By Noel T. Braymer
Elon Musk is primarily a promoter. He hires scientists and engineers to develop the cars, rockets, batteries, solar cells or what ever idea or project he is promoting. As a promoter he is an expert at teasing the public by releasing just enough information to spark their interest. But without to much information of what his intentions or what the status are for any of his many projects. This is particularly true with his Boring Company. He implies his company is working on a technological breakthrough which will create miles of tunneling costing much less than conventional tunneling and dug much faster than possible now which will be used to reduce auto congestion. There is plenty of history that shows adding more roads increases congestion, not relieving it whether on the surface, elevated or underground. So what are his short term plans for the Boring Company? I think he is working on a deal with the Los Angeles County Metropolitan Transportation Authority (LA Metro) to build a joint auto/transit bypass paralleling the 405 freeway. This would be part of a Public, Private Partnership with LA Metro. He is in contact with the Mayor of Los Angeles Eric Garcetti who is also a board member of LA Metro.
For some time Los Angeles County has been working on a plan to use a Public, Private Partnership to build a toll road tunnel between LAX and the San Fernando Valley as well as a mostly underground rail service also along the 405 corridor. Original planning called for revenues from tolls and fares to pay for these tunnels. The planning called for a large tunnel which would hold a double dock roadway for north and southbound traffic. A similar large tunnel over 57 feet in diameter started digging on July 30, 2013 for a 2 mile highway tunnel in Seattle. This massive tunnel boring machine got stuck by December 6, 2013. It was 2 years later before tunneling was resumed and it only finished tunneling on April 4, 2017. The actual tunnel won’t be finished now before 2019. Since these problems in Seattle, LA Metro was been rather quiet about any plans for tunnels along the 405 corridor. The reality is some of the heaviest traffic in Los Angeles is along the 405 between LAX and the San Fernando Valley. It also has the fewest options for using rail transit alternatives to replace driving north and south on the west side of Los Angeles County. There is great interest by people in Los Angeles County for alternatives to the 405.
So what do we know now about what the Boring Company is up too? They have been digging a 12 foot diameter tunnel using a used tunnel machine originally built to dig sewer lines on property owned by Elon Musk in Hawthrone, California .This is near the Hawthorne Airport where Tesla and Space X companies also controlled by Musk have offices. He recently received approval by the city to extend his tunnel by 2 miles to the west under city streets of Hawthorne. The plan of the Boring Company is to save money tunneling by digging smaller tunnels. A road or rail tunnel is usually 26 to 28 feet in diameter compared to the 12 foot diameter tunnel being dug by the Boring Company. A typical highway lane is only 12 feet wide. Only autos or small trucks will fit in this small tunnel. It is so small that it would be difficult for anyone to drive safely in these tunnels. What is planned is for cars to drive onto a wheeled platform called a “skate” when entering a car size elevator to reach the tunnel. The skate would carry the vehicle to its final destination in the tunnel and would most likely use Tesla Auto Pilot to navigate the skate in, through and out of the tunnel at speeds up to 125 miles per hour.
What is also planned by the Boring Company are the use of “pods”. These pods would be attached to skates to carry passengers and bikes in tunnels parallel to the 405. No information has yet been released on how big these pods are, how many people they could carry or where they would stop. Basically with these small tunnels, you would have one row of no more than 3 across seating and need doors for each row of seats with doors at both ends of the seat row much like a car. To carry many people at a time you would likely need a train of several skates and pods connected together. This might be something like the trams used at Disneyland to get people from the parking structures to the main gate. But even these tram cars are wider than your typical auto so they wouldn’t ft in a 12 foot diameter tunnel.
So how many cars can such a tunnel carry? According to a web site for traffic engineers a typical 4 lane freeway is expected to carry up to 72,000 vehicles a day. This about the average daily ridership of a busy light rail service. If divided by 4 that gives 18,000 cars per day per lane and 750 cars per hour on each lane. Now these results are averaged over 24 hours. So most freeway have much higher traffic during peak periods and lower traffic late at night. On a freeway lane a rate of 2,000 cars an hour is the most that can be achieved before traffic becomes congested bringing on stop and go traffic which greatly reduces a road’s capacity. With automated operation of the skates let’s assume service is accident and congestion free with up to 2,000 skates per hour in each direction. If half of the skates carry cars with 1.5 passengers that ‘s 1,500 persons per hour with 1,000 skates. If you carry 10 people in 1,000 pods every hour that’s 10,000 people per hour. There are 60 minutes in an hour which makes 3600 seconds in an hour. With 1,000 pods each carrying 10 passengers an hour that means a 10 passenger pod drives by every 3.6 seconds. What’s the shortest time at stops for a pod will it take to safely load and unload pods? Maybe 15 seconds if there are no problems.
How would pods or cars on skates get in and out of such a tunnel with skates only a few seconds apart? The solution in use since the 1930’s is to build acceleration and deceleration lanes or in this case tunnels to get on and off the main tunnel. The pod would start accelerating to fit in a slot between skates coming up to speed right behind the skate in front of it. These acceleration/deceleration tunnels will add costs to the construction of this project as well as increase the complexity of operations.
There are times when transit in heavily populated areas needs capacity of up to and greater than 10,000 passengers an hour. There are Light Rail services that can carry up to 20,000 passengers an hour and heavy rail even more. Los Angeles will continue to see transit rail service ridership grow as more lines are built or extended with more connecting together. Now a possible solution to carrying people with pods is to run pods that are express services. Instead of making all stops, you could be assigned a pod that stops where you are at and to where you want to go. This would be something like riding a smart horizontal elevator. Such schemes have been tried in the late 20th Century but none succeeded. Let’s see what it takes to carry 10,000 passengers an hour in pods with up to 50 passengers? That would require 200 pods an hour which would mean a pod every 18 seconds. That’s very convenient, but still cutting things tight. Even though the pod would be off of the main tunnel, the problem will be unloading and loading people and bikes in under 30 seconds. One late pod could disrupt service for several pods on a line for some time. What do you need to run pods every minute? You could carry 10,000 passengers an hour with pods carrying 167 passengers run every minute.You could also do that with a single light rail car. At least with larger vehicles there is more time for passengers to get to the platform and less of a rush to exit the pod.
Of course this is all conjecture since Elon Musk and his Boring Company hasn’t disclosed their plans of what they want to do with their pods or their skates. There is economy and simplicity is using fewer and longer vehicles. Fully automated light rail vehicles already exist and are in operation carrying comparable loads of people. Perhaps the biggest issue will be mixing traffic with auto skates and pod skates. The solution might be to dig 4 tunnels, 2 for autos and 2 for super large pods. But first we will have to see what is planned for this Boring tunnel project.