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British engineering firm JCB’s new Hydromax land speed record challenger has reached 208mph to exceed the current speed for the faster hydrogen-powered combustion car as its testing programme wraps up.

The firm is aiming to set a new hydrogen land speed record with the machine on the Bonneville Salt Flats in Utah in August, repeating its success in setting a diesel land speed record with its Dieselmax challenger in 2006.

The car has reached 208mph during its testing programme in the UK, which already eclipses the current mark for a hydrogen-combustion car – although the record is unofficial because it wasn’t during a sanctioned event. Regardless, the ultimate goal is to eclipse the current record for a hydrogen fuel cell car.

Steve Cropley visited the team during testing to find out how the project is developing.

Inside JCB’s UK test programme

For a week and a half the weather at RAF Wittering was hardly ever right, varying from driving rain to extremely gusty crosswinds; both entirely wrong for a long, narrow land speed record car urgently aiming to crack 200mph.

The JCB Hydromax team had set up a tent base for their all-British record breaker beside the pristine 1.7-mile main runway at Wittering, near Stamford, with the aim of getting as close to 200mph as possible before packing the car up and flying it to Wendover, Utah, nearest city to the Bonneville Salt Flats that are the home of world land speed record-breaking. 

In the early days of August, a couple of weeks from now, the car is scheduled first to take part in the Southern California Timing Association’s time-honoured Bonneville Speed Week, its two turbocharged hydrogen digger engines each producing 600bhp, 200 below maximum. 

Then in the second week, with the engines now making full power, Hydromax will tackle official FIA-sanctioned world records, on the way speeding past the 350mph mark set 20years ago by the slightly heavier, less sophisticated and 10% less aerodynamic JCB Dieselmax of 2006 which, while burning now-unfashionable diesel fuel, was similar in size and layout to Hydromax.

It’s of zero importance to history whether Hydromax beats Dieselmax; their different fuelling puts them in very distinct record categories. But there’s a big physical similarity between the pair — and JCB engineers make no secret that their Dieselmax experience was a major aid to the hydrogen project.  

The cars are both very long, needle-nosed single-seaters — and both are built to contain the powerful physique of the redoubtable Wing Commander Andy Green, go-to land speed record driver of the past three decades and the world’s only man to have beaten the sound barrier on land (which he did at 763mph in 1997). 

Apart from the tyre valves, Green wryly points out that he is the two cars’ only common component. His job is to beat the current record for hydrogen cars, set at 302.877mph in 2009 by a fuel cell streamliner, the Buckeye Bullet 2, designed by a team of Ohio University students and elevate it as far as possible. The current record for a hydrogen combustion car stands at an enticing 185.5mph, set by a BMW research prototype in 2004. With a bit of luck, they might have beaten this at Wittering.

JCB’s eye is particularly on pulverising this piston record; in fact they might have beaten it at Wittering. Fuel cells in vehicles are all very well, but after a five-year, £100million research programme that is about to bring hydrogen engines into diggers, its technical staff has reached the firm conclusion that hydrogen piston engines are by far the best option on compactness cost and durability grounds, among others. 

The hydrogen units can be surprisingly similar in construction, affordability, component supply, power output and operator procedure to the 185,000 engines the company already makes annually.    

Hydromax and Dieselmax share the same wheelbase and are both four-wheel drive designs with each wheel-pair driven by its own much-modified version of JCB’s 4.8-litre four-pot digger engine. The two engines “talk” to one another electronically to deliver matched revs and power, and each drives its wheel pair through an XTrac six-speed transaxle (modified from racing applications). The whole thing weighs around 2.8 tonnes, a few percent lighter than its predecessor.   

Aero requirements plus the need to accommodate the Hydromax’s bulky twin 700bar hydrogen tanks has required an increase in Hydromax’s 9.75-metre overall length by 560mm, while the cabin has been moved forward 450mm, also for packaging reasons. 

The massive tubular chassis and amazingly compact mult-link independent suspensions are the work of Prodrive, the Banbury race engineering group, who also designed and built Andy Green’s hugely strong carbon composite driver’s cell carried inside the chassis.

