traffic lanes, one shoulder, and one shoulder, ventilation, air and traffic monitoring systems, traffic lights, and electronic message boards. There are emergency exits to the third bore. When the fourth bore was opened to traffic, the need for the daily traffic reversal was eliminated; two bores (four lanes) serve each direction at all times, although individual bores may be closed during periods of light use for maintenance purposes. Weather phenomena Weather conditions can vary greatly from one end of the tunnel to the other. In summer, for example, motorists may enter the tunnel from the east where it is sunny and warm, and emerge on the west end into fog and cold. In winter, during spells of inland tule fog, the reverse can occur. In popular culture The Caldecott Tunnel appears in many of Rick Riordan's books, acting as an entrance to Camp Jupiter. In The Tyrant's Tomb, it is the site of the final battle between the protagonists Apollo and Frank Zhang and the Roman emperors Commodus and Caligula. See also Berkeley Hills Tunnel — BART rail transit tunnel, running approximately parallel to, and north of, the Caldecott Tunnel. Solon, Mary; McCosker, Mary (2014). Building the Caldecott Tunnel. Images of America. Charleston, South Carolina: Arcadia Publishing. . References External links California Department of Transportation website on the Caldecott Improvement Project Construction Photo (1936) of the West Portal, Contra Costa Historical Society Aerial View (1936) Showing Old and New Tunnels, Contra Costa Historical Society Road tunnels in California Tunnels in the San Francisco Bay Area Berkeley Hills Buildings and structures in Oakland, California Transportation buildings and structures in Alameda County, California Orinda, California Transportation buildings and structures in Contra Costa County, California Transportation in Oakland, California Tunnels completed in 1937 Tunnels completed in 1964 1937 establishments in California Articles with WikiMiniAtlas displaying incorrectly; WMA not showing route