The south end of State Route 13 is unconstructed, extending 4.5 miles (7.2 km) beyond I-580 to SR 61 near the Oakland International Airport.

A very short piece at the north end has also not been built, extending west into the San Francisco Bay to the unconstructed SR 61 freeway.

A 21.8-mile (35.1 km) extension of State Route 14 from the Newhall Pass interchange with I-5 south to SR 1 northwest of Santa Monica was once proposed as the Reseda Freeway.

The eastern segment of State Route 36, stretching 17.0 miles (27.4 km) from SR 139 north of Susanville east to US 395 near Termo, was unconstructed until it was deleted from the legislative definition in 1998.

A locally maintained traversable route is Point Reyes-Petaluma Road and Novato Boulevard, but Caltrans has no plans to take it over.

11.4 miles (18.3 km) of State Route 39 are unconstructed, from Harbor Boulevard and Whittier Avenue in La Habra north to I-10 in Azusa.

However, Section 339(c) of the California Streets and Highways Code designates Harbor Boulevard and Azusa Avenue to be on the corridor between the two existing segments.

Caltrans has no plans for the remainder of the legislated route, stretching 8.6 miles (13.8 km) north from SR 91 to I-10 near downtown Los Angeles.

[2] The eastern end of State Route 74 from SR 111 in Palm Desert north 5.5 miles (8.9 km) to I-10 was unconstructed until it was relinquished and deleted from the legislative definition in 2013.

State Route 102 is a 37.5-mile (60.4 km) unconstructed freeway that would generally parallel I-80, beginning at I-5 near SR 99 north of Sacramento and heading east across I-80 and northeast to I-80 near Auburn.

A 21.5-mile (34.6 km) extension of State Route 108 is unconstructed, from its present west end at SR 132 in Modesto southwest to I-5 near Crows Landing.

A 10.5-mile (16.9 km) eastern segment of State Route 118 is unconstructed, running from I-210 near Sunland east to proposed SR 249 north of La Cañada Flintridge.

A locally maintained traversable route is along Pearblossom Highway, SR 138, and 50th Street East, but Caltrans has no plans to take it over.

The easternmost 10.4-mile (16.7 km) portion of State Route 128 is unconstructed, connecting I-505 near Winters (the current end) with SR 113 near Davis.

The 2002 Traversable Highways Report indicates that this segment will be considered for assumption of maintenance after a two-mile section of Russell Boulevard just east of I-505 is reconstructed.

A section of State Route 130 is unconstructed, stretching 24.8 miles from the present end at the Stanislaus County Line east to SR 33 near Patterson.

A proposed freeway path west of San Antonio Valley Road bypassing Mount Hamilton from either to the north toward State Route 237 or to the south toward San Jose's Evergreen district to I-5 was planned but feasibility of the project came into question, however, as constructing a freeway over the Diablo Range near three of its highest peaks (Mount Hamilton included) and across the Calaveras Fault would have been very difficult.

State Route 157, which was proposed from I-805 near Ocean View Boulevard in San Diego to SR 125 near Sweetwater Reservoir, was unconstructed until it was deleted in 1994.

The section of State Route 170 that was supposed to be the Laurel Canyon Freeway, which would have run from the Los Angeles International Airport to the San Fernando Valley via the Santa Monica Mountains, was unconstructed until it was deleted from the legislative definition in 2015.

The central portion of State Route 190 is unconstructed, stretching 43.0 miles (69.2 km) from Quaking Aspen in the Sequoia National Forest to US 395 at Olancha.

A 5.0-mile (8.0 km) western extension of State Route 217 is unconstructed, leading from the present end at the University of California at Santa Barbara northwest to US 101.

The southern end of State Route 227 is unconstructed, stretching 1.7 miles (2.7 km) from US 101 in Arroyo Grande to SR 1 east of Oceano.

A northern extension of State Route 238 is unconstructed, stretching west 1.6 miles (2.6 km) from the end of I-238 at I-880 to proposed SR 61 near San Lorenzo.

Then after a series of lawsuits and appeals, the freeway plan was canceled in 2003 and Caltrans sold off the property it had acquired in the name of eminent domain along the proposed route.

Caltrans has identified Mountain House Road and Byron Highway (CR J4) as a traversable route, but has no plans to maintain it.

The section from Oso Parkway to Cow Camp Road near SR 74 is currently under construction while the remainder of the extension is still under discussion.

If built, the highway was probably going to be called the "Point Reyes Freeway"; extra flyover ramps at the Sir Francis Drake Boulevard-U.S. 101 interchange suggest this.

The majority of State Route 281 is unconstructed, stretching 14.0 miles (22.5 km) from the current end at Clear Lake northwest to SR 29 south of Lakeport.

A locally maintained traversable route is along Sneath Lane, Skyline Blvd and Sharp Park Road, but Caltrans has no plans to take it over.

It was proposed as the Golden Gate Freeway in the mid 1950s but was ultimately canceled due to the 1989 Loma Prieta earthquake as well as local opposition.