The tyres look similar to those from Dieselmax, but are new Goodyear units that as well as advancing the safe speed (JCB won’t say hope far) use more modern carcass construction and more sustainable materials, Engineers say that where Dieselmax was “limited on tyres”, Hydromax is not.  

Hydromax’s CdA is 10% lower than its predecessor mostly through the assistance of CFD (computational fluid dynamics), a science that shapes and predicts airflow over cars much better than it could 20 years ago. 

Among bigger tweaks, its results encouraged engineers to lengthen Hydromax’s tail for minimum departure turbulence, and to position its fin ideally for high speed stability. The rear extremity of the car is complex in design; it contains two parachutes (regular and reserve) for braking from high speed, and is reinforced sufficiently to allow it to be propelled to 40-50mph by a Defender Octa, after which it accelerated rapidly away in first gear. 

Despite having to obey aerodynamic rules, Hydromax’s looks considerably more modern and sophisticated than its predecessor, mainly through the influence of JCB’s design director, Ben Watson, whose daunting day job is to make diggers look desirable. He gave Hydromax its “jet fighter” cockpit, lowered the nose, raised the body on its tyres (because they “grow” in circumference at high speed), refined the surfacing and ditched Dieselmax’s ugly snorkel airscoop in favour of a subtly-placed, low-drag NACA duct.

Nobody at JCB or Prodrive wants to talk top speeds, but given that the new car is lighter, more slippery and more powerful in its ultimate form, there’s good potential for Andy Green to exceed Dieselmax’s 20-year old mark of 350mph in the new car.

But success, everyone points out, can be as much down to weather and surface, as man and machine. The track, usually about 11 miles long, has been as short as five miles. The surface itself can vary in consistency, too, and past Bonneville Speed Weeks have been cancelled due to flooding. Small wonder the crew at RAF Wittering were frustrated by difficult weather…

Experiencing the Dieselmax at speed

When we arrived, they’d already been on site for a week and a half, with a few days to go. We heard a lot about JCB’s rationale for preferring hydrogen piston engines to fuel cells (the central rationale for building the car) and had plenty of chances to study the car’s graceful shape, and to see its wonders under the skin Engineers were having trouble with two things: the fit of a new set of panels that carried a new livery to dramatise our photographs, and a problem with the bleeding of the all-important cooling system that depends on a replenished ice supply rather than airflow.

But finally, around 3pm, we spectators were invited into a pedestrian corral halfway down the big runway to see the car go. This was to be Run No14, we were told, but the earlier ones hadn’t been energetic like this. They were just to get the wheels turning.

The pushing Octa (the team name for it is evidently Octa-pushy) got the car fairly slowly up to speed, then the engine fired, a deep bass bellow — or farther, two of them — and the action began. The long Hydromax, tiny but highly visible because of its new livery, shot off the front of the Defender and began to bolt for the horizon.

Without ceremony, with barely any impression of the violence of performance, it rushed past and away towards the horizon. There was no need to batter walls of air aside; it just cleaved it like an arrow. We kept needing to refocus, because it kept going faster until out of sight. The crew, some apprehensive and some a bit morose, suddenly perked up. 

Then came news that Andy Green had managed to snap into third gear and accelerate, not possible before. As a result, he’d scored 177mph, not far short of the practical limit on this track, even with two parachutes and four large motorsport-spec discs to calm your forward motion. Two-point-eight tonnes creates plenty of inertia at 177mph.

Having proven it can beat the hydrogen piston mark the project now moves to Utah to do so at an officially sanctioned venue. Can this JCB-Prodrive alliance again prove the strength of British engineering? We’ll know soon.

Opel will give UK subsidiary Vauxhall more engineering freedom to adapt its cars for its home market, in line with an ongoing commitment to preserving the British marque's role in the Stellantis group.

Stellantis – parent company of Opel-Vauxhall, as well as other European marques Alfa Romeo, Citroën, DS, Fiat, Lancia and Peugeot – recently announced that it would channel the bulk of its future investments into its four best-performing global brands, raising questions about the viability of others.

