History of the Caldecott

In the 1880s, a stagecoach trip from Lafayette to Oakland took more than two hours. The most formidable part of the journey was traveling over the steep, twisting roads that wound through the Berkeley Hills, separating Alameda and Contra Costa counties. Accidents were frequent – sometimes fatal – when horse-drawn carriages careened out of control on the steep slopes, crashing into trees or rocks or colliding with other carriages.

The Kennedy Toll Road

A tunnel had been considered as far back as the 1860s, but no progress was made towards building one until the late 1870s when the Oakland and Contra Costa Tunnel Company built the Kennedy Toll Road. One-hundred feet of tunnel were dug on the Contra Costa side and 200 feet were excavated from the Oakland side before the company ran out of money.

For the next 30 years, travelers either contended with the difficult road over the saddle of the Berkeley Hills or took the long way around through Richmond.

In the meantime, merchants in Oakland continued to complain that they were losing business to San Francisco or Martinez, which were farther away as the crow flies, but easier to access because of the local railroads.

The Old Broadway Tunnel

The dream of a tunnel was revived in the 1890s when money from the two counties and funding from private citizens financed a new tunnel.

After decades of planning and false starts, the new tunnel opened in 1903. As for the name of the tunnel, it depended on whom you talked to or which historical account you read. Some called it the Broadway Tunnel for the road that accessed it. Others referred to it as the Kennedy Tunnel for the old toll road and the local farm near the west portal. Since its abandonment, it is usually referred to as the "Old Broadway Tunnel".Old_Broadway_Tunnel_r2

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.

Enter at Your Own Risk

By 1915, the Broadway Tunnel was widened to accommodate automobiles and trucks. But it was never a very wide tunnel and trucking was hindered by the steep approaches.

Water seepage, particularly in the winter months, plagued the tunnel. In December 1920, the tunnel was closed for ten days to fix a leak in the tunnel roof.

In November 1926, heavy mudslides fell onto the highway at the east end of the tunnel, engulfing a car but not injuring its occupants. Afterwards, men were stationed at both entrances to warn motorists that they could use the tunnel, but at their own risk.

According to the Oakland Tribune:

Repair work ordered spasmodically always resulted in the tunnel being declared in "good working repair," and in August 1927, Oakland City Engineer George Randle said "the tunnel is quite safe."

"The fact that it is somewhat out of line need not alarm anybody," he said, admitting there was "some movement" to the posts, which by 1927 stood on the concrete flooring.

Eventually, the Old Broadway Tunnel was replaced by the Caldecott Tunnel. The Old Broadway Tunnel, with sections possibly collapsed, had its portals sealed off for public safety.

The Twin Bores

Alameda and Contra Costa counties, as well as the City of Oakland, formed a joint commission in 1926 to study the feasibility of relocating the passage to a lower level. In 1929, the two counties formed Joint Highway District No. 13, with the specific purpose of building the Broadway Low Level Tunnel, which featured two bores (one for each direction of traffic).

The Players

Early planning for the project was supervised by the chief engineer of the highway district, George Addison Posey. (The Posey Tube connecting Oakland and Alameda is named after him.) His assistant, Wallace B. Boggs, facilitated the final design after Posey's death. Henry H. Myers, who was the Alameda County Architect at the time, served as the project architect. Among other aspects of the tunnel, Myers designed the Art Deco relief on the portals. Myers would go on to gain fame as the architect of many commercial buildings in San Francisco.

One of the biggest boosters of the project was a former Alameda County supervisor and president of the Joint Highway District named Thomas Caldecott. The current tunnel is named in his honor.


Construction of the Broadway Low Level Tunnel began in 1934. However, the contractor, the Six-Man Company, was unable to complete the construction stages in a timely manner. With 68 percent of the project complete, the contract was broken down into smaller contracts and awarded to individual companies to complete the project.

An Era of Great Public Works

The Broadway Low Level Tunnel was opened to traffic on December 5, 1937. Ceremonies were held on the Oakland side replete with fireworks, Army planes and pigeons flying overhead. The governor was among the many politicians to give a speech. A final ceremony was held on the Contra Costa side, while traffic lined up for miles for a maiden voyage through the new tunnel.

This was an era of great public works in the Bay Area. The completion of the Broadway Low Level Tunnel nearly coincided with the opening of the Bay Bridge, making possible an easy commute by automobile from Contra Costa to San Francisco and back.

The Broadway Low Level Tunnel was an impressive feat of engineering; the two bores are still in use today. Each of the twin bores measures 3,610 feet long and nearly 27 feet wide. Two 11-foot lanes are contained in each bore.

The Third Bore

By the late 1950s, the Division of Highways improved State Highway 75 – the approach to the tunnel – upgrading it to a modern freeway. With Contra Costa County accessible by freeway, it quickly changed from a farming community and urban getaway into a major suburb.

The Division of Highways purchased sufficient right-of-way to the north of the existing twin bores to build another pair of bores. Given the traffic counts and the expense – even in those days – of tunnel construction, the construction of two additional bores would have been seen as unnecessary and extravagant.

However, with the traffic count exceeding 50,000 vehicles per day, the state embarked on a project to build a third bore at the Caldecott Tunnel.

Easing Congestion

The project broke ground in 1960 and was completed by October 1964. When the third bore was opened, the other bores were closed one at a time for maintenance, including the installation of a continuous row of fluorescent lights. Eventually the new third bore made it possible to reverse the traffic flow of the middle bore, providing four lanes to accommodate the heavier commute-direction traffic.

The third bore also brought new technology to the tunnel with the installation of the "pop-up" lane control. Plastic lane delineators are set in tubes within the pavement. With the touch of a button, the delineators pop up from the pavement, closing the middle bore to one direction of travel, while opening it to another.

Challenges of Weekend Traffic

In addition to the reverse commute, weekend traffic is notoriously difficult to predict. 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.

As novel as it was in the 1960s and as helpful as it has been throughout the years, the pop-up system still requires a lot of manpower to implement. While the pop-up system eliminates the need to set down individual cones to separate traffic, Caltrans maintenance workers must move traffic out of the closing lanes, lest vehicles get caught on the wrong side of the pop-up delineators.


With the passage of Regional Measure 2 in 2004 and Contra Costa Measure J in the same year, a regional and county funding source was found to finance the Fourth Bore Project. Proposition 1B, passed by state voters in 2006, allowed the state to issue bonds to fund large-scale construction projects like the Caldecott Tunnel Fourth Bore Project. However, during the financial crisis of 2008/09, the financial markets became so illiquid that bonds could not be easily sold and the start date of the project was jeopardized. Fortunately, federal and state leaders were able to secure federal stimulus money to replace much of the bond money and prevent project delays.