The imagination is an amazing thing. In my mind I can fly if I so desire, my fist held out directly in front of my face, my other arm straight at my side. The wind as I hurtle through the skies tugs at my hair, grasping at skin and clothing. Through clouds and out the other side, the cities and villages and patchwork fields blur beneath as I roll and dive, just as I did decades ago in the local swimming pool, when I only dreamed of flying.

Heroic deeds are easily accomplished in the mind - wading through countless bad guys, each one felled with quick efficient strikes. Blink and I am careening through space, next in some manic action sequence with vehicles pin wheeling over my head from the force of some impact ...

In the last seven years I have driven a great many of England's roads, clocking up just under 200,000 miles along the way. Driving is not what I do for a living, just something that I do in getting to places I can earn a living, or to participate in life.

In this time I have never been involved in a road accident or seen one happen, but I have quite often driven past the consequences. Tonight is an example.

Heading east along the M4 – blue skies and the odd white cloud bidden by the first hints of autumn wind. Just after the last Swindon junction the vista suddenly becomes a sea of brake lights and flashing hazards. Everything on my passenger seat deposits itself into the foot well.

Over the next twenty minutes the traffic slowly concatenates towards what must be the scene of an accident, while police, fire and ambulance efficiently hurtle past on the hard shoulder.

Another twenty minutes and I am crawling through a scene of devastation, I have never seen anything quite like it.

In the central lane there is an upside down silver car, pointing to roughly four o'clock as I sit. It looks like a Ford Focus but I cannot be sure and for all intents and purposes seems to have been dropped from about twenty foot onto its roof, reducing the car to half its previous vertical height. A punctured air bag flaps free in the small gap that was a drivers window, now no more than an inch or two upside down high.

For seventy yards leading up to the felled vehicle the central reservation guardrail is bent over at an angle into the opposite side of the motorway. This is a strong metal fence over one meter high that has been designed to stop lorries and cars travelling at speed from crossing into incoming traffic.

It has not been bent over from horizontal impact but looks to have been forced over because something landed on it and skidded along its surface for a good fifty yards. Minds eye serves an image of a car doing the sort of trick you see kids doing with skateboards along the top of low steps and guardrails.

As unlikely as this seems, evidence would indicate this may have been the case - a number of cars travelling in the opposite direction around this point look to have veered off suddenly and are scattered at various positions along the motorway and hard shoulder, most with two or three punctured tires.

Stones are strewn across both sides of the motorway. We are not talking a few handfuls but what appears to be most of a pebble beach. There is no convenient shingle lorry pulled to a sudden stop with its tailgate hanging down as explanation, just wide deep tracts of churned mud from the central reservation. Several traffic officers have pulled brooms from the back of their cars and having climbed over the bent fence are stood in the middle of the westbound motorway, ushering these stones back towards the central reservation. Queued traffic looks on, awe has not yet given way to impatience or anger.

Back on the eastbound side of the accident, the hard shoulder is a collection of fire engines and police cars. Further on the hard shoulder and first lane of the motorway mirrors the westbound, with countless vehicles at odd angles seemingly having come to a sudden halt. The embankment is littered with dazed humans. Just a bag full of minutes ago they were hurtling oblivious to some destination – just another journey.

A paramedic attends to a blanketed but seated female. She is staring through all the pandemonium as if looking into another world. I cannot see any ambulance so assume the medic was left behind and the ambulance now screams towards the nearest accident and emergency.

A policeman once told me that speed is the multiplier that can be applied to assess the severity of any accident. But he saw very few accidents that could not have been avoided if one or all of the drivers had been actively thinking about driving.

As I look back at the vehicle, so flat and utterly defeated, with its pummelled bodywork and shredded air bag fluttering in the wind - nothing in this realm of my imagination now faced with a hard physical reality, can possibly conjure a force powerful enough to render this vehicle through this path of devastation to this end.