It chose Peugeot, Ram, Jeep and Fiat on the basis that their "multi-regional presence" gave them "the greatest scale and the highest potential for profitability", while also announcing that DS and Lancia would be repositioned as "specialty brands" focused on their home markets of France and Italy.

The move would seem to represent a rationalisation of Stellantis's sprawling portfolio aimed at reducing complexity - but Opel boss Florian Huettl says the Bedfordshire-born Vauxhall marque will continue to play a "very clear" role in the company, and its cars in the UK could become more bespoke than they have been in more than four decades.

Vauxhall has not made its own cars since effectively merging with Germany's Opel in the early 1970s and has been a UK-only operation for almost as long, sparking questions over its continued viability as a marque in its own right.

But asked whether there remains a place for Vauxhall in the new Stellantis corporate structure, Huettl told Autocar: "Opel and Vauxhall have a very clear identity and a very clear role within the group," referencing Opel's performance in Germany – where it is Stellantis's best-selling brand – and in the UK, where the Corsa and Frontera both rank in the top 10 most popular cars.

He added that the brand will in fact take on an expanded engineering role as part of a move to boost its competitiveness in its historic UK homeland, where it is currently outsold by French sibling Peugeot.

"There's no doubt about the importance of Opel and Vauxhall," said Huettl, "and what we will again discuss with you in due time is that we intend to give more possibilities for more differentiation and more adaptation of Vauxhall to the UK market than what has probably been done in the past.

"We have a specific project together with our Vauxhall team [...] to make sure that the cars, when it comes to the execution especially of the chassis specificities, clearly respond to what we need," he added, in possible reference to the far worse state of UK roads compared with Germany's.

He did not give specifics about the extent of work that will be possible, and it remains to be seen which model will be the first beneficiary, but he emphasised that the company will work to meet "the specific needs of UK customers". 

Tunnels are used to carry traffic through some of the most extreme terrain on the planet and they help ease journeys with reduced travel time.

While most tunnels offer a short underground burst of driving, some are much longer. Here are the world’s 10 longest road tunnels that use cutting edge technology to make their construction possible and to keep drivers alert while passing through their extended subterranean length.

Ryfylke Tunnel, Norway – 8.98 miles (14.46km)

The Ryfylke Tunnel is the longest undersea road tunnel in the world at present and stretches some 8.98 miles between Stavanger and Ryfylke. Norway developed the Ryfylke Tunnel to reduce reliance on ferries. It is now part of its Rogfast project to connect several islands with undersea tunnels, and this means Ryfylke is likely to relinquish its title as this building work continues.

Opened in 2019, the Ryfylke Tunnel took seven years to build and a toll is charged to help recoup the cost of construction.

By the time the Ryfylke Tunnel started operating, it had cost 6.4 billion Norwegian Kroner (£460 million) to complete. Electric cars are subject to a 50% discounted toll charge.

Descending to 285-metres under the sea at its deepest, the Ryfylke Tunnel consists of two separate tubes to carry traffic in opposite directions. Each tube has two lanes and the tunnel is capable of carrying up 10,000 vehicles per day.

Zigana Tunnel, Turkiye – 8.99 miles (14.48km)

Close to the northern coast of Turkiye, the Zigana Tunnel runs through rugged mountain rock to bypass the Zigana Pass that becomes blocked by snow in the winter.

Work started on the Zigana Tunnel in 2016 and it was finished in 2023. It is Turkiye’s longest road tunnel at 8.99 miles long and it reduces the journey via the exposed Zigana Pass by five miles. It also cuts the journey time in summer months by around 20 minutes.

Consisting of two separate tunnels to keep traffic flows apart, the Zigana Tunnel was built using the New Austrian Tunnelling Method. This system adapts to the rock as excavation continues and uses a spray-on concrete to create the walls.

There are 16 laybys in each of the tunnel’s tubes, as well as six ventilation shafts. It was also built with 40 connecting tunnels between the pair of tubes, plus nine transformer rooms to house the Zigana Tunnel’s electric power.

