Northwestern Pacific Railroad Network

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Here is an interesting website (with videos) of a reduced clearance railroad over-crossing.  Approximately once a month a tall vehicle, usually a rental truck, crashes or scrapes the "crash beam" despite signs and warning lights which activate when such a vehicle is detected up to three blocks away.  The bridge doesn't get damaged because of the crash beam, which appears to be amazingly solid.  The videos clearly show some major forces hitting it and it doesn't yield!  However, the trucks suffer dearly.

The bridge is located at:  201 Gregson St in Durham, NC

Website:

http://11foot8.com/

Hope you find this interesting!

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In this image we are about a block away from the railroad overpass ahead in the distance.  This road is one-way under the railroad, so crashes happen on the near side only.  The red arrow in this photo indicates the through-beam sensors used to detect excess height vehicles and start the yellow flashing lights adjacent to the sign "OVERHEIGHT WHEN FLASHING".

I guess they were also having problems with drivers mowing down pedestrians, hence the painted "island" ahead of the crosswalk to prevent lane changers when one lane stops to allow people to cross.  (see photo, above)

Can't use red lights because that means "stop".  Cars ahead of the offending truck need to proceed to prevent gridlock.

I was thinking if they had a long bank of yellow lights over the that crash beam it should get driver's attention.  But then I recalled that if they go to such lengths in one intersection then they have to do it everywhere else two yellow flashing lights are used or invite litigation from opportunist lawyers when accidents happen.

The plan is to put in a traffic signal that will in fact stop traffic, but only briefly.  The idea is that by the time it goes green again the truck drivers will have had their Epiphany.  I really doubt it will help much.  See the attached WSJ article.

Attachments:

This Marin I.J. article, dated 2014-08-19, states that the Sir Francis Drake clearance under the Dirty Harry Trestle was 17.5 feet:

Part of Clint Eastwood's "Dirty Harry" Larkspur train trestle remov...

Despite what the article says, I know that the Sir Francis Drake NWP over-crossing (a.k.a. Dirty Harry Trestle) was hit more than one time.  The incident that I remember most was caused by a dump truck working adjacent to the trestle.  The driver had the bed fully tilted as he just dropped a load to fill a hole just east of the trestle.  He continued to pull forward right into the trestle with enough force that the (front?) two wheels came off the ground.  I think the fire department had to remove the driver on a litter attached to ropes.  There was an I.J. story about this, but probably in the early 1980's.

On my return commute each day in 1984 I would go under that trestle and the visible damage was an ongoing reminder of what happened there years earlier.

OK, that Super Dave gag was hilarious too!  .... and quite relevant!

Back when, before Westinghouse's air brake got the brakemen off the roofs of boxcars, there were "tell-tales" to warn of low overhead clearance, such as a tunnel.  These were horizontal bars with ropes hanging down which would swat anybody on the roof of a car and let them know to get down off the roof and avoid being mashed against the tunnel lintel or whatever.  Here, chains instead of rope would certainly warn vehicles not to try to pass under the ROW a lot more effectively than flashing lights (and without the electrical complexities of the system described.)

So that's where the phrase "tell tails" came from!  In one of my NWP books there is a picture of this arrangement in front of the south portal of the Alto Tunnel.  Of course, there are plenty of photos of "tell tails" on other railroads.

The question, among others, is whether a chain (or chains) hitting the box of a box truck or van could be heard inside the cab of said truck, and if so, would there be enough time to slow down and stop?  This road has a speed limit of 25 MPH.  It's not like entering a parking garage.

This is a deceptively complex problem which many clever people have attempted to solve over many years of trying.  The only definitive solutions are very expensive.  Due to the cross street ahead onto which tall vehicles are normally supposed turn, the risk of damaging or scratching these vehicles is not acceptable unless they do, in fact, attempt to go straight under the bridge.

It is these complexities that make this an interesting story.

My son, who is a licensed civil engineer and working on the California High Speed Rail project, had this to say:

For Caltrans the standard roadway clearance is 16.5' from finished grade of the roadway to the bottom of the structure soffit.

[In architecture, soffit describes the underside of any construction element.]

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