Drivers are saying farewell to a half-century-old ritual in their trips to and from The 925 from Oakland and San Francisco.
With the new, $420 million fourth bore of the Caldecott Tunnel open — Caltrans opened it before dawn Saturday — four lanes of traffic are flowing in both directions for the first time. That ends the familiar “4/2″ traffic pattern that started when the Caldecott’s third bore opened in 1964. Here’s how Caltrans describes its routine of reversing traffic through what used to be the tunnel’s middle bore:
During the week, the middle bore of the Caldecott is reversed sometime between 2:00 a.m. and 5:00 a.m. to favor westbound traffic, and then switched again sometime between 11:30 a.m. and noon to favor eastbound traffic. Ballgames, concerts and other events make balancing weekend traffic through the tunnel very difficult. It is not uncommon to reverse the middle bore six times on a Saturday or Sunday.
The new fourth bore is taller and wider than the earlier bores, complete with a shoulder lane, is more brightly lit and features improved ventilation. Caltrans says that like the new eastern span of the Bay Bridge, the new bore is designed to be a “regional lifeline structure.” The Hayward Fault crosses Highway 24 just west of the tunnel’s Oakland portal, and the bore “is designed to reopen to emergency traffic within 72 hours of a major earthquake.”
A brief timeline of the Caldecott Tunnel and its Oakland Hills predecessors, by way of Caltrans. The original impetus behind the tunnel project was to make it easier to get from East Bay shore communities to Contra Costa County. The old way, still open if you care to drive it, was to go up the relatively precipitous slopes of Claremont Canyon from Oakland, cross a saddle of the Oakland Hills, then descend toward Orinda via Fish Ranch Road.
- Late 1870s: Work begins on the tunnel through hills from the Kennedy Toll Road but is abandoned after just 300 feet are excavated between Oakland Hills and Orinda. The toll road followed the route of the current Tunnel Road up to a portal which today marks the beginning of Skyline Drive.
- 1903: Broadway Tunnel, also known as Kennedy Tunnel and the Inter-County Tunnel. Says Caltrans: “The Broadway Tunnel was located about 220 feet above the current Caldecott Tunnel and 320 feet below the summit. It was 1,040 feet long and 17 feet wide and built with timber supports. Long, dark and narrow, the tunnel could only accommodate one-way traffic. Drivers on either side would ignite rolled-up newspapers to signal travelers on the other side to wait for them to pass through.”
- 1915: Broadway Tunnel widened to accommodate cars and trucks (and two-way traffic). Structure was subject to frequent leakage and landslides at either end, especially during rainy season.
- 1934: Work on the twin-bore “Broadway Low-Level Tunnel” begins.
- 1937: Broadway Low-Level Tunnel opens (13 months after opening of Bay Bridge and a little more than six months after opening of Golden Gate Bridge).
- 1960: Tunnel renamed after Thomas Caldecott, former mayor of Berkeley and public transportation official. Work begins on third bore.
- 1964: Third bore completed.
- 2010: Construction on fourth bore begin.
- Nov. 16, 2013: Fourth bore opens.