Muzhailing Tunnel, China – 9.46 miles (15.22km)

A great many challenges faced the designers and builders of the Muzhailing Tunnel in China’s Gansu Province. For starters, it’s built at high altitude and also in an area of active seismic activity, which means it’s prone to earthquakes.

Although not ideal conditions for creating one of the world’s longest road tunnels, the build used a technology called NPR anchor cabling. This secures the structure into the surrounding rock and allows the tunnel to withstand deformation as the ground moves.

In common with most modern road tunnels, the Muzhailing Tunnel consists of two separate tubes, each carrying the stream of traffic in the opposite direction to the other.

Construction work on this tunnel started in 2016 and reached its finish in 2024, with further complications to the build caused by the thin air at its high altitude and its effect on the workers.

Now complete, the Muzhailing Tunnel is widely studied by tunnelling experts for the way it deals with such difficult terrain.

Tiantaishan Tunnel, China – 9.67 miles (15.56)

It cost 2.75 billion Chinese Yuan (£300 million) to complete the Tiantaishan Tunnel, which is something of a bargain in the world of road tunnels. Started in 2016, the Tiantaishan Tunnel was finished and working by 2021, which is again something of a record when it comes to build time.

All of this is even more impressive when you consider the high altitude of the tunnel and the bitterly cold weather in Shaanxi Province in northwest China.

Tiantaishan Tunnel, China – 9.67 miles (15.56)

When construction started in November 2016, there were 2000 workers spending their shifts underground in the Qinling Mountains. They also lived there for the duration of the build work.

As part of the construction of the Tiantaishan Tunnel, a new smart lighting system was developed that delivers a more natural light inside its depths. This set-up also provides different light patterns and designs on the tunnel’s walls to ward off boredom as drivers traverse its 9.67-mile length in either of the three-lane tunnel tubes.

Gotthard Road Tunnel, Switzerland – 10.46 miles (16.84km)

Previously the longest road tunnel in the world, the Gotthard Base Tunnel in Switzerland has slipped down the ranking as new projects have overtaken for length. However, the Gotthard has been in operation for much longer than any other in the top 10 as it opened in 1980.

Work started on the Gotthard Road Tunnel in 1970 and it carries traffic to a maximum height if 1175-metres (3855-feet), which is higher than Yr Wyddfa (Mount Snowdon) in Wales.

Gotthard Road Tunnel, Switzerland – 10.46 miles (16.84km)

It takes around 13 minutes to drive through the Gotthard Road Tunnel as the 80kmh speed limit is strictly enforced. There is also a toll charge to pay for using the tunnel and it’s capable of carrying up to 24,000 vehicles per day.

The Gotthard Base Tunnel is unusual in modern road tunnelling for using a single tube to carry both directions of traffic. In 2016, 57% of the Swiss population voted in favour of building a second Gotthard road tunnel in a referendum.

Jinpingshan Tunnel, China – 10.90 miles (17.54km)

While all of the other road tunnels in the top 10 are open to the public, the Jinpingshan Tunnel restricts what traffic can use it. This is because the tunnel was built to provide access to the Jinping Dam, which is the world’s highest dam, and access between this and another hydropower dam.

The Jinpingshan Tunnel runs through an area noted for its geological activity in south-west China. This is partly why access to the tunnel is limited, and also because of security surrounding the hydroelectric complex at the dam.

Jinpingshan Tunnel, China – 10.90 miles (17.54km)

At its deepest point, the Jinpingshan Tunnel runs 2375-metres beneath the earth’s surface, and more than half of the tunnel’s entire length sits at more than 1500-metres deep.

It took five years to build the Jinpingshan Tunnel and, at the time, was the longest tunnel made with a blind heading. This is where each end of the tunnel is started simultaneously and meet in the middle. Total cost of Jinpingshan Tunnel came to 1.3 billion Chinese Yuan (£146 million).

Zhongnanshan Tunnel, China – 11.21 miles (18.04km)

The Zhongnanshan Tunnel is not far from the Tiantaishan Tunnel but outdoes its near neighbour in overall length and how deep it travels under the Earth’s surface. With a maximum depth of 1640-metres, the Zhongnanshan Tunnel is among the deepest in the world.

