I'm sitting behind the wheel of an idling car, waiting at a lonely red traffic light on an isolated strip of the Estonian coastline.
To my left is a small hut in which a gruff-looking road controller sits, peering out of a frosty window to check on the conduct of the passing vehicles. To the right is a sign that sets out the road rules for the journey ahead.
THE ICE-ROAD CODE
No driving after sunset
No vehicles heavier than 2.5t
No driving between 25km/h and 40km/h
They're not your normal kind of traffic rules. On this particular road, it is forbidden to wear a seatbelt: you might have to make an unexpected and speedy exit from your car.
You can't drive here after sunset, or with a vehicle over 2.5 tonnes. And it is strictly illegal to travel at between 25 and 40km/h (16-25mph). At those speeds, your car tyres will create dangerous vibrations that could crack the surface of the road, sending you and your vehicle to a watery grave.
The road ahead of me is made of ice. It stretches across the frozen surface of the Baltic Sea, connecting the Estonian coastline to the island of Hiiumaa. At 25km (16 miles), it is the longest ice road in Europe.
There are six official ice roads around Estonia. This past winter has been particularly harsh, allowing them to stay open for longer than usual.
Even in mid-March, with the warm spring sun beginning to melt the snow in the fields, the ice roads were still half a metre thick, enough to carry a steady stream of several hundred vehicles each day.
Perhaps the vibration warning is a myth, but I'm not willing to challenge it
Travelling on the ice is part of the history and culture of the Estonian islands.
Teutonic knights thundered across the ice on horseback to conquer the isles in the 13th Century. Villages here have been constructed by pulling supplies across from the mainland. Bears, wolves and moose venture to and from the islands in search of food.
These days locals look forward to the ice-driving season as it provides a cheaper and more convenient method of travel, compared to paying for passage on a vehicle ferry.
The traffic light turns green, and timidly I drive out onto the surface of the sea.
It's bumpy and slippery at the same time. A speed sign instructs me to drive at 70km/h (43mph), and as I accelerate the speedometer needle passes through the danger zone of 25-40km/h.
The ice surface stays firm. Perhaps the vibration warning is a myth, but I'm not willing to challenge it.
Once I'm speeding along the ice road, I understand why locals have no compunction about using it.
It feels incredibly safe. It's rough in some stretches, and slushy and slidy in others, but never do you have the sensation that the surface could give way.
A ship appears to be driving across a white field
At some points the track has deteriorated and large potholes have formed. Hitting these sends a jolt through the car and a huge spray of water and ice across the windscreen.
The road is marked out by juniper bushes about a metre high, which have been staked at wide intervals. In poor visibility, these shrubs are only means of finding the safe route across.
Huge cracks occasionally appear - not enough to break up the ice, but wide enough to create impassable gaps. At these points, the road controllers fix wooden planks as bridges.
On a sunny day like this one, the view is stunning. A desert of brilliant white stretches out in all directions. Small islands dotted about the bay appear as oases on the horizon.
Out of the right-hand window I spy a surreal sight. Several hundred meters away, a large ferry is keeping pace with the car.
It appears as if the ship is driving across a white field, but of course it is cutting through an ice-broken channel which runs almost parallel to the road. Locals tell me that jealous ferries sometimes "accidentally" veer off course and ram the ice road.
The coastline of Hiiumaa island looms ahead, and soon I'm pulling off the ice and on to solid land.
I get out and talk to the road controller, who tells me there hasn't been a single accident all winter.
In the event your car does crack the ice, though, it tends to sink slowly enough to allow you to scramble out.
With the onset of spring, the ice roads' days are numbered. This year they remained open until the end of March.
But some islanders continue to drive over the melting surface of the sea even after the official roads are closed. I hope they keep their seatbelts unbuckled.
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