Funding Friday: The L-Ternative Bridge

Every day 300,000 people take the L train to and from work. I am not sure if that is 300,000 people or 150,000 people going in and out, but either way, it’s a lot of people.

And the MTA is going to shut down the L train for 15 months, starting in April 2019.

So this is a big deal for NYC, and a big deal for NYC tech companies. In an informal and unscientific poll I took this week of NYC tech company CEOs, about 20-25% of the employees of NYC tech companies in Manhattan take the L train to work.

So how are these people going to commute for those 15 months (which is almost certainly going to take longer than 15 months)?

The best answer I have heard from the NYC government is “more buses going over the Williamsburg bridge.” Which is an option but not a fantastic option. The Williamsburg bridge is already a crowded transportation mode during the morning and evening rush hours and more buses means something is going to have to give.

So this week, I saw this cool project pop up on Kickstarter.

Take just one minute and watch this video:

Pretty cool, right?

My dad was an Army Corp of Engineers officer his entire career and retired a Brigadier General. He knows a lot about pontoon bridges. So I asked him if this idea is viable. He said:

Having built several pontoon bridges, including some designed for 60-ton tanks, I know the idea is feasible.
(One of my bridges was across the Rhine River.  That was done for the first time by Julius Caesar.)
Drawbacks:  they are expensive, have low speed limits, and require constant maintenance.
Still, if the permanent solution in that location can’t handle traffic for some time, this could be a temporary replacement.
Interesting idea. Thanks for sharing it with me.
Love, Dad
That’s all I need to know that this will work. My dad knows his stuff when it comes to pontoon bridges.
So if you want to see this idea get some traction, go to Kickstarter and support this project like I did this week.
#hacking government#NYC

Comments (Archived):

  1. karen_e

    Backed! Civil engineers deeply embedded in the VC community: Fred’s dad, JLM, Deb Kemper of Golden Seeds. Who else?

  2. awaldstein

    Know zilch about pontoon anything but i trust your dad on this one.Know a bit about a city leadership that is not only not thinking outside the box but has its head in the sand–which obviously is the opposite of its mandate to protect you and I and all of us city dwellers.Buses–i hate the idea of gas fueled anything increasing.But if we are going to go the route of above ground transportation maybe a leap further into the future with electric and semi-autonomous traffic lanes is something to bolt on finding some part of a better future in an immediate real problem?

  3. kidmercury

    the L goes fairly deep in to bklyn. isnt there still an issue of getting from one’s home to the pontoon bridge?

    1. awaldstein

      the bridge plan by definition appears to hinge on buses as the answer. Only handles the east river issue.

      1. kidmercury

        in that case, hope nyc startups are investing in their remote work setups…..

        1. awaldstein

          the whole idea of being in NY is of course proximity and community as a work environment.the opposite of remote.i only hope that innovation will end up making something new from this not just ways to plug the holes in the dike.

    2. Michael Elling

      Electric folding bikes are phenomenal. Easy to go 10 miles without breaking a sweat at 15-18mph. Can be carried and stored anywhere. Of course rainy days are a bit of an issue, so buy a rainproof 1 piece or work from home. The avg commute time will be cut by half.

  4. curtissumpter

    Fred, this is a related question.Would you ever consider sitting on the MTA Board. I was looking at this article in the WSJ where they’re planning to spend 200MM on renovations of subway stations. (200 MM!!).…That wouldn’t bother me if this NYT article didn’t come out.…Then I looked at the Board.… I don’t many non-government contract based business person at all. I see bureaucrats and former union officials, not to mention it’s awful homogeneous. Would you ever consider sitting on such a board and getting other business people to sit? It seems to be the source of the problem and you have experience sitting on boards.

    1. fredwilson

      it is a theoretical question as i have never been asked and don’t expect to be. but yes, i would consider it if asked

  5. JimHirshfield

    Thanks for floating the idea by us.

    1. kenberger

      Jim, you always barge in.

      1. JimHirshfield

        Nah, span a long time.

        1. Matt A. Myers

          Water you mean?

          1. JimHirshfield

            I dunno. I’m just going with the flow.

    2. Girish Mehta

      Nice !

