The BBC's Andrew Whitehead, who is writing a book about the origins of the Kashmir conflict, has travelled along the road on both sides of the ceasefire line.
Here he looks back on its history ahead of Thursday's historic first bus journeys across the divided territory since partition in 1947.
Roadwork is under way to prepare for a new Kashmir bus service
Look at a map of the Kashmir valley. The river Jhelum runs like a fine blue thread through all the main cities.
It passes through Anantnag, moves north to the summer capital of Indian-administered Kashmir, Srinagar, then on to Baramulla where the valley narrows before tumbling across into Pakistan's part of Kashmir: past the city of Muzaffarabad, it turns south towards the plains of Punjab.
The road that runs alongside the Jhelum was once the main means of reaching the Kashmir valley.
In 1947, the year that India and Pakistan gained independence, it was the only year-round road into Srinagar.
All the others went over high mountain passes and were blocked by snow and landslips every winter.
In Muzaffarabad, the valley road is still known as the Srinagar road - though no one has been able to travel along it to the other half of divided Kashmir for decades.
Up the valley road in October 1947, thousands of pro-Pakistan tribal forces staged an invasion of Kashmir, reaching as far as the outskirts of Srinagar.
An airlift of Indian troops pushed the raiders back down the Jhelum valley.
The ceasefire that ended that first war over Kashmir led to what amounted to a partition of the region which snapped the valley road in two. And it's been closed more-or-less ever since.
The road was developed only about 100 years ago. Before then, reaching Kashmir was no easy task.
A Christian missionary who made the journey in 1890 set out from the city of Rawalpindi on a horse-drawn cart and took three days to reach Baramulla.
From there, the journey to Srinagar - now a little over an hour by road - took him another three days by boat.
As soon as the road was improved, it became the valley's lifeline.
When the Kashmir crisis first erupted, a British diplomat who made the bus journey through Muzaffarabad to Srinagar saw from his window armed bands of marauders.
"I think the bus on which I travelled was the last one to go through before the tribesmen who invaded Kashmir cut that road," he told his superiors.
The date of the journey - 21 October, 1947.
Call to prayer
"The valley of Kashmir is totally cut off from the rest of the world," reported India's Hindustan Times newspaper a few days later.
Pakistani Kashmiris queue in Muzaffarabad for a bus permit
The closure of the Jhelum valley road meant the dislocation of telegram and postal services, as well as the severing of fuel and food supplies.
When I travelled along the highway a few years ago, the Pakistan army escorted me to their base at Chakothi from where I could wave to Indian soldiers just across the Line of Control.
A few days later, I was looking down on Chakothi from an Indian army vantage point, so close that I could hear the call to prayer at Chakothi's mosque.
Traversing that tiny distance the long way round had taken me 72 hours - with three flights and two arduous road journeys.
The renewed bus service that has recently been agreed between India and Pakistan is a first step towards reopening what was once Kashmir's main commercial artery - though initially passengers will have to dismount and walk across the Line of Control.
Already, the fruit growers in Indian-administered Kashmir, whose apples take three days to reach Delhi, are musing about getting their goods to much closer markets in Pakistan.
If trade is allowed across the ceasefire line one day, Indian-administered Kashmir's orchards will be just six hours from Rawalpindi.