We're sat in the passenger side of a Lexus GS 450h driving along a highway. Which might not sound like all too unusual an experience. Only this Lexus is the Highway Teammate and it's driving itself; steering, changing lanes, accelerating, braking, monitoring surrounding traffic to ensure safe merging with traffic and, ultimately, blowing our minds.

This is not a drill. We're not in some pre-defined scenario with a load of "car extras" also speeding along the highway like some fictional movie. Nope, this is Toyota's autonomous technology in full swing on real roads in Tokyo. Make no mistake: driverless cars are coming, and coming faster than you might think.

Although the terminology is up in the air right now. Toyota, like Volvo, prefers to use the word autonomous. Audi calls it piloted driving. We prefer to call it driverless, because it cuts through the yawnsome legal terminologies and, well, makes everything sound a lot more fun, doesn't it?

But this Toyota real-world self-driving-car experience isn't technically driverless. There's a Toyota representative sat in the driver's seat, his hands and feet visibly strayed from steering wheel and pedals respectively. After all there are laws that prevent actual driverless cars from being on the road and the intention of the technology, at this stage, is to act as a safety assist - it's not so you can fall asleep at the wheel for a couple of hours' kip.

But how does Toyota's Highway Teammate and autonomous technology all work? In its current guise the technology utilises 11 sensors - six lasers (LIDAR) and five milliwave radar - along with one camera to read lane markings and determine surrounding vehicles' positions. For the purpose of commercialisation Toyota intends to reduce the number of required sensors and, therefore, the cost base.

Using these sensors Toyota is able to not only determine other vehicles on the road around the car, but identify what they are by their size - so whether it's a large truck, standard car, or smaller motorbike, everything is identified. Think of it like a bat using echolocation: receiving the relevant signals back lets the car's systems know what surrounds it (it can even measure oncoming speeds).

A central display in the Highway Teammate shows everything occurring in real-time in a virtual environment that mirrors reality. Not only is it mesmerising to watch, it's a useful visual aid to build the confidence and trust between driver and car - something that Danny Shapiro, Nvidia senior director of automotive, told us was an essential when we spoke to him back in June 2015.

READ: Driverless cars and the future of self-driving tech: Nvidia's Danny Shapiro explains what to expect and when

However, hearing about trust from someone's mouth (however senior they may be in their field) is quite different to sitting in an actual car cruising down the highway and merging lanes at 80kmph. But the Toyota technology handled a number of scenarios well: once, from our secondary point of view in a chase vehicle, we watched a truck speeding past the Highway Teammate, which although already indicating to merge lanes delayed its response; another time, when busy traffic filled a significant portion of the neighbouring lane, the car detected a spot ahead and accelerated to merge, leaving ample space. Toyota has designed the system to be always looking for the best-case scenario.

However, the system can only respond to what it knows. Here's where there whole autonomous vs driverless scenario comes into play: the system is able to hand back the controls should it need to - which it does by a visual and audible warning - to the driver.

In addition the reason Toyota is, for now, restricting the tech to the highways is for two main reasons: one, unknown variables, such as car doors flinging open, kids running out into the road, and so forth; two, that the company needs to pre-map roads to feed the system so it can calculate the best route without depending on unreliable out-of-date maps.

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Toyota has been mapping Japan's highways, because it's essential to know exactly what a given road system is like. How many times has a satnav tried to send you the wrong way down a one-way system, or has Google imagined a road that doesn't exist any more? By having the full and relevant navigational data, paired with dual GPS antennas (those round shapes to the top rear of the car) to correspond the data, Toyota can deliver a safe experience. Anything out of the ordinary and the car will hand-over controls again.

So what comes next? The company is talking about autonomous technology being an on-the-road reality by 2020. We suspect it will arrive like most current car tech does: as an optional extra. But in true on-the-marketing-speak format Toyota did tell us that its ultimate goal is "to provide the freedom of mobility and safety to all people".

From our point of view we think there's wider scope for standardisation. If all companies working on driverless/autonomous car technologies formed an alliance where the free flow of information and communications between vehicles on the road were to make for a safer experience, we'd have a wider and safer network. Big data from the cloud is the key, which isn't something that, for the time being, Toyota is integrating into its system.

But that's not to take away from the Highway Teammate: it's a huge achievement to have it out on the road, especially given how it's visually like almost any other car you're likely to see. It's exciting stuff to see the future, now.

We didn't take a car for a drive, a car took us for a drive. Now there's something we never thought we'd be saying, let alone in 2015.