From Practical Classics – October 2017
This is a Concorde moment. Once upon a time, we could sip champagne in comfort whilst travelling at 24 miles a minute. Years before that, mankind was dancing about on the moon and planning excursions to the outer reaches of the galaxy. And there was once a time when motorists could glide across the earth on a bed of nitrogen gas in a vehicle that could maintain a constant ride height irrespective of load, untroubled by undulations and broken tarmac. 
The hydropneumatic Citroën was an engineering masterpiece of comfort, safety and control efficiency, unveiled to a world enduring suspension made up of medieval leaf springs and 19th century coil spring technology. As Citroën drivers wafted about serenely, the rest of the world failed to appreciate the benefits.
And now, for successive years, we’ve been told we want sporty cars. That means even MPVs and SUVs have stiff suspension springs and low profile tyres, vulnerable to our appalling road surfaces. See how occupants of modern cars jiggle about in their sports seats on the way to work, enormous alloys thumping into potholes. And for what? To live out the fantasy that you might one day tackle the Nurburgring?  
In 2017, we took a great leap backwards. Yes, I know the manufacturing cost was as prohibitive as supersonic flight was to most of the airlines but it doesn’t mean Concorde wasn’t dynamically superior to a lumbering Jumbo. As a regular user of cars with both springs and hydropneumatics, I am convinced the latter should have been the future. It’s so typical of the human race. Mankind pulls a blinder and then throws it all away.

How it works
Following in the footsteps of André Citroën, visionary Citroën CEO Pierre Boulanger instigated the next chapter of Citroën’s long history of innovation with the line: ‘Study all possibilities. Even the impossible.’ He assigned designer Paul Magès to Citroën’s development department in 1942, who was introduced to aeronautical engineer André Lefebvre and sculptor Flaminio Bertoni (the uncompromising stylist responsible for the Traction Avant, 2CV, H Van, DS and Ami 6). Paul’s suspension design brief was to enable ‘fast travel on poor road surfaces.’
What he came up was a high pressure gas and oil system (or ‘Oléopneumatique’), designed to enable suspension, steering, brakes and gearshift to work in harmony with each other, with the entire system operating from an engine driven pump.