Explanation:

The Grand Trunk Road is one of the of South Asia's oldest and longest major roads. The road, often called as the "Gernaili Sadak" (the Generals' Road) and Sadak-e-Azam ('The Grand Road') covers a distance of over 2,500 kilometres (1,600 mi). It was built by Sher Shah Suri. During the British rulers of colonial India, the road was renamed as the Grand Trunk Road. 
This busy asphalted road still forms a vital link for trade and communication for the social strata that live along this region. The Grand Trunk Road, built by Sher Shah Suri, a ruler of the Indian sub continent in the 16th century AD, starts in Kabul, Afghanistan. The road continues to Pakistan near Peshawar through the famous Khyber Pass. This famous international mountain pass, at an elevation of 1,070 m (3,510 ft) above the sea level, is one of the oldest known passes in the world, and connects Afghanistan and Pakistan, cutting through the northeastern part of the Spin Ghar mountains.
After this mountain pass, the Grand Trunk Road arrives to the suburbs of Taxila, goes down to Lahore and crosses into India at Wahgha. After 2500km, the road ends at Kolkata. The road was built as a dirt track, but in the sixteenth century the Mughal emperors paved it. Nowadays the road is still by far the busiest, wildest road in areas that are now part of Afghanistan, Pakistan and India. During the British rulers of colonial India, the road was renamed as the Grand Trunk Road. 'GT', as it's often called, was built about 500 years ago to connect the east and western regions of the Indian subcontinent. Rudyard Kipling called it 'a river of life', but for the modern driver it's a nightmare. The 1,550 mile road is full of trucks and rattling buses manned by drivers without much respect for their lives - or yours. And then there's the cyclists, the pedestrians, the salesmen, the ox carts, the cows, the buffalos...
Over the years, it has functioned both as a major trade route and as a convenient right-of-way for invading armies. GT is considered dangerous not because of risky heights or disheartening road conditions, but because of the traffic congestion. You mustn't be surprised when your car gets into a traffic jam, created by dromedaries using one of the lanes. Trucks, buses, bicycles, pedestrians, and animals have turned parts of this heavily-used road into a major headache. If you’re planning to drive here, you’ll want to be as alert as possible.