    3. fredwilson

      you never miss an opportunity to find the humorous angle. that is outstanding.

      1. JimHirshfield

        Ah, geez. Thanks for sinking of me.In all seriousness, love the email from your dad. More dad in blog posts please.

  6. Vanderlyn

    Interesting idea that is of a piece with many other intriguing ideas (e.g. gondolas), but doesn’t really move the needle re: transporting commuters.Contra your blog post, the MTA estimates that 80% of Brooklyn-based L train riders will take other subway lines into the city during the shutdown – particularly the M train and the G train.The average L train (8 cars) can fit around 2,000 people at max capacity. Running 2 minute headways (30 trains/hour), that’s 60,000 riders per hour. A standard NYC bus holds around 65 people at max capacity. You would need nearly 1,000 buses per hour to match hourly subway capacity.Not sure why this basic analysis is not part of the Kickstarter.

  7. Josh Jackson

    Can we think of the larger impact of this Kickstarter? The risks and challenges involved with this project is the larger issue and urgently important.

  8. jason wright

    I was going to ask what ‘L’ stands for, but of course L (L1) always stands for ‘Love’, and this world needs more of that.My sign of the times reaction to the pontoon idea is that it could be an inviting target for a determined adversary. A temporary structure like that would be more vulnerable than a permanent bridge, and security checks would severely slow down traffic flow.p.s. L (L2) = Elevated?

  9. Tom Labus

    A fleet of auto rickshaws and dorms in Manhattan, like those Tokyo sleeping pods. What a mess.Your dad’s an historian too. Caesar’s army in Gaul could move 50 miles in a day on foot, build a bridge and visit you in the morning before you woke up

    1. fredwilson

      and he speaks something like eight languages

    2. JLM

      .Amongst professional soldiers, ground pounders, the marching distance of Caesar and Stonewall Jackson is always debated as to how far, how fast.Jackson used to hang stragglers in the Shenandoah Valley in the Civil War. Hanging stragglers will put a hop in your step. He moved combat units long distances day and night. That was also tough terrain going east to west but easy terrain going north to south.The big issue is the terrain. A soldier can march down a level, dry road for a long, long time and cover a lot of miles. Any time you get above 20 miles, you are not going to get much from those troops until they rest.Even though you may have fit, young 20-something men and junior officers, the senior NCOs and officers can’t exert that much energy and recover quickly.In peacetime and in training, I’ve moved company sized units (200 men or less) 25 miles overnight on foot, but it is tough and you will have lots of blisters and injuries like chafing.I became a soldier after reading Caesar’s Gallic and Punic Wars in Latin.I should have become a Latin scholar? Nah!JLMwww.themusingsofthebigredca…

