Sunday, December 2, 2012

Eleven Foot Eight

Our headline photo sets the stage for todays topic. Looking carefully near the center of the photo, you see some sort of machinery impacted almost dead center with a cryptic yellow highway sign with the inscription: "5.1 m" - 5.1 meters or 16 feet 9 inches. Here is another view of that machinery, a John Deere 240D  excavator.

The innocent bridge knocked almost completely off its pier, was a Canadian Pacific Railroad crossing over Trans Canada Highway 16, near Lloydminister, Saskatchewan. Fortunately, this track serves industrial areas.

The 47 year old driver plead not guilty to the charge of "exceeding the maximum dimensions specified in a permit under the Highway Transportation Act."

Speed limit on this stretch of Highway 16  is 80km, or 49.7 mph. He was NOT wearing seat belt, and complained of sore and swollen wrists!  I would suggest that going instantly from 50 mph to zero, unconstrained, he was lucky sore wrists is all he suffered!

The bridge was stabilized by cranes the following day. The afternoon of October 12th, two heavy cranes were used to lift the span, which was taken to Edmonton where it was declared salvageable. Following repairs, it was placed back in service at its original location! See further reading below.

Comparing and contrasting a bridge knocked off its piers to a bridge under constant assault, for which an unusual solution has been applied to protect it.

One of my Blog readers recently sent me a link to a YouTube video of trucks and recreational vehicles routinely decapitated by a railroad bridge. The Norfolk Southern bridge, is around 100 years old! And like it, there are hundreds of "legacy" rail bridges over highways, streets and roads, built during an era of smaller motor vehicles.

Todays Federal standard for bridges over highways, calls for clearances ranging between 16' (4.9 meters) to 14', depending on the type of road being crossed. And 17' for pedestrian overpasses and signboards. See Federal Highway Administration ruling on bridge clearances.

In Durham North Carolina, a one way street, South Gregson, feeds traffic into a business park, passing under the Norfolk Southern tracks.

Northbound traffic feeding away from the business park, do so over a grade level crossing.

The Norfolk Southern railroad bridge spanning South Gregson Street in Durham, North Carolina, is what I call "a legacy" overpass. Vehicles exceeding 11'8" (3.55 meters) will be "decapitated." And it has been struck countless times by drivers who are either inattentive or ignorant of their vehicles height.

In fact it happens so often, that a fellow by the name of Jürgen Henn, set up a video camera in his second floor office vantage point overlooking the South Gregson Street underpass. His videos have racked up thousands of viewers. Indeed, as you watch the video, notice the pickup towing a large travel trailer. Only the GPS tower and roof mounted air conditioner are clipped off ... at precisely 11'8"!

Mr. Henn has established a website, featuring memorable moments and very close calls. He's even marketing a tee shirt to monument man vs bridge!

The initial collision can result in collateral rear end collisions as a result of the "immediate" stop, resulting in debris on the highway, resulting in additional traffic tie-up.

So loading up Google Earth program, I proceeded to Durham, North Carolina, to take a closer look at the South Gregson Street Can Opener!  This is what I discovered using the "Street Level" tool:

Norfolk Southern Railroad owns the rail trestle. Since their number one concern is the safe passage of trains, they installed a steel I-beam "crash structure at precisely 11'8" just in front of the bridge.

A series of sensors monitors the 25 mph (40 km) traffic. If an approaching motor vehicle exceeds 11'8" (3.556 meters) height, flashing yellow lights are activated,

allowing the vehicle driver ample time to turn left or right before impending doom! Eleven foot eight isn't very high.  My GMC Vandura is six foot eight. Mr. Henn has included a shot of a beam with a severe indentation!

And apparently, all drivers seem to obey the "one-way" signs. Since South Gregson is a one way street, no similar protection required on the "downstream" side of the structure ... so far!

Despite the warning signs, lights and barrier, "the hits just keep on coming…"

See Also:  "Bridge Protection with Pizazz ..."

Further Reading:
•  How the CP bridge span was repaired
•  Railroad Merger Trees (located in right margin of this Blog)

2 Comments - Click here:

Anonymous said...

Long time reader, right since the days of your posts on railpics before you done Oil-Electric. I used to drive for NZRailways and there was one overpass that gave me the creeps on account of the number of "stoopid" truckies down here. On the rail if you enter these co-ords -40.072998,175.416936 in you will see how the railwayline flies over the highway at near grade level, State Hwy 1 is trenched to allow movement and the propensity for the truckers to be "tired" around this part of the country always worried me that I'd not see the damage until it was to late. Considering the high number of hits and wedges it never happened though but I still worried none the less. Note the strengthened strike barriers.

Great article as always.

Unknown said...

The Lloydminister bridge accident occurred only weeks after audio recordings of oversize load permit requests began. Review of the recording proved the trucker gave a wrong load height. The bridge should have been protected by a crash beam in any case

Post a Comment

"Comment" is for sharing information related to this article. "Anonymous" comments are not published.