The Bridge of Gallegos belongs to the town of Gallegos (just up the road). It originally dated from the 13th century but was destroyed in 1934 during the run up to the start of the Civil War; this was a common fate for many other bridges along the way, a deliberate effort meant to slow the enemy.
If you chose to stay on the road, remember that drivers expect you to be on the trail.
After crossing the bridge, continue along the road. It will take you uphill and straight through town. The arrows at the end of town turn right into the forested countryside. This is officially the camino, but on very wet days it is very muddy and it is just as easy to stay on the road into Escamplero.