The best way to see Grand Teton National Park is by car. Unlike Yellowstone's Grand Loop, Grand Teton's road system doesn't allow for easy tour-bus access to the major sights. Only a car will get you close to Jenny Lake, into the remote Gros Ventre Range on the east side of the valley, and to the top of Signal Mountain. You can stop at many points along the roads within the park for a hike or a view. Be extremely cautious in winter when whiteouts and ice are not uncommon. There are adequate road signs throughout the park, but a map is handy to have in the vehicle.
Jackson Hole’s main highway (U.S. 89/191) runs the entire length of the park, from Jackson to Yellowstone National Park's south entrance. (This highway is also called Route 26 south of Moran Junction and U.S. 287 north of Moran Junction.) This road is open all year from Jackson to Moran Junction and north to Flagg Ranch, 2 miles south of Yellowstone. Depending on traffic, the southern (Moose) entrance to Grand Teton is about 15 minutes from downtown Jackson via the highway. Coming from the opposite direction on the same road, the northern boundary of the park is about 15 minutes south of Yellowstone National Park. Also open year-round, U.S. 26/287 runs east from Dubois over Togwotee Pass to the Moran entrance station, a drive of about one hour.
Two back-road entrances to Grand Teton require high-clearance vehicles. Both are closed by snow from November through mid-May and can be heavily rutted through June. Moose-Wilson Road (Wyoming Highway 390) starts at Route 22 in Wilson (5 miles west of Jackson) and travels 7 miles north past Teton Village to the Granite Canyon entrance station. Of the 9 miles from here to Moose, 1½ are gravel. It's closed to large trucks, trailers, and RVs. Even rougher is 60-mile Grassy Lake Road, which heads east from Route 32 in Ashton, Idaho, through Targhee National Forest. It connects with U.S. 89/287 in the John D. Rockefeller Jr. Memorial Parkway, sandwiched between Grand Teton and Yellowstone.