One of Pakistan's deadliest road accidents this year unfolded on a mountain highway on Friday, when a long-distance bus went off the road and fell into a ravine.

The crash

The bus was traveling the long route from Quetta, the capital of Balochistan, toward Peshawar in the country's northwest when it lost control in the Sherani district, near where Balochistan meets Khyber Pakhtunkhwa province, Al Jazeera reported. It plunged into a deep, rocky ravine in a remote, mountainous stretch. At least 40 people were killed and several others injured, Dawn reported, citing rescue officials.

A local police official said speeding was a likely cause, though authorities said a formal investigation would determine what happened. The bus did not collide with another vehicle; it ran off the road on its own.

An overcrowded bus

Officials said the bus had become overcrowded after taking on additional passengers whose own vehicle had broken down earlier on the route — a common practice on Pakistan's long intercity runs. The remote terrain slowed the response, and rescue teams worked to reach the wreckage and move the injured to hospitals in the nearest towns.

A recurring toll

Deadly road crashes are distressingly frequent in Pakistan, where long-haul buses and trucks share mountainous, sometimes poorly maintained highways, and where speeding, overloading and uneven enforcement of traffic laws are persistent problems. Provincial officials said they had ordered an inquiry into Friday's crash and pledged measures to improve road safety — the same promise that tends to follow each of these disasters.

For the families waiting for news along the Quetta–Peshawar corridor, those pledges will mean little this weekend. A routine journey between two cities ended, once again, at the bottom of a ravine.