From the northern Afghan city of Mazar-e Sharif to the Uzbek border, the land runs flat with barely a hillock to block the way. It is perfect terrain for building a railway

says Afghanistan’s First New Railroad On Track, an 14 October 2010 by Charles Recknagel at Radio Free Europe/Radio Liberty.

There are details of construction and security on the new line from the Uzbek border to near Mazar-i-Sharif:

Currently, the railroad is guarded by a force of 500 police. The headquarters of the force is a small, windswept outpost halfway between Mazar-e Sharif and the Afghan border crossing of Hairaton, where the new rail line starts.

There is also a video showing construction work. This feature a twin-unit locomotive (a 2TE10?) in action at 55 sec, and then a smaller blue locomotive, both presumably belonging to Uzbek state railway UTY.