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Bright line information

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Posted by Overmod on Saturday, August 8, 2020 4:49 AM

BaltACD
Human vision has a latency in the frame rate that the brain can handle.

This is almost completely different from the 'backward wheel' artifact.  You'd far better ask yourself the more basic question 'why does seeing backward-turning wheels at speed annoy me?'

As I recall from psychophysics, image-formation latency in people is about 19ms.  Substantial image change faster than that results in a blur, or due to human 'image processing' the disappearance of the thing changing faster -- hence the reason you can see the brake detail behind fast-turning car wheel spokes.  

Film on the other hand is shot not only at a fixed frame rate but with a shutter speed fast enough to eliminate more unpleasant motion blur as well as give varied depth of field and a couple of other effects.  Movies are a trick, a way of fooling the human perceptive system into thinking it is seeing smooth motion, but the actual information coded into the individual frames is massively reduced, and one very significant consequence is that phase information is lost.  The actual thing captured on the film at 'wheels backward' speed is like stroboscopic vision with the pulse rate slightly slower than the advance between identical spokes -- this being indistinguishable from the same wheel turned slightly backward at much lower speed at the same lighting repetition rate.

Far more 'fun' and annoying are some of the visual effects from CCD cameras, which can have really fast effective 'shutter speed' but long image-processing time and hence low effective frame rate separate from nominal resolution.  Propellers shot with these have all sorts of weird distortions in addition to what can be wildly varying perception of rotational direction.

Meanwhile there is a perceptual 'quirk' that recognition of a processed image in the brain can 'freeze' certain images; the original determination of that 19ms. acquisition was done stroboscopically to see how long an item needed to be illuminated for a subject to 'remember' details of it... the conscious memory taking much longer to form.  When I first joined SMPTE I had the bright idea that a vastly enhanced perception of dizzying speed might be produced by combining the two effects of blur and periodic capture, by shooting most frames with corresponding average blur but interposing periodic frames with high stop-motion resolution, a bit like the research into recognizable subliminals.  This worked remarkably well... at recreating precisely the confusion in image recognition that makes people disoriented and sick watching roller coasters and the like without vestibular coupling.  It certainly worked to enhance the thrill of speed ... the thrill of helpless speed where you have no idea where you'll be pulled next.

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Posted by CMStPnP on Monday, August 10, 2020 10:00 AM

Wow! Brightline ends agreement with Virgin Trains.    That was kind of sudden.   I guess they got sick of waiting for the capital pay in from Virigin.

https://trn.trains.com/news/news-wire/2020/08/08-digest-brightline-ends-marketing-agreement-with-virgin-group

 

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Posted by rdamon on Monday, November 30, 2020 11:54 AM

Spent the holiday with some windshield time in Central Florida.  Drove from Orlando to Cocoa along FL-528. Grading and bridge construction was in process along the whole route. 

There is a large stockpile of concrete ties at the intersection of 528 and Industry Road.

It is visible in the Google satellite view.

 

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Posted by blue streak 1 on Wednesday, March 3, 2021 10:10 PM
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Posted by blue streak 1 on Wednesday, March 10, 2021 10:27 PM

Brightline is going to build a tunnel under state route 528 by using a box jacking method.  They expect it will only take 10 days.  Does anyone know exactly how the method works ?  In a way it sounds line the way casings are jacked under RRs and roads but on a very big steriod ?.  The number of workers seem to indicate that workers will be working at the face ? 

Brightline set to make history with box-jacking method - Railway Track and Structures (rtands.com)

EDIT: Here is a link

Jacked Structures - Box Jacking

 

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Posted by BaltACD on Wednesday, March 10, 2021 10:49 PM

blue streak 1
Brightline is going to build a tunnel under state route 528 by using a box jacking method.  They expect it will only take 10 days.  Does anyone know exactly how the method works ?  In a way it sounds line the way casings are jacked under RRs and roads but on a very big steriod ?.  The number of workers seem to indicate that workers will be working at the face ? 

