The dramatic fatal crash of a big rig Monday on the San Francisco-Oakland Bay Bridge has spotlighted yet another safety concern on the troubled span.

The crash was the 44th, and worst, at an S-curve constructed just nine weeks ago east of the Yerba Buena island tunnel.

The curve is part of a new, half-mile bypass loop section installed over Labor Day weekend. The temporary bypass was added to create space above the island for a new seismically safer bridge, under construction, to eventually replace the aging east span.

The S-curve, however, is turning out to be too tight for some unsuspecting drivers.

Officials set a 40 mile per hour speed limit on the curve – 10 mph lower than the speed limit on the rest of the bridge – but some drivers aren't slowing, Caltrans' spokesman Bart Ney said.

Ney said the highway agency will add overhead reduced-speed-limit signs, rows of flashing beacons, road reflectors, and reflector strips on the guardrail, officials said.

"We are putting in everything we can think of," Ney said.

His announcement came after a big rig traveling an estimated 50 mph in the right lane failed to make the turn, flipped over the railing and plunged 200 feet to Yerba Buena Island below, killing the driver.

California Highway Patrol officials said the truck was carrying a full load of pears, and the cargo may have shifted, catapulting the truck over the guardrail.

It's the latest in a string of headline-making problems involving the east span, costing the state millions in repairs and prompting worries about bridge safety.

Two months ago, officials discovered a 2-inch crack in a beam on the cantilever section of the span. Crews fashioned a quick repair and reopened the bridge. That repair failed two weeks ago, raining broken metal onto the upper deck.

No one was seriously injured, but the failure caused a weeklong bridge closure as engineers and crews painstakingly redesigned and rebuilt the repair patch on the cracked beam.

Officials say they are inspecting the repair daily to make sure it holds, and are investigating a more permanent fix.

Meanwhile, Caltrans officials say they will move quickly this week to give drivers more warning about the S-curve.

Last week, a motorcyclist suffered a broken leg when he ran into the back of truck at the curve. A grocery truck crash there last month caused a long commute backup.

Caltrans officials defended their decision to build the S-curve.

"The design is the best possible thing we could do at that location," Ney said. "It was heavily reviewed."

The problem, he contended, is speed.

"Folks who drive 40 mph don't have a problem with it," he said.

Caltrans has posted signs on the curve suggesting drivers slow to 35 mph.

The crashes at the curve are happening on both the upper and lower decks, CHP officials said.

CHP officials said they are compiling statistics to compare crash numbers before and after construction of the S-curve, but CHP Officer Tony Tam said 44 is probably a high number for a small section of roadway.

Caltrans' spokesman Ney on Monday found himself fending off questions about bridge safety during a press briefing.

"We absolutely have not lost control of the Bay Bridge," he said. "The bridge is safe."

Caltrans officials, however, have said problems at the bridge – such as the cracked beam – show why the agency is working to replace it.

"It is absolutely an example of why we need to get the new bridge done," said Tony Anziano, Caltrans toll bridge program manager. "You can't do enough to this structure to deal with the next big item of concern, which is a major earthquake."

Replacement of the span is the last step in a seismic improvement program on state bridges. That program was launched after the 1989 Loma Prieta earthquake damaged the Bay Bridge and forced a monthlong closure.

A new east span, under construction in the bay just north of the existing span, is expected to open in 2013. The old bridge and the S-curve will then be put out of commission.

Call The Bee's Tony Bizjak, (916) 321-1059.