigation/application screen, there is an over-sized controller knob, with buttons to allow quick access to music, navigation, and main menus. The return button is placed right where your thumb rests.

Heads-up Display

There is a translucent visor piece right between windshield and top of steering wheel, where navigation direction and current speed is projected. It overlays information in field of vision so it is not necessary to look down or at the screen.

Placement of the information depends on the eye-level of the driver and height of seat. Once I settled on a seat setting I liked, I had to adjust the projection settings so that the information is centered in the visor.


There is no needle, just a number for current speed. While it conveys the same information of how fast you are going, the secondary information of how fast you are accelerating is lost. Certainly the number is increasing or decreasing accordingly, but I find it much easier to see the needle move.

Manual Shifting

It is possible to drop a gear with the paddle-shift. The car knows if it is a bad idea to do so (for example, it'll avoid redlining) and will delay the downshift.

There is also a sport mode, where shift happens more immediately at the expense of fuel efficiency.

Shifting is one of the easiest ways to involve the driver and make the car more fun to drive. Not having to deal with a clutch does take away some confidence for me. But automatic transmission makes getting stuck in traffic that much easier to deal with.

Fuel Economy Tracking

There is an application that displays current fuel economy. It has a rolling chart of average miles per gallon and another mode where animation tells you that the regenerative brake system is charging a capacitor to save energy for use later.

The car does produce a range value, how far you can drive before having to refuel, so these extra data being displayed serve no particular useful purpose in my opinion. Perhaps to gamify fuel-conservation.

Automatic Adaption

The zoom level of the navigation map changes depending how fast I drive. Similarly, audio volume go up when speed increases to compensate for road noise. Headlights turn in direction of where car is going.


You never know when somebody is going to play MP3 streams with UTF-8 characters in ID3 tag. It works, even with Asian languages such as Traditional Chinese and Japanese.

Update Via SD Card

Download a utility from Mazda and install to desktop, and the utility will check automatically for updates. Downloaded navigation data is updated via SD Card. No need to visit dealer or pay hundreds of dollars for latest maps, at least for the first 3 years.

Why Not...

  • Remember seat and mirror settings for different drivers? There are two key fobs.
  • Allow auto-hiding some navigation items as a option?
  • One-press roll-down passenger-side window completely?
  • Allow access to the forward-facing camera? Use it to record?
  • One button to turn off the screen?
  • Search by business phone number?
  • Use a light to indicate that touch screen is responsive?