| State: | NM |
| Type: | SR |
| Route: | 4 |
| Maint: | NMDOT |
| Map Custom: | yes |
| Map Notes: | NM 4 highlighted in red |
| Length Mi: | 67.946 |
| Length Round: | 3 |
| Length Ref: | [1] |
| Tourist: | Part of Jemez Mountain Trail National Scenic Byway |
| Direction A: | West |
| Terminus A: | in San Ysidro |
| Direction B: | East |
| Terminus B: | north of White Rock |
| Counties: | Sandoval, Los Alamos, Santa Fe |
| Previous Type: | NM |
| Previous Route: | 3 |
| Next Type: | NM |
| Next Route: | 5 |
New Mexico State Road 4 (NM 4) is a 67.946adj=midNaNadj=mid state highway in Sandoval, Los Alamos, and Santa Fe counties in New Mexico, United States. It is significant as the main access route (in conjunction with NM 501 and NM 502) connecting the remote town of Los Alamos, Los Alamos National Laboratory, and Bandelier National Monument to other, more major highways in New Mexico.
NM 4's western terminus is in the small town of San Ysidro, at U.S Route 550. The route passes through Jemez Pueblo and Jemez Springs as it climbs steeply into the Jemez Mountains and Santa Fe National Forest, and skirts the southern boundary of Valles Caldera National Preserve. On the east side of the Jemez Mountains, it descends even more steeply, on a series of hairpin turns offering views into Frijoles Canyon in Bandelier National Monument, to a junction with NM 501 leading east into the town of Los Alamos. NM 4 itself continues past the main entrance to Bandelier and several Los Alamos National Laboratory sites, as well as the town of White Rock, to another junction with NM 502 east of Los Alamos, where the route ends. The continuation of NM 502 to Pojoaque was formerly designated as NM 4 as well.
In contrast to several other state highways in northern New Mexico, NM 4 is paved for its entire length. It is predominantly a 2-lane road, with passing lanes in several places in the mountains. A short section near White Rock was 4-lane until its reconstruction in 2012; now that stretch is 2 lanes with many left-turn turn lanes going to businesses and streets in White Rock. Speed limits on most of the highway are 50 or 55 miles per hour (mph), although the tight curves make it dangerous to maintain maximum speed in many sections. Speed limits are lower near and through the towns.
The coniferous forest traversed by NM 4 in its upper regions is prone to severe forest fires, several of which have burned up to the highway.[2] Unfortunately, the highway is too narrow to serve as an effective firebreak, and such devastating fires as the 1977 La Mesa Fire and 2000 Cerro Grande Fire, the most severe forest fire in the state's history, have jumped the road to destroy forests, and habitations, on both sides of the road—in the case of the Cerro Grande Fire, into the upper reaches of Frijoles Canyon, contributing significantly to the magnitude of the disaster caused by the fire.[3]
NM 4 forms the main artery of the Jemez Mountain Trail National Scenic Byway.[4] The Byway includes short excursions on New Mexico State Roads 502, 126, and 290. Notable points of interest on the NM 4 section of the Byway include: