China's latest high-speed railway route is moving even closer to completion. The main track of the Beijing-Zhangjiakou Intercity Railway was finished on Wednesday.

Construction along the line, also known as the Jingzhang high-speed railway, began in early 2016. The railway will be in service by the end of the year.

It is China's latest mass transit milestone. Crews have finished track-laying and are currently paving the Jingzhang high-speed railway. After more than seven months of work, a ceremony was held at the entrance of Beijing's Tsinghua Garden Tunnel on Wednesday to mark the completion of work.

Ma Kanyan, chairman of Jingzhang company, said the construction began in March 2016, and now the main track-laying of the high-speed railway and Chongli Railway are officially over. This construction lays a solid foundation for joint commissioning and testing this September, and a scheduled opening by the end of this year.

It's the world's first ballasted track railway designed for trains traveling up to 350 kph. The 174-kilometer-long railway will cut train commuting time between Beijing and Zhangjiakou from more than three hours to less than one.

Experts say the breakthrough wasn't without challenges.

Huang Jianchao, senior engineer of China Railway Third Bureau, said some of the main lines are made up of long ramps, which were the biggest challenges. The track-laying underwent testing by smart robots, a first for China's high-speed railway.