The Greenhorn Cutoff was actually an alternate route around Carlin Canyon that allowed emigrants to bypass the four crossings of the Humboldt River required on the main California Trail. The crossings were especially difficult and dangerous during high-water years. The cutoff began near Hunter Exit 292 on I-80 and wound north around Carlin Canyon before turning south alongside Dry Susie Creek to reconnect with the main California Trail.
Contrary to its derisive name, the Greenhorn Cutoff was actually several miles longer than the main trail and had its disadvantages, including the fact it was more mountainous and drier than the main trail. Additionally, the Carlin Canyon crossings were not actually very bad most years.
The locations in the map below show all the Trails West T-markers between the east and west ends of the Greenhorn Cutoff. NOTE: Many of these markers require 4-wheel drive to access.