ST. PETERSBURG — It takes a lot for a vehicle to flip over a bridge barrier.
Speed on its own usually isn’t enough, according to the Florida Department of Transportation. Neither is a side swipe. If a car has all four wheels on the ground, the barrier should do its job and stop or redirect the vehicle.
But if a car — especially a large truck or SUV with a higher center of gravity — hits a barrier at a severe angle or after already flipping through the air, then the risk of going over is much higher, said Allan Urbonas, district design engineer for the state.
That scenario is eerily similar to what law enforcement officials say happened Wednesday morning when a collision sent an SUV into the waters off the Howard Frankland Bridge just after 7 a.m.
The SUV was traveling southbound at a high rate of speed when it started tailgating a pickup truck. The two changed lanes multiple times before the the rear left side of the pickup collided with the front right side of SUV. The pickup rotated counter-clockwise into the center concrete wall, which stopped it.
But the SUV flipped a number of times before colliding with the barrier and flipping into Tampa Bay. The body of the driver, 53-year-old Hiran Reis Vaz of Tampa, was found Thursday.
For high-riding SUVs, some of which are more prone to overturning on impact, the chance of sailing over the barriers is greater than the standard car, Urbonas said.
And while the barrier of the Howard Frankland’s southbound span was built to the appropriate standards in 1990, the state’s standard has since risen to 38 inches — six inches higher than the barrier the SUV flipped over Wednesday.
Whether or not those six inches would have made a difference in that crash is hard to tell, said Kris Carson, a department of transportation spokeswoman. There are too many factors at play, such as speed, angle of impact and the flipping of the vehicle, for officials to address that question.
The state’s design standards for traffic railings mimic those of the American Association of State Highways and Transportation Officials. Both agencies have raised their height requirements over the years as vehicles have gotten larger and heavier. But a roadway’s railings need only comply with the standards in place when the barriers are constructed, Carson said.
“There are cases where we do go higher,” Urbonas said. “It’s a give and take. If the barrier is higher, it’s also stiffer ... and when you do hit, it’s more of an impact to the occupant. Those every day hits become a little harder on the vehicles.”
The point of the railing is to try and redirect the majority of the traffic that hits it, Urbonas said. Hardly a day goes by that a vehicle doesn’t bump, scrape or smack into the concrete barriers on the Howard Frankland Bridge.
“You will notice a lot of scarring and tire marks on the bridge. Those railings do get hit quite a bit,” Urbonas said. “They, for the most part, do a good job on redirecting errant vehicles.”
But state transportation officials plan to raise the existing 32-inch barrier to 42-inches when they start construction on the new Howard Frankland bridge in 2020. That’s because the new roadway will also have a path for bikes and pedestrians, which usually leads officials to go above the standard height requirements for traffic railings.
Engineers are also likely to raise the height of a barrier when the road sees heavy truck traffic or if there’s a need to protect critical structures, like bridge piers, Urbonas said.
Times Senior Researcher Caryn Baird contributed to this report.