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Saturday, July 3, 2021

The Reason The Boring Co Will Win (That No One Understands)


The Boring Company recently unveiled the Las Vegas Loop. Riders will use an app and select their destination. The app will direct them to a stall number and car; riders pile in and they are whisked off to their destination.

Currently, the cars are human-piloted and only driving at a max of 35 MPH. This, of course, was trumpeted by the Musk detractors. The criticism goes something like this: A car can only hold a few people; a train would hold many more. So, they conclude, install the track and make it a tried and true subway like so many other cities have. This would work much better.

I find this trains-thinking to be stuck in the 1900s. You might even say, they have "tunnel-vision." I'll explain.

Centralized vs Decentralized

Long ago, my day job was as a network engineer. I worked at a company developing network infrastructure products. We analyzed traffic flows (network packets) and methods to reduce latency and optimize throughput. We had contracts with NASA, The Olympics, most of the hyperscaler datacenters, and most of the server OEMs. The network traffic analysis I did there was not the same as automobile traffic, but there were some important lessons. When I started Token Ring was the cash cow, but things changed quickly.

Token Ring

This type of network is not all that different from a train route. Without going into the technology, nodes on this type of network are logically organized into rings. A circulating token controls access. This is not all that different from a train going around a loop, you can only get on the network/tracks when the train/token arrives. The nodes in this type of network are even called stations. This type of network eventually failed because it was not scaleable. As more nodes were added to the network, the effective throughput of any given station slowed. 

Ethernet (Half Duplex)

The technology that succeeded Token Ring was half-duplex Ethernet. This type of network allowed many more stations to be added to the network without choking throughput (with caveats). During those half-duplex days, networks had limited uses. On half-duplex networks, all of the nodes share a common communications media called the bus. Half-duplex networks function well when there are just a few, short-lived, traffic flows; which is why they worked well back then when most network traffic was periodic client-server activity (like fetching email or printing a document). However, as network communication became more essential with the rise of the internet and streaming, this type of common bus network collapsed under the pressure. This is like a walkie-talkie network with everyone on the same channel. You can have as many people as you want on that channel as long as most people are just listening most of the time; however, as soon as everyone wants to start talking frequently, you just have a jammed-up unusable bus. 


Switched Ethernet

We've looked at two network types (Token Ring and half-duplex Ethernet) that didn't scale (albeit for different reasons). Both of these technologies had a centralized control (the ring or the bus). Half-duplex Ethernet was quickly replaced by Full-duplex or Switched Ethernet. With switched Ethernet, there was no bus, no shared walkie-talkie channel, every node has its own dedicated channel. When node A is talking to node B the traffic flows from A to B. If C and D are on the same network, the conversation between A and B generally does not interfere with the traffic between C and D. This is the technology that is used today in everything from your home network to massive datacenters around the world. It is far more scalable and has much less congestion.  

So why didn't we just start here? The idea of switched networks has been around since the 1960s. The problem was the technology. At the heart of a packet-switched network is a switch that must look at every packet that comes in, determine its destination, and then send it out of the switch via the exact right port for that packet's destination. Multiply this by every port on the switch that is both and sending and receiving.  Then grow the network by having switches attached to other switches, path discovery, forwarding tables... the switches that allow this type of network to be possible have to be very advanced.

During the time that Token Ring and half-duplex, these full-duplex switches would have been very expensive (if even technically possible).

Comparing Network Topologies to People Mover Topologies

So let's tie this back to the topic at hand, The Boring Company Loop system. 

Token Ring is like the train or subway. It has a fixed route and the more stops you add, the more people can access it, but the slower the overall speed. More throughput means more latency (i.e., longer travel time).  

Half-duplex is like a bus. If you charter a bus and your whole party is going to the same place, it works great. But if you have a bunch of people getting in all with different agendas, things fall apart quickly.  

The Boring Company's Loop design is a switched network. Riders select their destination and are assigned a dedicated car. That car goes to their selected destination directly. They don't stop at all the points in between to allow people in and out of the car. The Loop system computes the most effective route for your car to your destination. There's no stopping along the way.

The Boring Company's solution allows new routes and stations to be added to the network without adding interim stops at which all passengers must stop even when this is not their destination. 

This is a scalable transportation network. And it will get faster. 


