Painting trains: Full steam ahead

The motorcar had little impact on 20th-century art. There are a handful of good car-paintings, and they're all oddities. Somehow, painters couldn't make the automobile work for them. The aeroplane didn't fare much better. (Yet think how cinema has adored both cars and planes.) But the train – surely that's another story? Paintings have loved trains. Was it simply all that steam?

Art in the Age of Steam, at the Walker Art Gallery in Liverpool, is a marvellous exhibition. It's full of masterpieces and surprises. Painting takes the train, and the journey is spectacular, with works by Manet, Monet, Daumier, Pissarro, de Chirico and Hopper. There are photos, posters, prints and some film clips, too. And for a surprise, would you expect to find the name of Vincent Van Gogh on the roster of railway artists? His ink drawing of La Crau from Montmajour, with a country train crawling through a patchwork landscape, is one of the exhibition's glories.

As a rule, I'm against anthologising art by subject matter. The theme tends to dominate the art and the art tends to be of variable quality (bad work as well as good will fit the bill). So it's lucky that there are so many superb train-pictures. It's lucky that the gallery could get hold of most of them.

The show starts with a significant cancellation. Turner's Rain, Steam and Speed – The Great Western Railway of 1844 is the first great train-painting and still the most famous. But it's now too fragile to travel and is represented here by a film of it hanging in the National Gallery, with visitors occasionally stopping and blocking our view, which is nice (though it would be nicer still if it were a live broadcast). Turner's landscape is sublime, apocalyptic. The Home Counties go into meltdown, as this new miracle-cum-monster, its infernal fires burning, hurtles towards us down a diagonal of soot-blackened track. But even Turner can't disguise what an unspectacular contraption this primitive train is – a big tin can with a spout on wheels.

Adolph Menzel's view of The Berlin-Potsdam Railway, painted a few years later, sees this even more clearly. It looks down, unsublimely, on a stretch of scrubby edge-of-town countryside, with a squat little train trundling energetically through it. The steam train here isn't remotely diabolical. It has already become what it is in so much children's fiction – something rather sweet.

Both these pictures take a distant view. That's characteristic. Artists in the early decades of railway locomotion might be excited by the train and its powers. They didn't take a close-up interest in its machinery. Stubbs's paintings of horse-drawn carriages are fascinated by their axles and suspension. No painter shows a similar practical curiosity in the wheels and pistons of a steam engine – nor, for that matter, in the epic construction schemes the railway brought with it, all the tunnelling, cutting, levelling and bridge-building.

It was the jobbing printmakers and photographers who paid attention to these things, and they're well represented here. Even before Turner, an illustrator like John Cooke Bourne was depicting, with sensitivity and wonder, the cavernous, shadowy architecture of the Great Ventilating Shaft, Kilsby Tunnel – the kind of amazing sight that the painters wouldn't look at.

Their aversion may seem strange. Surely the railway had artistic potential: massive hollows and arches, wrought-iron cathedrals, mighty earthworks and viaducts, sheer walls of cut rock. But artists, who'd lately been so enthused by Gothic architecture, classical ruins, Alps and ravines, couldn't delight in their modern, industrial equivalents. They didn't even take to rail-tracks, those new Roman roads running straight for miles, a textbook exercise in perspective, though they appear in contemporary engravings and photos.

But then, as the non-history of the car in art suggests, we shouldn't expect painting to be a comprehensive document of its age. Oil painting is not a medium of record. However visible the railways were, there was no necessity for painting to notice them at all. It took precious little interest in factories, and factory chimneys, and their spectacular gaseous emissions.

So Art in the Age of Steam is not exactly the story of a love affair. Nineteenth-century painters didn't fully embrace the railway. They took the train very much on their own terms. For example, they looked for the human story.

In the train compartment they found an interesting kind of theatre, cramped, class-segregated. See Augustus Egg's The Travelling Companions, with its two young ladies, seated symmetrically in their identical, enormously voluminous travelling costumes. Or see Daumier's The Third Class Carriage, a dark container full of heavy bodies pressed together.

And in the big railway stations, they found a panoramic stage, on which the classes mingled and a hundred things happened at once. William Powell Frith's huge The Railway Station – it is St Pancras – is a frieze of humanity, dense with social detail and passionate incidents.

And then there's the steam. In Impressionism it takes on a life of its own. It's like a flag, a flare, a great white billowing sign, which stands for a train, even when the train itself is hardly visible or has left the scene. It is a totally manipulable element. Painters can put it where they like, shape it how they like. Look at the works of three lesser-known Parisian artists, Paul Helleu, Norbert Goeneutte and Giuseppe de Nittis: they revel in steam's freedom, scattering it across a townscape or landscape in random fusillades. The train is only a pretext.

This is the most intense part in the show. In Paris, in the 1870s, painting finally registers the shock of the railway, the way it had become a weird fixture of modern life. In Monet's Gare St Lazare, soft bright vapour comes up against hard black ironwork, in a strange symphony of sharp silhouettes and thick blurs. Manet's enigmatic The Railway, set outside the same station, places a smart young woman and a girl abruptly against a rigid grid of iron railings. Gustave Caillebotte's Le Pont de l'Europe, also adjacent, stands top-hatted gents against a criss-cross of massive girders. In both, a cloud of steam from an unseen train appears in the background.

And the most imaginative section is the sequence – mostly 20th century – devoted to the poetry of the railway. It brings together realists, Surrealists and semi-abstracters, to show how the train got into the mind. The Italian Futurist Gino Severini does the train as pure brain-shattering energy. In de Chirico's The Anxious Journey it is a sudden, remote vision, appearing through a gap in a colonnade. Edward Hopper's Railroad Sunset evokes the loneliness of an empty track in the middle of nowhere.

There are dreams of leaving and dreams of waiting. The Lineman, by the Dane Laurits Andersen Ring, stands with his back to us, motionless, as he gazes down the line, looking for the train to come round the bend. And there's that beautiful watercolour by Eric Ravilious of an empty compartment. Through its window you glimpse a white chalk horse on a passing hill.

Art in the Age of Steam: the art is often extraordinary, and there's much more than I've mentioned. But all through there are also conspicuous and revealing absences. You notice how no fine artist can just sit down and paint a train, as Stubbs could paint a carriage (that's left to the populist train-painter, Terence Cuneo). You notice how the passenger's experience is never properly represented.

In 1833, one of the earliest witnesses to rail travel recorded that "the most remarkable movements of the journey are those when trains pass one another. The rapidity is such, that there is no recognising the features of a traveller." (And he was only going at 20mph.) Everyone has observed this thrilling phenomenon. No fine artist has painted it. Art and the train: the encounter is always partial and always slightly odd. The railway never settles down into being a normal subject.

And that's not surprising. What this show tells is a tale of two technologies, and the obvious fact is, they were not made for each other. One was a revolutionary form of transport technology, which created some breathtaking new sights. But the other, oil painting, was a very old visual technology, with its established traditions and trajectories. Occasionally, startlingly, their tracks crossed. Most of the time they occupied parallel universes.

Art in the Age of Steam, Walker Art Gallery, Liverpool (0151-478 4199), to 10 August