An underground light rail tunnel in Texas.
https://3.bp.blogspot.com/-N37TE1Guh...Uptown1-07.JPG

https://www.cookfamilyhome.com/fulph...7/pa040023.jpg

http://www.jtbell.net/transit/images.../Cityplace.jpg

Me 3. I didn't want to be a naysayer before the election, but I am still a little skeptical about having two river crossings within the budget. Once the engineering details get worked out, I think the crossings will be the most obvious hit in Value Engineering. For instance, I have some trouble imagining bridge crossings if the goal is to enter a tunnel before 4th Street.

Bridges would have to be high enough to be out of the flood plain and allow the hike and bike trail to pass underneath. The trail near Trinity is at a higher elevation to go around the boat house and Waller Creek Tunnel. The tracks would have to cross Cesar Chavez at the surface and descend into a tunnel before 4th Street. Light rail trains cannot exceed about 6% grade, so the tunnel portal has to be more than 1 block long just to get into a shallow cut and cover tunnel. Cap Metro has been selling the idea that the downtown underground stations will be in deep tunnels, with an extensive amenity rich mezzanine level. I think that means that at least 2nd and 3rd would have to be cut off by the tunnel portals. I think that will be unacceptable to the City of Austin and the public. Cutting Cesar Chavez off with a tunnel portal would be a fatal flaw, in my opinion.

For these reasons, I am predicting deep tunnels under Lady Bird Lake, which also means that the tunnels will need to extend a significant distance north and south before they can come up to grade because they will be fighting against the surface topography which rises fairly steeply either side of the river.

I remember back in 2000, when some of us were advocating for tunnels, the consultant from Parsons Brinkerhoff did a quick estimate that tunnel portals would need to be between 1 and 2 miles long.

For this reason, I think we might end up with a single river crossing shared by both the Blue and Orange lines in the first phase, with provisions to add a second crossing in the future when there is higher ridership and the gold line is upgraded to light rail.

There is also the issue of turning 90 degrees in the tunnels. Light rail vehicles can barely make a 90 degree turn within our 80 foot ROW widths. They have to be travelling at the lowest speed possible, and will create a lot of vibration and noise. Fortunately, you want the trains to be traveling slowly close to a station. However, stations cannot be located on a curve and have to be about half a train length down a straight tangent from any curve. That means there will be an interest in clipping the corners of properties. This would be a bigger issue at the surface, but even in a tunnel, they will need to thread between the foundations of existing and future buildings at corners.

Knowing all of this, it makes me chuckle when I see people question why it takes so long in the design and engineering phases before construction can even start. I think the next couple years are going to be fascinating for transportation geeks between Project Connect and the rebuilding of I-35.

That Green Line in Boston is ancient and it shows. I think most of the trains on that line don't even have level boarding so it takes everyone a few extra seconds to get on. They also feel pretty cramped to begin with.

Special events like a baseball game will always have this problem to some extent. The Red Line will definitely have this issue when McKalla station is operational. Auditorium Shores could also have this issue during special events. Luckily the Orange and Blue lines should run so frequently that anything at UT or downtown should be a breeze. And like Freerover said, the tunnel will go a long way toward keeping things moving efficiently.

Yea, it would be nice if the red line had stations long enough to support double trains for big events.

Looks like Vegas is going all in with TBC. Should serve as a good test run to see if this stuff really works. I'm skeptical so time will tell.

https://www.teslarati.com/elon-musk-...pproval-video/

It'll work fine on the strip as a fast taxi service for people on vacation who aren't budgeting their money.

Leaving fenway I'd a special level of hell on the T.

NYC leaving a yankees or Mets game is amazing. Knicks/rangers barely count given the games are at Penn station. Nets are a bit rougher but not bad.

Chicago is ok after a Doc or cubs game

Per Wiki https://en.wikipedia.org/wiki/Green_Line_(MBTA)

"With an average daily weekday ridership of 152,200 in 2019, it is the second most heavily used light rail system in the country. The line was assigned the green color in 1967 during a systemwide rebranding because several branches pass through sections of the Emerald Necklace of Boston.
The four branches are the remnants of a large streetcar system, which began in 1856 with the Cambridge Horse Railroad and was consolidated into the Boston Elevated Railway several decades later. The branches all travel downtown through the Tremont Street subway, the oldest subway tunnel in North America. The Tremont Street subway opened its first section on September 1, 1897, to take streetcars off overcrowded downtown streets; it was extended five times over the next five decades."

Yes, the oldest subway tunnel in the USA was initially built for horse powered trolleys converting to electric powered trolleys.

I'm guessing the turn around loop at Lechmere Station was a lot more pleasant back in the horse trolley days. I stayed near there on vacation once and man that train screeching was LOUD. I understand they're extending the green line so there's no loop there anymore.

If I were king, I would extend the Austin Red Line all the way to Lamar and have the tracks make a tight vertical corkscrew around the Gables Towers to form our historic rail screeching district.

I think you're seriously discounting the topography difference of downtown from the lake. I'd expect (and what seems to be the proposal) is a bridge crossing of the lake, and then entering the tunnel south of Cesar Chavez.

The nominal elevation of Town Lake is 428 ft. The elevation of CC/Trinity seems to be ~488 ft.

https://en-us.topographic-map.com/maps/ndx/Austin/

It's a little hard to find a specific flood elevation for town lake. The document linked here
https://stateimpact.npr.org/texas/20...dam-in-austin/

Seems to suggest a rise to 439 feet at Longhorn dam during a 100 year event.

That's quite a bit of elevation to work with.

Honestly, if improving or replacing Longhorn dam is needed to avoid a tunnel crossing of the lake, I'd expect that to be on the table for Prop A funds (and an appropriate use).

At your 6% grade, then the 1000 feet from CC to 4th is enough to be 60 ft deeper, enough for a mezzanine level (under the park?) above the tracks.

I think there were some open houses with cap metro that showed the orange line being underground till south congress which would include an underground auditorium shores station.

Yea but that got shaved back. You can't easily add tunneled sections to the budget.

oh well... :(

I think the trail on both sides is easy. You just need an arch gap in the bridge supports for people to pass under. It doesn't need to have 20' clearance. I feel like blue line goes underground at the MACC parking lot, goes down red river, uses the corner of the convention center to round that corner to 4th with an underground station at the fire station parking lot. The future gold line would keep going north on Red River instead of Trinity. I assume you would need each tunnel at different elevations for turning clearance and so you can have the future gold line split without crossing into opposing train tracks.

This podcast says everything I feel about Musk's tunnels as "mass transit"

https://www.youtube.com/watch?v=sWva...X8VLDoiFglZdV4

It was only a couple yrs ago that this felt like a joke. Now it's reality. :)
https://www.austinchronicle.com/news...-soccer-train/

I want my floating soccer stadium and I want it NOW

From the article:

Because the U.S. doesn't have its own form of crazies when it comes to sports....

Man, as much as I like the current stadium and its obviously convenient location along the Red Line, proximity to the Domain, etc., Butler Shores would have been spectacular.

You might have missed the date of the article.

Definitely. Butler Shores 4Ever