Train track was laid down to connect Dubai and Abu Dhabi in a landmark moment for the two cities.
The work is the latest development in Etihad Rail's freight project, which will eventually connect all seven emirates and the east coast to the Saudi Arabian border.
Etihad Rail chairman Sheikh Theyab bin Mohamed bin Zayed visited the site as the country's latest megaproject, which ferries heavy industrial materials, took shape.
Work has gathered pace at the Seih Shuaib site near the border of the two largest emirates.
He reviewed the progress made during a 10km trip aboard an inspection train.
The journey started from the operations centre at Seih Shuaib and moved in both directions towards Abu Dhabi and Dubai up to Al Maha Forest, where Sheikh Theyab was briefed on measures being put in place to protect wildlife and natural habitats through the construction of bridges, canals and animal crossings.
The first stage of Etihad Rail – linking the gasfields at Shah and Habshan to Ruwais – is already in operation.
Now the second stage of the large-scale scheme – stretching about 1,000km from Ghuweifat on the border with Saudi Arabia to Fujairah on the UAE’s east coast – is advancing rapidly.
Etihad Rail also said in January it started construction of the 139km stretch connecting the existing line at Ruwais to Ghuweifat. About 59 per cent of the project has been completed, it said.
Etihad Rail was created in 2009. Freight is the focus, but its original mandate included a potential passenger element.
It is also envisaged that the UAE lines could form part of a wider GCC rail network.
Sheikh Theyab, also chairman of Abu Dhabi Crown Prince's Court, thanked UAE leaders for their support of the project and all local and federal organisations involved in its development.
He said the rail network is designed to provide a safe, reliable and integrated mode of transport and will support economic growth by connecting the country's main ports with industrial, manufacturing and residential centres.