The Human Machine Interface

In the years after the Second World War, as cars required less human input to run, manufacturers needed to economise and cars became more a way of life for many rather than a lifestyle option, the HMI became drastically simplified. Drivers of the emerging budget car class, such as the Volkswagen Beetle or Fiat 500, had nothing but a speedometer and fuel gauge. Even in the 1950s, 2CV owners were still dipping their tanks to figure how much further they could go.

But such bare and functional HMIs were short-lived. Compare, for example, the dashboard of the last Ford Anglia to that of the first Ford Escort. The simple horizontal speedometer of the Anglia was replaced with two prominent circular gauges, displaying revs and speed adjacent to four smaller dials showing fuel level, oil pressure, water temperature and battery charge. From this point in the late 1960s, the HMI advanced rapidly, with every new model having more gadgets and displaying more information. Some instruments, like rev-counters, became genuine selling points.

It was at this time that the space between the transmission tunnel and the dashboard evolved into the centre console, as seen in the beautifully angular interior of the 1974 Aston Martin Lagonda. But not only was the driver sitting low in a cockpit and now with important buttons never far from the fingertips, but so too did they look through their single-spoke steering wheel to marvel at the world’s first digital dashboard. The fact the technology at this stage was little more than a novelty, providing no greater functionality than conventional analogue dials, seemed entirely beside the point…

This was also a charge levelled at the first head-up displays seen in 1988 on the Nissan Silvia S13 and Oldsmobile Cutlass Supreme. These early HUDs simply projected the vehicle’s current speed onto the windscreen. Yet while not adding much to the HMI experience in their infancy, the technology of the digital dashboard and HUD would go on to be major developments in car ergonomics.

These innovations led to a period of simplification and refinement of the HMI in the 1990s and 2000s, producing some of the most ergonomic interfaces. Compare the HMI of the W140 (’91-’98) and W220 (’98-’05) Mercedes S-Class and this refinement is apparent. The dashboard of the earlier car, while not necessarily ugly or difficult to read, was undoubtedly more complicated than the latter. Displays for fuel consumption, water temperature and oil pressure were all contained within a single dial, whereas the semi-digitised dash of the W220 displayed its important information with four backlit dials.

The MPG information was displayed digitally and the oil pressure gauge was done away with all together as Mercedes considered it superfluous in a car so sophisticated and reliable. This simplification extended to the centre console. The seemingly limitless sprawl of buttons in the W140 was replaced with a central screen, while the essential controls for HVAC or seat adjustment remained physical. Buttons also appeared on the steering wheel, allowing the driver to change radio stations or scroll through menus without taking their hands off the wheel.

While the physical HMI of the early 2000s was intuitive and reliable, the digital interfaces were often frustrating. But systems evolved, and BMW’s infuriating but game-changing iDrive showed a whole new direction, allowing drivers to navigate digital menus without taking their eyes off the road for an extended period of time. Once refined and simplified, what resulted was the Human Machine Interface at its most effective: you operated a single, physical control, but watched the results on a screen. When perfected by the likes of not only BMW but Audi and Mercedes-Benz, it seems things could not get any better. And for once, we were right, for they were about to get a whole lot worse.

This golden age was indeed short-lived. With the release of the first iPhone in 2007, and, pivotally, the release of Tesla’s 2012 Model S, the touchscreen became the HMI of the 2010s. The early Model S was equipped with a 12.3-inch digital dashboard and 17-inch central touchscreen. While navigating a map is certainly intuitive on a touchscreen, having to navigate a menu in order to prod HVAC controls is not.

It’s a familiar complaint Ti readers have read in countless articles and doubtless experienced for themselves in one form or another. But so too is it leading to another problem, as yet far less widely debated. With the near universal adoption of the touchscreen, proprietary infotainment systems such as Apple CarPlay and Android Auto are now available on everything from a Dacia to a Ferrari. Indeed these two manufacturers, so far apart in the automotive market, share a common need for systems such as CarPlay, because it’s now the only way their customers get to know where they’re going.

Because the development of your own HMI is expensive, difficult and time consuming (just ask McLaren and its miscreant IRIS system), it’s just easier in so many ways to fit CarPlay or Android Auto instead. Your car screen now looks like your smartphone screen, everything is where you expect it to be, and works how you want it to work. What could possibly be wrong with that?

Well, like those boring homogenous electric powertrains I mentioned at the start, so too should a car’s HMI be an exciting expression of personality. Should. Unfortunately, CarPlay strips a car of said personality, reducing the interface to that of every other car and, indeed, every other smartphone. The interesting analogue HMI, such as the dial bearing steering wheel of the TVR Cerbera, is dead.

Even digital dashboards can be interesting (remember the floating tachometer in Lexus’ LFA?) but when Ferrari no longer provides its own navigation in the Purosangue, forcing owners to use CarPlay or Android Auto, losing the rev-counter every time it’s activated, you have to ask whether a good idea has been taken too far. And, even whether the democratisation of the decent HMI is the straightforwardly good thing it at first appears to be.