Car safety is big business, but some ideas don’t always catch on, writes Damien O’Carroll.

Heartbeat sensor

Back in 2006, Volvo came over all paranoid and unveiled a feature that would send you an alert on the keyfob if sensors detected a heartbeat inside your car as you approached it. Yes, really.

Volvo even pushed it in America as something for people so paranoid they thought that hordes of murderers were roaming the streets and somehow getting in and hiding in the back seat to get them, forgetting that Americans all have guns for that same reason.

This hasn’t stopped Hyundai reviving the idea in the latest Santa Fe SUV though, this time using motion sensors and positioning it for people so forgetful or distracted that they might leave a pet or sleeping child in the back.

Rocket brakes

Elon Musk may have revived this (possibly mad, possibly genuis) idea in one of his wild Twitter promises about the Tesla Roadster featuring small rocket thrusters to help it corner and stop, but it has been tried before.

In 1946 the Allegany Ballistics Laboratory in Maryland, United States, tested a Jeep with rocket thrusters attached to its front end at an upward-facing, 45-degree angle and found that they could halve the braking distance.

Of course, this did involve an amount of highly combustible rocket fuel to be stored in the car and the stop was reported to be brutal, however development of the idea did progress, although it never made it to a production car.

Water-filled bumpers

Seemingly ridiculously chunky and ungainly things when you first look at them, water-filled bumpers probably should have caught on (with a bit more refinement in the design department), largely because of their incredible effectiveness at mitigating damage in low-speed parking impacts.

A man named John Rich came up with the idea in the 1960s and produced and sold simple bolt-on water-filled bumpers.

His grandson tells the story of demonstrations that included a volunteer sitting in the boot of a car with his legs dangling down over the bumper and being hit at 15mph (24kmh) by another car with the bumpers and ‘‘hardly suffering any bruising’’.

Seat belt interlock

In 1973, the US Government passed a law that required all new cars to be fitted with an interlock that would not allow a car to start if the driver and front seat passenger weren’t buckled in.

While it proved to be wildly successful in improving seatbelt use, the law was eliminated the following year.

Why? Consumers hated it with a passion.

It seemed that American drivers would literally rather die than have their car tell them what to do and, after a huge wave of complaints to Congress, the law was scrapped and all we have had since was an annoying chime that nags us to belt up instead.

Safety turret

The one-off Sir Vival (see what they did there?) safety car designed and built by Walter Jerome packed some advanced safety ideas into a horrifyingly ugly package, but the one that arguably stood out the most was the driving position that saw the driver in the centre of the car (just like the McLaren F1), raised around 400mm above the passengers in a ‘‘turret’’ that provided almost 360-degree visibility.

It didn’t catch on because the car was also horrifyingly expensive and the safety turret was insanely complex – it couldn’t have conventional windscreen wipers, so the entire glass section rotated so that it could be cleaned by felt wipers mounted to the body.