Creating an iPad experience — on four wheels

June 13, 2013, 11:06 AM UTC

The largest, most expensive mobile device in most people’s lives is not a smartphone or a tablet. It’s their car. As microprocessors, GPS, and wireless have invaded the automobile, carmakers have begun to obsess about apps and interfaces that make such gadgetry work. Trouble is, old-line manufacturers tend to think in decades — car platforms cost billions to develop and take years to roll out — not trendy weekly or even daily iterations common in Bay Area software shops. To help create its new flagship computer system, General Motors turned to Boston-based consultancy InContext Design. Introduced in 2012 as the Cadillac User Experience, the system will eventually serve as the basis for so-called infotainment centers in new Cadillac, Chevrolet, Buick, and GMC vehicles, controlling everything from navigation and Internet radio to heated seats. Here’s a closer look at the design process.

1. User profiles

InContext began with some 140 field interviews in cities ranging from Boston to Beijing to assess what drivers really need. This led developers to create personalization options — so users can, for instance, configure their car displays to show the features they use most often — as well as an interactive iPad manual.

2. Cabin diagram

Research also revealed the amount of clutter in most cabins, the chaos of charger cables, plastic cups, purses, and wallets. GM designers used the information to create cabins with more convenient nooks and crannies to stow and plug in electronics, reconfiguring storage for media like compact discs and cassettes.

3. Whiteboard ideas

Together, GM and InContext designers crunched the data from the field to come up with new feature ideas, which included shortening the time it takes to enter an address into the navigation system, for example. Another improvement: aping the touch gestures popular on Apple and Google devices.

4. Paper prototypes

Before writing a line of code, designers created paper prototypes: hand-drawn interfaces on Post-its. Researchers sat with drivers, swapping different pieces of paper on the dashboard to gauge which sets of features and interactions worked best. That led to initial wire frames, which eventually yielded the final design.

This story is from the July 1, 2013 issue of Fortune.