/ California Bridges
When the San Francisco-Oakland Bay Bridge, commonly
known as the Bay Bridge, collected tolls in 1940, it cost a quarter to drive
across the San Francisco Bay from San Francisco to Oaklandd―pretty steep for that
time. But it was well worth the price to pay off a magnificent structure that
allowed automobiles and trucks to access two sides of the bay. Though the toll
fee started at 60¢ and was reduced to a quarter to compete with ferry boats, it
would eventually pay off the bridge funding bonds and a trip across the bridge
would be free. Over 60 years later, drivers paid $3 to cross the bridge in 2005
with expectations of fee increases. This vital toll bridge spanning the San Francisco Bay
and linking the California cities of Oakland and San Francisco in the United States
needed a facelift 60+ years after being built—but
nature made sure the job was done sooner rather than later. As you drive over
this bridge, you'll likely see construction zones and re-building efforts
predicted to last until 2012.
On the best of days, the bridge
experiences bottlenecks where drivers must stop or creep along at a
snail's pace. The Bay Bridge has become a key link in the
regional automobile and bus transportation network and is so heavily
used that major accidents can cause traffic jams for hours, even when
the accident scene is quickly cleared. Traffic on other bridges in the
area becomes extremely slow as drivers seek alternate paths to their
But the huge Loma Prieta
earthquake that rocked the bay area October 17, 1989, collapsed a
section of the Bay Bridge, causing closure for over one month.
Californians riveted to their televisions can't forget the video
repeated over and over again, showing a car perched on the edge of ledge
of a broken road, smack dab on the bridge in the middle of the San
Francisco Bay. The huge Loma Prieta earthquake measured 7.1 on the
Richter scale. There were 142 road closures as a result of the quake,
with It's San Francisco Bay Bridge and Cypress off-ramp structure of the
Dumbarton Bridge in Oakland taking the greatest hit. Only one death
occurred on the Bay Bridge as a result of the quake's aftermath.
The bridge consists of two major
segments connecting a central island, Yerba Buena Island, with each
shore. The western segment terminating in San Francisco consists of two
suspension bridges end-to-end with a central anchorage. The eastern span
terminating in Oakland consists of a truss causeway, five medium-span
truss bridges and a double-tower cantilever span, scheduled to be
replaced by an entirely new structure now under construction. The
original bridges were designed by Ralph Modjeski. The Bay Bridge opened
for traffic on November 12, 1936, six months before San Francisco's
other famous bridge, the Golden Gate.
The toll plaza on the Oakland side (for westbound traffic) has several
dedicated FasTrak lanes, and is followed by a set of metering lights.
Two bus-only lanes bypass the tolls and metering lights. Two other sets
of High Occupancy Vehicle (HOV) lanes end at the toll plaza. There are no metering lights for
eastbound traffic, though the number of lanes in the San Francisco
approach is structurally restricted, creating backups in this direction
during evening rush hour. During the morning rush hour, some of the Bay
Area's worst traffic congestion stretches from the Oakland approach onto
feeder highways, especially I-80 toward Richmond, California. Unlike the
Golden Gate Bridge, Bay Bridge is restricted to freeway traffic only; pedestrians, bicycles, and
other non-freeway vehicles are not allowed.
San Francisco, located at the mouth of the bay, was in a perfect
location to prosper during the California gold rush. Almost all goods
not produced locally arrived by ship. After the first transcontinental
railroad was completed in May 1869, the city found itself on the wrong
side of the bay, separated from the new rail link. The fear of many San
Franciscans was that the city would lose its position as the center of
trade. The concept of a bridge spanning the San Francisco Bay had been
considered since the gold rush days. Several newspaper articles during
the early 1870s discussed the idea. In early 1872 a "Bay Bridge
Committee" planned to construct a railroad bridge.
The 1.78-mile western span of the bridge between San Francisco and Yerba
Buena Island presented an enormous engineering challenge. The bay was up
to 100 feet deep in places and the soil required new
foundation-laying techniques. At the time of construction suspension
bridges could not be made with more than a pair of towers owing to
stability considerations, and a two tower span would be longer than
practical. The solution was to construct a massive concrete anchorage
halfway between San Francisco and the island and to build two complete
suspension bridges, one on either side of the central anchorage. Modern
cable-stayed bridges may have any number of towers and a modern
suspension span, the Chacao Channel bridge is under construction that
will have two main spans, made possible by the use of a rigid central
tower composed of two A frames.
The eastern span was an engineering feat as well. The crossing
from Yerba Buena Island to Oakland was spanned by a 10,176-foot
combination of double cantilever, five long-span through trusses and a
truss causeway, forming the longest bridge of its kind at the time, with
the cantilever portion being the most massive yet constructed.
Connecting the two halves of the bridge is Yerba Buena Tunnel measuring
76 feet wide, 56 feet high, and 1,700 feet long. It was the largest
diameter tunnel in the world. The enormous amount of rock and dirt
excavated from the tunnel was used in part to create Treasure Island.
