The value of this trail is not it's quality riding. It's value is in giving one access to all the riding on Bogd Uul without riding the crazy busy streets on UB. And this route gives you a rare legal crossing point on the railroad tracks for pedestrians (and bikes).
From the Kino Uildwer Bus Stop head south down the small dirt road into the ger district. It quickly connects up with the main artery dirt road that heads south through the ger district following along the flood canal. You can have some fun along here jumping off the canal embankment onto the dirt road. Follow this dirt road to the South Road (about 1/2 mile from the bus stop). Cross the south road and head about 0.1 mile to the railroad tracks. Cross the tracks through the two breaks in the fence. Go another 0.1 mile to the next paved road. Head west 200 yards, and then turn south through a guard gate onto a dirt road. The guard is friendly and will let you through. You again head south and follow the canal on the random dirt roads. Continue for about 1.1 miles until you reach the dike of the Tuul River. Ride the dike west about 2/3 mile until you reach Marshal Bridge. Head south again to cross the bridge about 1/3 mile, and you will reach the River Road and access to all the riding on Bogd Uul.