After meeting State Route 138 at Mount Anderson Junction south of Crestline, the expressway reverts to a two-lane mountain road.It meets two other highways, State Route 189 just east of Arrowhead Highlands and State Route 173 in Lake Arrowhead, before running over State Route 330 in Running Springs.
At its west junction with State Route 38 near the west corner of Big Bear Lake, Route 18 jogs across a dam and travels along the south shore of Big Bear Lake.
After going through the City of Big Bear Lake, it overlaps with SR 38 and moves from the south to the north side of Bear Valley east of both Big Bear Lake and the Big Bear City airport before it descends from the mountains to the desert on the northerly side of the mountains, first heading northeast, briefly north, and then northwest.
SR 18 is part of the California Freeway and Expressway System, SR 18 from SR 138 at Crestline to SR 38 at the westernmost point of Big Bear Lake, and the SR 18/38 overlap in the City of Big Bear Lake, are designated as part of the Rim of the World Scenic Byway, a National Forest Scenic Byway.
Much of SR 18 has been signed since 1917, with the portion north of Big Bear Lake dating from 1933.
A proposal to construct a rail link between Southern California and Las Vegas has taken on new life.
Brightline, the Florida-based company that recently completed construction of a passenger rail line between West Palm Beach and Miami, has agreed to acquire Xpress West, a long-planned high-speed rail project seeking to connect the Greater Los Angeles area with the Las Vegas Strip.
SR 18 at this point follows the cities on the north face of the San Bernardino Mountains in the Mojave Desert: In Lucerne Valley, it turns west for 21 miles with SR 247 1/8th of a mile north of the bend.
It goes past the east terminus of Bear Valley Road (a major Victor Valley area cutoff) outside of Apple Valley town limits as it becomes an expressway (Happy Trails Highway, given for the High Desert's residency and final resting place of the legendary singing cowboy, Roy Rogers) through Apple Valley and Victorville.
In 1964, SR 18 was rerouted from the northern side of Big Bear Lake to the southern side along the former routing of SR 38 and lost its Legislative Route 43 designation.
In 1984, the portion of SR 18 running concurrently with Interstate 15 in Victorville was removed from the legislative definition.
This represents a one-hour time savings when compared to an average drive between Victorville and Las Vegas, but still a slower trip than the roughly one-and-a-half-hour trip previously envisioned.