ORINDA -- One drunken driver striking a tunnel curb started the chain of events that led to one of the deadliest traffic tunnel fires in U.S. history.

Seven motorists died inside the Caldecott Tunnel on April 7, 1982. They were trapped inside by a string of unsuspecting motorists who followed their vehicles into the third bore.

Janice Ferris, 34, a San Leandro bookkeeper, was driving her compact Honda after a night of socializing in Walnut Creek when it struck a curb in the Caldecott Tunnel third bore and came to rest in the fast lane. According to Times' stories, she had a blood-alcohol level of 0.17.

Within minutes, the front wheel of a gasoline tanker struck Ferris' vehicle.

Then a speeding AC Transit bus -- out of service at the time -- swerved to avoid the two vehicles but ended up hitting both of them.

The bus crash caused the tanker to turn over and spill 8,800 gallons of fuel, which soon ignited an inferno.

Unfortunately, other drivers -- not warned of the danger ahead -- had entered the tunnel shortly before the explosion.

Some fled the tunnel in time, but seven people died, including Ferris, the bus driver and the tanker driver.

Investigators with the National Safety Transportation Board blamed the accident on Ferris' erratic driving; the gasoline tank driver for inattention for striking the car; and the bus driver for passing the truck too fast.

The safety board concluded, "Also contributing to the severity of the accident and injuries were the lack of adequate monitoring capabilities and variable message signs or traffic signals at the entrance of the tunnel and within the tunnel, and the lack of a communication system between the tunnel personnel and tunnel occupants, which if present, might have facilitated occupant evacuation."

Another contributing factor, the board concluded, was the presence of a tanker trunk with flammable fuel.

In response, the state passed a law banning trucks with flammable liquids or poisonous loads in the Caldecott Tunnel, except from 3 to 5 a.m.

Standards for designing and operating traffic tunnels also were changed, resulting in safety measures built into the Caldecott fourth bore, which will open Nov. 16 or 17.

Contact Denis Cuff at 925-943-8267. Follow him at Twitter.com/deniscuff.