Switched Ethernet started out at a speed of 10 megabits per second (Mbps). This grew to 100 Mbps, then 1000 Mbps or 1 gigabits per second (1 Gbps), then 10 Gbps, 100 Gbps, and now 800 Gbps is under development. I'm not saying that the vehicles in these tunnels will be 80 thousand times faster than their current 35 MPH speed, but they can get 3 or 4 times faster in long straightaways. To be fair, even at 35 MPH, this is far faster than city street traffic. With the stop and go of traffic lights and congestion, city traffic averages about 14 MPH door to door. So even the initial Loop speed is more than twice the speed a taxi / ride-share could offer (although with more limited destination options). 

Today, the cars in the narrow Loop tunnels are piloted by humans. This will change soon. Solving self-driving in this controlled environment will be far easier than solving it in city street driving. As regular readers know, our prediction is that Level 5 driving will not be solved until 2027. These tunnels, on the other hand, are the best case for self-driving. They don't have to deal with rain, snow, sun directly in the lens, cross-traffic... This Level 4 solution could launch as soon as 2022. 

Scale-out vs Scale-up - How TBC Wins

Trains scale by going faster, adding more train cars, and/or more stations/stops. This is scaling up. There are limits to increasing the speed and limits to adding more cars. As the number of stations increases, it increases capacity and access at the expense of increasing the average travel time for everyone using the platform. Scaling up trains quickly hits real physical limits.

The Boring Company scales by adding more destinations, more tunnels, and more cars. This is scaling out and it allows for more parallel operation. It means that stations, routes, and cars can be added to increase capacity without impacting the throughput or latency of the existing routes. It also means that popular stops can increase capacity by adding more ingress/egress tunnels to/from that station, thereby forming superstations. Alternatively, popular locations could have multiple standard-sized stations (e.g., Convention Center North Station and Convention Center South Station). This is easy to do with the Loop system since additional stations don't burden the system.

Scalability Adds Flexibility

If you add a stop on a train route that has low utilization, then you've slowed down everyone for the benefit of a few, if any, passengers. Similarly, if you add a bus stop in an out-of-the-way place, you add cost for the bus to periodically drive past this location, even if no one is getting on or off the bus. 

This is different with Loop. All rides are point to point. If a hotel or casino that has low traffic pays for a station, then the network has grown and no one has been slowed down and there is no on-going fuel cost to drive to this out-of-the-way location unless it is actually needed. 

I've avoided diving into the network analysis (graph theory) math for this article; instead, trying to articulate the common sense case. If you view each station as a vertex and each tunnel as an edge, there's a vast amount of analysis that can be done to understand the traffic flow within the system. The Boring Company will know every ride that occurs within the system. They'll be able to use graph theory and congestion information to determine the best paths for vehicles to take. 

If you have n number of stations, the possible number of station-to-station connections is n * (n-1). They'll be able to use historical information to determine the best path for each new tunnel that they add to the network. According to the Vegas Unzipped image above, there are 17 stations currently planned for the Vegas Loop. That's a possible 272 tunnels that could be dug for full-mesh connectivity. This would, of course, be overkill at the start of the system, but it demonstrates their ability to scale capacity as needed.

The Time Is Right

If this is clearly the best method for public transportation, why hasn't it always worked this way? The answer is the same as it was for Switched Ethernet: technology. Imagine if everyone that got on a train told the engineer where they wanted to go and then the route was computed and the tracks were switched in real-time. That wouldn't have been possible with last century technology. Today, however, route planning is trivial. 

Next on our 'the time is right' list is EVs. When a tunnel is designed exclusively for EVs, it doesn't need elaborate ventilation systems. Tesla's EVs will have the range to have a full day's service. They have the performance to whisk you at speed quickly to your destination. 

Our third item on this list is Apps. Today, nearly everyone has a smartphone, with the LV Loop app, you'll be able to schedule your ride and pay. The route will be calculated before you even click your seatbelt. There's no need to queue up to buy tickets... this is just another way that Loop systems will allow parallel operation.

Conclusion

Loop is in its beta phase, it will improve greatly over the next few years. As it matures, it will become the most efficient public transportation system we've ever built. This is not simply because it uses electric vehicles, it's because they have a significant technological advantage over the legacy competing technologies.

This is the same formula that other Musk Co. endeavors use. SpaceX's reusable rockets have a massive cost advantage over "disposable" rocket companies. Tesla's electric cars have a massive efficiency and performance advantage over their fossil-burning competition. 

The Boring Co. has "packetized" transportation and made a scalable "switched" network. This gives them a technological advantage over their last-century-based train competition. 

It's time to change from tunnel-vision to visions of tunnels.

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