Brightline set to make history with box-jacking method - Railway Track and Structures (rtands.com)

EDIT: Here is a link

Jacked Structures - Box Jacking

Considering the typical Central Florida elevations (or lack thereof) - who is going over and who is going under.

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Posted by blue streak 1 on Wednesday, March 10, 2021 11:01 PM

Bright line is going under 528

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Posted by rdamon on Thursday, March 11, 2021 5:34 AM
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Posted by BaltACD on Thursday, March 11, 2021 6:57 AM

blue streak 1
Bright line is going under 528

Which then begs the question - how much of a dip in the line of the right of way will their be and over how long of a distance?  Will the clearance plate only clear Brightline or will it be built to current Class 1 unrestricted clearance plates?

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Posted by CSSHEGEWISCH on Thursday, March 11, 2021 9:55 AM

The clearance diagram may not be the biggest issue.  Considering that most of Florida is about 10 feet or less above sea level, drainage may be a bigger problem.

The daily commute is part of everyday life but I get two rides a day out of it. Paul
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Posted by Overmod on Thursday, March 11, 2021 10:37 AM

BaltACD
Which then begs the question - how much of a dip in the line of the right of way will their be and over how long of a distance?

Box jacking is inherently horizontal, although it could be started in a 'hole' or angled to a gradient.   That they are using box jacking in the first place and expect to be finished in 10 days implies that 528 at this point is on a berm of adequate height.  Obviously if the new line were to go 'over' there would be no need to 'tunnel'; they'd just build up embankments over time and just bridge the road at the end.  Looking at the aerial view you can see what a pain the necessary construction for a high-speed 'flyover' would entail...

Will the clearance plate only clear Brightline or will it be built to current Class 1 unrestricted clearance plates?

I can't imagine why freight would be operated on a HSR extension of this kind; if it were, the logical thing would be to regrade the approaches on 528 and install an actual overbridge at the crossing, not a particularly difficult piece of civil engineering even for MC's 'Highway bubbas'.  That they are essentially directional-drilling on a large rectangular scale implies to me that minimal clearance gage is in play...

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Posted by MidlandMike on Thursday, March 11, 2021 7:42 PM

Overmod
That they are essentially directional-drilling on a large rectangular scale implies to me that minimal clearance gage is in play...

The linked article says "The underpass, once constructed, will measure 31 ft high by 43 ft wide, will be the length of a football field and will accommodate two trains side by side."

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Posted by BaltACD on Thursday, March 11, 2021 10:00 PM

MidlandMike
 
Overmod
That they are essentially directional-drilling on a large rectangular scale implies to me that minimal clearance gage is in play... 

The linked article says "The underpass, once constructed, will measure 31 ft high by 43 ft wide, will be the length of a football field and will accommodate two trains side by side."

At 31 feet high it is being constructed to the current clearance plate which, I believe, requires 25 feet from top of rail to the bottom of whatever is over top of the rail.

I am wondering how far below Route 528 the jacked in structure will be?  I am GUESSING 10 or more feet below Route 528 so the bottom of the jacked in structure will be 41 feet or more below the grade of Route 528.  Wonder how far out the grade to the bottom of the structure will be extended from the structure?  With a 1% grade we are talking about 4100 feet in each direction.

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Posted by Overmod on Thursday, March 11, 2021 10:29 PM

If I remember correctly we discussed the Goldenrod Road crossing a while back -- but I don't remember box-jacking being mentioned or discussed.  Same for the LIRR improvement project, where I remember seeing only bridge-raising projects.

I'd be interested to see the drainage plans for the completed structure.

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Posted by MidlandMike on Friday, March 12, 2021 9:35 PM

The linked article says the box-jacked tunnel will be built under Route 528 just west if US 1.  Looking at Google Earth, this is where the expressway is already on a fill leading to a bridge that crosses over the FEC mainline and US 1.

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