The Caldecott Tunnel is an east-west highway tunnel through the Berkeley Hills between Oakland and Orinda, California. Its four bores carry California State Route 24, named after Thomas E. Caldecott, former mayor of Berkeley, it opened in 1937 as a two-bore tunnel. The third bore opened in 1964 and the bore in 2013. Currently, the two oldest bores carry eastbound traffic and the two newest bores carry westbound traffic, the east-west tunnel is signed as a part of State Route 24 and connects Oakland to central Contra Costa County. It is named after Thomas E. Caldecott, from 1930–1932, member of the Alameda County Board of Supervisors 1933-1945, and president of Joint Highway District 13, Bore 1 and Bore 2 were completed in 1937 and are 3,610 feet in length. Both carry two lanes each of eastbound traffic, Bore 3, completed in 1964, is 3,771 feet in length. Bore 4, completed in 2013, is 3,389 feet in length, bores 3 and 4 carry two lanes each of westbound traffic. The active Hayward Fault runs just west of the portals of the tunnel. In the 19th century, traffic over the Berkeley Hills in this area went up Harwood Canyon, the road leading up the canyon from the west was initially called Harwoods Road, later changed to Telegraph Road, and finally, Claremont. The road on the side of the hills was, and remains. An inn and stage stop called the Summit House once existed at the summit. The idea of a tunnel through the hills began as early as 1860, in that year, the idea was proposed and rejected by the citizens of Alameda and Contra Costa Counties. The proposed tunnel would be only some 500 feet long and would have its outlet in the San Pablo Creek watershed with a road leading into Lafayette, a franchise was granted to a group of developers who passed the franchise onto another group. The proposal languished until the turn of the century, in 1903 a tunnel was finally built above the present location of the Caldecott Tunnel, in the next canyon south of Claremont Canyon. This tunnel was approached by a new road dubbed Tunnel Road which started at the top of Ashby Avenue in Berkeley and this tunnel was known as the Kennedy Tunnel, the Inter-County Tunnel or the Broadway tunnel. The tunnel was very narrow and arched, such that two tall buggies could not pass each other, a system of lighting a small fire with a newspaper was used to control this one-way traffic. The tunnel height was increased in 1915 by 3 feet to accommodate larger vehicles, when the new Caldecott tunnel was completed, the Kennedy tunnel was used mostly by pedestrians until it was sealed in 1947. In 1929, construction of the first two bores of the Caldecott Tunnel began
The Caldecott Tunnel, western end, before the construction of the fourth bore
The Caldecott Tunnel prior to the construction of the fourth bore as seen from the western end. From left to right, Bores 3, 2, 1.