ROBINSON TWP., MI (WHTC) - A couple of dirt bike drivers on land east of Grand Haven collided on Saturday afternoon, sending both of them to area hospitals. Just after 2 PM, Ottawa County Sheriff’s Sergeant Brian Buter and fellow deputies were called to the site off of 144^th Avenue between Green and Lincoln Streets in Robinson Township, where 15-year-old Jordan Bradley and 25-year-old Peter Pierson were riding their machines. After an unknown amount of time, one of the bikes crossed into the path of the other, causing a collision that threw both riders off of their machines, although it wasn’t immediately known which one rode in front of the other. Bradley was eventually flown to Spectrum-Butterworth Hospital in critical condition; Pierson went by ambulance to that same Grand Rapids-based medical center in serious condition. The crash remains under investigation.