Despite this, it still took only five years to complete the tunnel. Work started in 2002 on the Zhongnanshan Tunnel, and it was the longest tunnel in Asia when it opened to traffic in 2007.

Zhongnanshan Tunnel, China – 11.21 miles (18.04km)

It cost around 3.2 billion Chinese Yuan (£350 million) to complete the Zhongnanshan Tunnel. This makes it one of the most expensive road tunnels to date in China. Three ventilation shafts provide fresh air to each of the two tunnels, and each tube carries traffic in the opposite direction to the other, so the streams are never together.

Along its 11.21-mile length, there are different coloured lights and patterns projected onto the tunnel’s roof, and artificial plants to provide stimulation for drivers and prevent fatigue.

Yamate Tunnel, Japan – 11.3 miles (18.20km)

The Yamate Tunnel in Tokyo, Japan is like London’s Blackwall Tunnel but on a grand scale. Where the Blackwall Tunnel is a mere three quarters of a mile long and is as close as 1.7-metres from the riverbed, the Yamate Tunnel runs to 11.3 miles and passes as much as 30-metres beneath the Japanese capital city’s population.

The Yamate Tunnel still holds the honour of being the longest urban tunnel in the world.

Yamate Tunnel, Japan – 11.3 miles (18.20km)

It took 15 years for the Yamate Tunnel to be completed, with delays due to objections from residents and environmental concerns. However, the tunnel was given the go-ahead as it would ease traffic on Yamate Street that runs above the tunnel.

Both of the 11-metre diameter tubes that form the Yamate Tunnel have emergency telephones positioned every 100-metres along their length. There is also a sophisticated filtration system to remove particulate emissions from the air extracted from the tunnels.

WestConnex, Australia – 13.67 miles (22.0km)

The WestConnex Tunnel was finished in November 2023 and is part of a plan to ease congestion in the city of Sydney. To date, the tunnel is the largest road infrastructure project ever undertaken in Australia and the 13.67-mile tunnel is part of a longer overall 20.5-mile stretch of traffic-reducing motorway.

This will eventually link Sydney’s suburbs, airport, north shore, and city centre. The land above the WestConnex Tunnel has mostly been given over to parks, playgrounds, and open space for the city’s inhabitants to relax.

WestConnex, Australia – 13.67 miles (22.0km)

The WestConnex Tunnel is the longest underground stretch of public road in Australia, and it’s thought to have cost A$10 billion (£5.1 billion).

This figure set a new record for transport spending by the New South Wales Government, and it’s estimated the fully completed project will come in at A$45 billion (£23.1 billion). However, the government also states the tunnel contributes to A$22 billion (£11.3 billion) in savings due to reduced travel time and journey reliability.

Lærdal Tunnel, Norway – 15.23 miles (24.51km)

Topping the longest road tunnels in the world is the Lærdal Tunnel in Norway. This 15.23-mile underground construction was started in 1995 and opened to the public in 2000. It took some 20 years to agree to the construction of the tunnel, which cost 1.1 billion Norwegian Kroner (£85 million) to complete, which represents great value in the world of roads tunnelling.

It was so much cheaper to build than most tunnels as the nature of the rock means the tunnel doesn’t need to be lined – and nor does it have to be made earthquake proof as they no not occur with any severity in Norway. The tunnel connects Lærdal and Aurland and consists of two tubes, each carrying traffic in a single direction for safety.

Lærdal Tunnel, Norway – 15.23 miles (24.51km)

While it’s the longest road tunnel in the world, the Lærdal Tunnel is also one of the most lightly used. On a typical day, it carries around 2050 vehicles, which is largely due to its remote location 180 miles to the northwest of Oslo.

To alleviate the monotony of driving through the world’s longest road tunnel – which is also straight throughout - this Norwegian project is divided into four sections, each separated by a large cave with parking areas. The caves have blue and yellow lighting to give the feel of a Norwegian sunrise, which is thought to give drivers’ brains a boost when they are tired. Police cameras have also been installed to combat speeding.

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