"That green button under your foot is the kill switch," we're told as we strap into the five-point racing harness. "Lift your foot off it and the engine will stop." 

The engine in question reverberates through the carbon fibre cabin of Shell's UrbanConcept vehicle, a super-efficient car that we're now driving slowly round a closed track in London's Olympic Park. The looming shell of the Velo Park dominates the horizon, its celebration of speed a stark juxtaposition to today's challenge.

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"The course is not about speed, it's about efficiency." Those words circulate as the concept car rolls smoothly across the Tarmac and the first corner looms. Lose too much momentum and you'll waste fuel picking up speed again; accelerate too hard and the single-rear wheel drive will twist the vehicle needing a costly correction. 

The engine is from a scooter and the cabin is sparse. It's an empty shell designed to be as light as possible. It's not lost on us that the weakest link in this chain is the weight of the driver, and the relative lack of skill.

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That's a challenge that's faced by Eco-marathon participants, who build cars of this type in the UrbanConcept or Prototype classes for Shell's competition. The UrbanConcept is a more practical design, something you might actually be driving in the future, with a seat, doors, there's even a sliding window you're unlikely to use. Shell even has a road legal version, adding luxuries like mirrors and indicators.

The Prototype by contrast is about pure efficiency, like piloting a sarcophagus, with the driver lying prone inside, with a small window to view the road ahead.

While most of the talk about Shell Eco-marathon is about engineering - its participants are engineering students from around the world - once behind the wheel, it's about the skill of the driver. Just like Formula 1 at the other end of the spectrum, all the research and engineering is just to put that driver on the course and let them perform.

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As we pull to a halt, the team is already opening up the engine bay and examining the fuel level. A serious shake of the head confirms what we already know: "not so good." We blame the weight of the driver, and seek consolation in a post-race doughnut. 

The UrbanConcept vehicle is easy to relate to and Shell is also going to be opening this up to autonomous vehicles in the near future. Sure, autonomous vehicles aren't that rare these days. Everyone seems to have one in development, with autonomous of self-driving features now available on a wide range of production cars.

Oxford Robotic's approach is different, because it doesn't reply on GPS. It uses a laser system for location identification, scanning and recognising the world around it so it can take control of the vehicle and drive it for you. The idea is to create a system that isn't dependent on other technologies like GPS, letting you put vehicles into locations that can't use satellite systems.

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This could be underground, warehouses, urban environments or in parts of the world that aren't covered by GPS, and give you a vehicle that can still perform autonomously. In the case of the Oxford Robotics concept, it knows the route it has to drive by recognising where it is, and drives us smoothly with no problems.

That's really what Eco-marathon is about. It's about approaching the problem in different ways and seeking answers by doing things differently. The focus of the student's course has an impact. Some may be working on ultra-low friction bearings, some might be looking at lightweight materials, some might be looking telematics, figuring out how to gather data in real time and pass that back to the driver.

As long as you stick to Shell's rules, then creativity flows and the variety of designs and solutions you'll see taking part is striking.

For the last 30 years or so, Shell has been running the Eco-marathon. It's a challenge to develop the most efficient vehicle possible, looking to push boundaries, but also the minds and skills of those who participate.

The concept for the Eco-marathon dates back a lot further - to the 1930s - when a challenge between staff at Shell in the US lead to a competition to see who could get the furthest distance on a set amount of fuel.

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The participants present a wide range of variety in design, budget, focus and even fuels. You'll find electric, hydrogen, bio-diesel and petrol. We stop by to see the contrast between Colchester Institute's Prototype design - including pieces salvaged from a washing machine, and handstitched plastic panels - and that of University College London, with a full carbon monocoque. 

While the designs are radically different that aims are the same: to seek out efficiencies, to improve the performance and take bold steps into how we engineer the future and how we think about our vehicles in the future. That and have a lot of fun, of course. 

The competition returns to London for the second year in a row in 2017, being held at the Queen Elizabeth Olympic Park in east London. Between 25-28 May, Shell will throw open the doors on the Make the Future Live festival, with free tickets for those interested in attending and taking in some of the marvels on show. You can find more information on the Make the Future website.