  10. JLM

    .Built plenty of floating bridges in my days in the combat engineers. Taught M4T6 floating bridging to the West Point cadets in the summers. Held the record for the fastest crossing of the Imjin River in South Korea and the Rhine River for the M4T6. That is no longer the cutting edge equipment.This bridge could be built but the challenges are enormous -1. The regulatory hurdle with the Coast Guard is likely not going to be cleared. They have no dog in the fight other than obstacles to free navigation.2. The East River is tidal with a 5′ normal difference. This is a big problem, but not insurmountable. The abutments will have to be adjustable to allow for the up-and-down movement of the bridge with the tides.3. The Bailey Bridge is typically used for a fixed, static application though it is also used for pontoon bridges. There is not a “standard” pontoon which is mated to the BB as there is for the M4T6.4. The big problem is the drawbridge. I don’t see that working for a number of reasons.When you open that drawbridge, you take the continuous chord of the bridge and cut it in the middle – the weakest point. The bridge will flex and make it hard as Hell to mate those open bridge sections. I have never seen this done.You are trying to balance the current, the tide, the wind, and the loads while creating an enormous dynamic load. Water moves the second a force is applied to it.When that continuous supporting chord of the bridge is opened and the drawbridge weight is transferred, everything will start moving. Everything. The wind load will not be negligible.The pontoons at the drawbridge have to be sized to carry their normal load, the additional load of the drawbridge sections, the dynamic load of movement, the twisting load of the wind, and a huge factor of safety.The pontoons will likely have to be continuous for a couple of hundred of feet to make this possible.The machine lifting capacity to lift those sections is enormous.I don’t see this working.5. There is, however, a simpler solution, a swinging bridge section which swings out of the way to the downstream side. A large section is uncoupled, released, and swung creating a similar opening. Bridge pusher boats – a standard thing in the military — like a tug move the swinging bridge section out of and back into place.6. Three thousand feet is a damn long bridge and multiplies the cumulative impact of any small fault. Bailey Bridges are, essentially, steel Legos which are connected by driven pins. They are not delicate, but they have to fit to work. At three thousand feet, the cumulative errors become troubling.7. The BB sections will have to be wider and taller for the required strength. The pontoons will have to be 5X what they calculate to require and they will have to have emergency pumping features. One of those babies goes down and the whole thing is screwed. That is why you have to have the high factor of safety.8. I doubt there is any type of “standard” barge which would work for the combination of buoyant load and dimensions.9. It probably makes sense to have the travel lanes side by side and eliminate some of the interior BB sections.10. The dynamic load has to be carefully controlled to prevent the development of resonant frequencies in which a dynamic wave is reflected and multiplied because of resonance.11. The travel speed cannot be more than 25-30 MPH because the brittle BB will have to flex with the load. This is one of the big advantages of the M4T6 bridge type as it is designed to accommodate this flex.I wonder what union gets this job?Photo #4 is a BB and pontoons. This was done at a demo in the WWII frame. Notice how much stronger the BB sections are and the crown in the bridge.Photo #3 shows the flex of a BB and pontoons as a light tank crosses.Photo #2 shows an M4T6 bridge in Argentina built by Americans. Notice how close the pontoons are and that the treadway is flexible.Photo #1 shows the arc in the chord of the bridge from the current pushing it downstream. The boat is in place to push back in case an anchor line breaks or a big piece of debris comes floating down. https://uploads.disquscdn.chttps://uploads.disquscdn.chttps://uploads.disquscdn.chttps://uploads.disquscdn.c…JLMwww.themusingsofthebigredca…

    1. fredwilson

      you and my dad said essentially the same thing about the drawbridge. this is what my dad said to me via email this morning:”I suppose that it would be possible. It would be a mechanical marvel, and I’d like very much to see it after it’s built.Instead of a drawbridge, perhaps it would be better to make a section of the temporary bridge so that it could be swung open sideways.”

      1. JLM

        .Great minds.A decent combat engineer battalion with a bridge company (always Co E) could build this baby in less than a week if all of the materials were on site.When I set the record in Korea, I built the bridge parallel to the river bank. That way, I could use cranes to swing things into place. Build the sections on land and swing them into the water, then hook them up.Then, I swung the bridge into the width of the river using bridge boats. The bridge boats held it in place until we got the cables installed to hold it.I developed a field expedient of crossing a couple of dozers to the far side. When we measured the width of the river, I’d build the bridge 10′ shorter and then use the dozers to extend the abutments on each end.Getting the length right is always the big problem. It is hard as hell to measure a river’s width. Today, they do it with lasers and GPS.I have a light April in case NYC needs me to come slap that bridge into place.JLMwww.themusingofthebigredcar…

  11. William Mougayar

    Very creative project. How long would it take to build such a temporary bridge?

  12. Benjamin Kabak

    How utterly dismaying to see otherwise smart people lining up behind an idea with no technical merit and even less transportation merit. Spanning an extremely volatile East River with substantial pre-existing marine traffic with a bridge that won’t address mitigation for the vast majority of L train riders and when there’s already a pre-existing bridge a few city blocks away is completely unrealistic and a distraction from the real battle over the mitigation plans currently being waged by transit advocates, policymakers and community boards. George Parker though would be quite proud.

  13. jason wright

    they should have just built a new tunnel first.

  14. Pointsandfigures

    Did Dad build that bridge for a General Patton? (Patton might have taken a leak off your dad’s bridge!) http://www.lostimagesofww2….

  15. sigmaalgebra

    You have good engineering judgment about floating bridges? Nope. You have a good father? Yup!!!!