As the saying goes, true creativity means having the freedom to fail. The automotive industry is known for its groundbreaking ideas, but they can't all be winners. Here are five innovations - some big, some oh-so-small - that just never caught on.
Volvo is a clever car company. Usually. But in 2007 it launched the Personal Car Communicator (PCC), a high-tech multifunction key fob that could (among other things) tell you if somebody was hiding in your car by detecting their heartbeat.
The system was first available on the S80 luxury sedan and was aimed primarily at female customers, especially in America, where, according to the television programmes obviously being watched by automotive engineers in Sweden, ordinary citizens were continually accosted by bad guys hiding in the back seats of their vehicles.
Cue image of shadowy figure in rear-vision mirror.
The feature was quietly dropped in 2011: Volvo North America spokesman Dan Johnston admitted to USA Today that "almost no one" was using it.
Joystick steering wheel
If it's good enough for Knight Rider ... for some reason, carmakers can't shake the notion that a steering wheel can be replaced by a joystick. Crash safety is often the stated reason, but consider this: the industry started getting serious about this concept at the same time as home gaming consoles started to make a big impact.
Saab was completely serious about a drive-by-wire joystick car back in 1992. It created prototypes using the technology and even let motoring journalists drive them. Badly.
At the time, the Swedish company predicted production cars with joystick controllers within 20 years. And look at what happened to them.
Still, the idea keeps popping up in concept cars. Mercedes-Benz put a joystick in its 1996 F200 Imagination, while Toyota did the same in its 2009 FT-EV city car. Good luck with those.
Liquid tyre chain
The 1969 Chevrolet Caprice Coupe came with an option called the liquid tyre chain. When it snowed, the driver pressed a button and pressurised containers sprayed a blended resin directly on to the tyres to improve traction.
The 60s were wild. By the time the 70s rolled around, Chevrolet had put the liquid tyre chain back in the boot and never mentioned it again.
A similar product is still available off the shelf in a can, but no carmaker since has been brave enough to embrace it as original equipment.
The history of aviation is littered with attempts at crossbreeding planes with road vehicles. Most are oddities, but two stand out as being recognisably cars. Neither caught on ... but you already knew that.
The ConvAirCar of 1946 was a purpose-built plastic-bodied car with wings and propellers on top. Only two were made: the first crashed after the test pilot mistook the car's fuel gauge (full) for the aircraft engines' fuel gauge (empty).
The Advanced Vehicle Engineers (AVE) Mizar of 1971 was similar in concept to the ConvAirCar: it was essentially a Ford Pinto with Cessna Skymaster wings and propeller on top. Both the car and aircraft engines were used for take-off, to shorten the distance required.
One of the Mizar prototypes crashed in 1973 after a wing failed, killing company founder Henry Smolinski. Lesson learned.
Or not. American company Terrafugia is now working on its own flying cars. One, the Transition, exists as a working prototype and is earmarked for production. It does 110km/h on the road and 185km/h in the air. Another is a hybrid for vertical take-off and landing.
The first completely electric turn signals were fitted to a Buick in 1938. Often known as "indicators", these comprise a system of four lights at each corner of the vehicle that can be operated by the driver to let other motorists know his or her intentions at intersections or when changing lanes.
The automotive industry and legislators have persisted with this concept, but indicators are still misunderstood and little used by drivers. They've just never caught on.