The Drive: Are highway bridge rails too low?

  • Article by: TIM HARLOW , Star Tribune
  • Updated: January 20, 2014 - 8:11 AM

In the darkness of the frigid morning rush hour on Jan. 7, Anne Spiess took the ride of her life when her pickup truck flipped over a bridge railing and plummeted 40 to 60 feet onto a frozen holding pond below.

The 54-year-old Maplewood woman was driving on the flyover bridge that carries traffic from northbound Interstate 35E to westbound I-694 in Little Canada when she lost control of her 2001 Ford Ranger in icy conditions that developed as temperatures dropped well below zero.

Traffic cameras recorded the freak incident and the Minnesota Department of Transportation posted a video showing the pickup twisting in midair and narrowly missing motorists driving below on eastbound I-694.

“It was very frightening. It was surprising to see a vehicle go over like that,” said Nancy Daubenberger, MnDOT’s state bridge engineer. “It’s terrible to see that ­happen to a driver on one of our roads. We want to prevent that in any way we can.”

Thankfully Spiess survived, but the incident has MnDOT revisit­ing discussions the agency has had in the past about bridge rails and whether new designs for high-speed roads with curves are needed to keep vehicles from going airborne, Daubenberger said.

Bridge rails are a safety feature designed to contain and safely re­direct errant vehicles back into traffic. The rail on the I-35E flyover bridge is a standard concrete wall that stands 32 inches and meets crash test criteria set by the Federal Highway Administration. Those standards, required for all bridges on the national highway system, include the ability to contain and redirect a vehicle, the danger the barrier presents to occupants when vehicles hit it, the after-collision trajectory, and the possibility of involving other motorists.

“Although our standard rails have been crash-tested, they are generally developed for crash situations that encompass a large majority, but not all possible collisions,” Daubenberger said. “With all the testing done, the incident [on the flyover] is outside what normally would be the result of what would happen when crashing into the rail.”

A few years ago, Daubenberger said MnDOT had discussions about proposing higher rails. But the department passed on the idea after evidence showed that rails higher than 32 inches increase risks to vehicle occupants. (The new I-35W bridge over the Mississippi River near downtown Minneapolis has a 34-inch rail, but the extra 2 inches will allow for pavement overlays.)

“When a driver crashes into a higher concrete or metal barrier, the risk of a driver’s head crashing through the window and hitting the barrier was high. A 32-inch rail shows drivers could be redirected to the roadway with less risk to injury,” Daubenberger said.

As new bridges are built, Daubenberger said MnDOT will evaluate crash-tested rails. The agency also could develop its own rail, but it still would have to meet federal crash-safety standards.

When it comes to safety, motorists hold the key. Minnesota law enforcement officials cited snowy or icy road conditions in more than 45,000 crashes that resulted in 117 deaths and 13,721 injuries from 2010 to 2012.

The advice: “MnDOT encourages drivers to use caution, especially on ramps and bridges when conditions cause them to be icy.”

Follow news about traffic and commuting at The Drive on startribune.com. Got traffic or transportation questions, or story ideas? E-mail drive@startribune.com, tweet @stribdrive or call Tim Harlow at 612-673-7768.

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