California State Highway 86 is a north-south highway in the southeastern desert region of Southern California. It links the Coachella Valley starting in Indio where it is co-signed with California State Highway 111 for a short distance before splitting in Coachella and continuing southward along the western shoreline of the Salton Sea to the Imperial Valley. It rejoins 111 in Heber before terminating in Calexico at the Mexican border.

Unusual "86S" state highway sign near an on-ramp on Dillon Road in Coachella

In the late 20th century, 86 had a rather notorious reputation for frequent and often fatal collisions. For much of its length, especially between the southern tip of the Coachella Valley to the Imperial County line, 86 was a two-lane road with easy access from rural side roads. A driver trying to pass might find himself headed straight for the side of another vehicle pulling out from one of the side roads. This reputation earned 86 the nickname, "Blood Alley."

Originally a part of U.S. Highway 99, California's main north-south highway before 99's decommissioning between 1964 and 1968, the northern end of 86 was widened and rerouted through the new and rather unusually numbered "86S Expressway" soon after the signing of the NAFTA agreement, making Highway 86 a four- or six-lane highway for most of its length. Since it is easier to enter California from the Imperial Valley rather than through San Diego, 86 sees a great deal of truck traffic to and from Mexico, earning it still another nickname, "The NAFTA Highway."

One of the world's most important innovations in highway safety owes its existence to 86. Doctor June McCarroll worked as a nurse for the Southern Pacific Railroad soon after US 99 opened in the 1920s as one of the first national highway arteries. Her office in Coachella bordered on the new highway and was the scene of many an accident even in the highway's earliest days, primarily head-on collisions caused by drivers drifting into oncoming traffic.

Nurse McCarroll had the simple yet revolutionary idea of painting a stripe down the middle of the highway, which effectively kept the two lanes of traffic separated. This was the first ever highway marking of its kind and was soon adopted worldwide. A stretch of nearby Interstate 10 has been named in her honor.