The best route into the park from the east or south is from Flagstaff. Take U.S. 180 northwest to the park's southern entrance and Grand Canyon Village. To go on to the North Rim, go north from Flagstaff on U.S. 89 to Bitter Springs, then take U.S. 89A to the junction of Highway 67 and travel south on the highway for about 40 mi. From the west on Interstate 40, the most direct route to the South Rim is on U.S. 180 and Highway 64.
The South Rim is open to car traffic year-round, though access to Hermits Rest is limited to shuttle buses from March through November. Parking is free once you pay the $25 park entrance fee, but it can be hard to find a spot. Try the large lot in front of the general store near Yavapai Lodge or the Maswik Transportation Center lot. If you visit from October through April, traffic will be lighter parking less of a problem.
There are three free shuttle routes in the Grand Canyon: The Hermits Rest Route operates March through November, between Grand Canyon Village and Hermits Rest. The Village Route operates year-round in the village area; it provides the easiest access to the Canyon View Information Center. The Kaibab Trail Route goes from Canyon View Information Center to Yaki Point, including a stop at the South Kaibab Trailhead. In summer, South Rim roads are congested, and it's easier, and sometimes required, to park your car and take the free shuttle. Running from one hour before sunrise until one hour after sunset, shuttles arrive every 15 to 30 minutes. The roughly 30 stops are clearly marked throughout the park.
The more remote North Rim is off limits during winter. From mid-October (or the first heavy snowfall) through mid-May, there are no services, and Highway 67 south of Jacob Lake is closed.