Section 6 of the TransAmerica Trail follows a 15-mile stretch of I-80 between Sinclair and Walcott, then turns south. The highway has heavy traffic, but cyclists can use the wide shoulder. The hilly basin called North Park contains the headwaters of the North Platte River, and from this point south to Canon City, riders traverse high-elevation country. Because of this altitude, some cyclists may experience headaches, insomnia, or shortness of breath, but most have approached this area gradually, from lower elevations, acclimatizing their bodies. As the trail approaches the Summit County area, traffic increases. The recreational facilities here attract many weekenders and vacationers from the more densely populated eastern slope of the Rockies. Around Frisco and Breckenridge, the route intersects with the Great Parks South Trail and the Great Divide Mountain Bike Trail. After Breckenridge, the South Park section begins with a moderately difficult climb on Hoosier P.