NM 159 from milepost 4 to milepost 25 (Willow Creek Campground). STEEP GRADES AND NUMEROUS TIGHT TURNS. Trucks without retarder brakes and/or longer than 46 feet in length are PROHIBITED on this section of NM 159. Trucks longer than 30 feet are highly encouraged to utilize a pilot vehicle. Consider using an alternate route - US 180 to NM 12 to NM 435 (NF-141). THIS IS A PERMANENT ALERT.