Construction began on July 9, 1933 with much of the original bridge
built on treated wood piling from old growth Douglas Fir trees driven
through the soft mud to firmer bottom. (Construction of the Bay
Bridge began shortly after that of the Golden Gate Bridge but the Bay
Bridge was completed six months sooner.) The total cost of construction
for the bridge was $79.5 million. At completion, the bridge became the
longest suspended-deck bridge in the world and the longest cantilever
bridge in the world. Because it was in effect two bridges strung
together; the western spans were ranked the second and third largest
suspension bridges. Only the George Washington Bridge had a longer span
between towers. The bridge was opened to traffic on November 12, 1936.
When the bridge first opened, it carried U.S. Highways 40 and 50. This
was replaced by Interstate 80 in 1964. It now also carries traffic
moving up the peninsula from two major highways, US 101 and Interstate
280, and from the eastern side ultimately connects with State Highway 24
to central Contra Costa County and Interstate 880 from San Jose
(formerly State Highway 17), The bridge has become a key link in the
regional automobile and bus transportation network. It is so heavily
used that major accidents can cause traffic jams for several hours, even
when the accident scene is quickly cleared. A severe jam can in turn
cause traffic on other bridges in the area to become extremely slow as
drivers seek alternate paths to their destinations.
The original west approach to the bridge was at Fifth and Bryant
Streets, and this is still an entrance to and exit from the freeway,
which now continues as the James Lick Skyway. The 1958 reconstruction
work on the Bay Bridge also added exit and entrance ramps to the one-way
streets that flank the Transbay Terminal.
When the bridge first opened, the upper deck consisted of three lanes of
automobile traffic in each direction. The lower deck carried three lanes
of truck traffic and two streetcar tracks used by the Key
System. Automobile traffic increased dramatically in the ensuing decades
while the Key System declined, and in 1957 the bridge was reconfigured
with five lanes of westbound traffic on the upper deck and five lanes of
eastbound traffic on the lower deck. Trucks were allowed on both decks
and the railway was removed. It was necessary to lower the upper deck
where it passed through the tunnel and to correspondingly excavate the
lower portion so trucks
could clear the upper-deck portion of the Yerba Buena tunnel. This was done while the
bridge was in use by using a movable temporary span over the portion
being lowered. On the lower deck of the tunnel and its eastern viaduct
extension it was necessary to remove central supports, with each
transverse beam being doubled to take the load across all lanes. It was
also necessary to further reinforce each beam supporting the upper deck
throughout the entire span, modifications still visible to the traveler.
The series of lights adorning the suspension cables were added in 1987
as part of the bridge's 50th-anniversary celebration.
The entire bridge was fabricated using hot steel rivets, which are
impossible to heat treat. The rivets were replaced with heat-treated
high-strength locator nuts and bolts. Also, the majority of beams were
originally constructed of two plate I-beams joined with lattices of flat
strip or angle stock. These have all been reconstructed by replacing the
riveted lattice elements with bolted steel plate, converting the lattice
beams into box beams. This replacement included replacing large diagonal
beams joining the faces of the main towers, which now have an improved
appearance when viewed from certain angles. Diagonal box beams have been
added to each bay of the upper and lower decks of the western spans.
These add stiffness to reduce side-to-side motion during an earthquake
and reduce the probability of damage to the decking surfaces.
Engineering and economic analysis in 1999 suggested that a simple
replacement bridge would cost only a few hundred million dollars more
than a retrofit of the existing eastern span and that a replacement,
would have longer life span and would require less maintenance. After more than a decade of study, construction began
on a replacement for the cantilever portion of the bridge on January 29,
2002, with completion scheduled for 2012 at a cost of $6.3 billion.
The legal name of the bridge is The James "Sunny Jim" Rolph
Bridge, in honor of a former San Francisco mayor and governor of
California. The name is not widely
recognized and for all functional purposes has always been
the San Francisco-Oakland Bay Bridge.
CalTrans, the state highway transportation agency, maintains seven of
the eight San Francisco Bay Area bridges, excluding Golden Gate Bridge,
owned and maintained by the Golden Gate Bridge, Highway and
San Francisco-Oakland Bay Bridge has appeared in many films and novels.
In the movie, The Graduate, Dustin Hoffman drove on the top level of the
bridge, supposedly towards Berkeley; however, the top-level traffic goes
to the San Francisco side, not Berkeley and the East Bay. The bridge
also appeared in films such as Born to Kill, Vertigo, The End of the
World, George of the Jungle, Made in America, Basic Instinct, Sudden
Impact, Sister Act I & II, The Incredible Hulk, and Sid & Nancy.
The Bay Bridge Stats
Location: Interstate 80 between San Francisco and Alameda Counties.
Length: 23,000 ft (4.35 miles, 7 km)
Western suspension bridges
Length 9,260 ft (2,822 m)
Vertical clearance 220 ft (67 m)
Tower height 526 ft (160 m) from water level
Eastern cantilever bridge, truss bridges and truss causeway approaches:
Length: 10,176 ft (3,101 m)
Vertical clearance 191 ft (58 m)
Deepest bridge pier: 242 ft (74 m) below water level – 396 ft (120 m)
Traffic: 280,000 vehicles per day