Silver Line to Chelsea

Arlington said:
and/or add an exit ramp/tunnel from the westbound I-90 to Silver Line Way.

Before I-90 opened, the TWT had a temporary up-ramp there (I think to D St?)
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It did, but according to Google Earth historic imagery, the ramp was sunk into part of I-90W. The whole footprint is now the trench.

I don't think you can do a ramp there without making serious changes to the highway retaining walls or tearing down the Manulife building.
 
Joel N. Weber II said:
However, I think the proposal there to buy more trolleybuses is the wrong approach; I think we should go with batteries instead at this point. It's nearly always useful to be able to run routes beyond where it's convenient to install the overhead wires.

Why doesn't the article propose to change the way the D street light works to give the buses more priority?
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AFAIK, the current D St light does have signal priority enabled, although not as aggressive as possible. However, in a future scenario with increased frequency, it becomes difficult to move enough buses through the light. Only 2 buses can clear per green light, so if bunching means you ever have >2 vehicles queued at the light, no matter what priority you give you wind up with a permanent 1 cycle backup.
 
FitchburgLine said:
AFAIK, the current D St light does have signal priority enabled, although not as aggressive as possible. However, in a future scenario with increased frequency, it becomes difficult to move enough buses through the light. Only 2 buses can clear per green light, so if bunching means you ever have >2 vehicles queued at the light, no matter what priority you give you wind up with a permanent 1 cycle backup.
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There is a lot more flexibility to the capacity than that. You are assuming for some reason that they can't increase the length of the busway green phase. Set it with a short minimum green for D-street and a max time equal to the realistic max number of buses that would be queued up. This costs $0, the only reason it's not like that already is that whoever controls the signals is too focused on delay for cars on D.
 
chmeeee said:
There is a lot more flexibility to the capacity than that. You are assuming for some reason that they can't increase the length of the busway green phase. Set it with a short minimum green for D-street and a max time equal to the realistic max number of buses that would be queued up. This costs $0, the only reason it's not like that already is that whoever controls the signals is too focused on delay for cars on D.
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The current setup both has operational signal priority and manages the current frequency without endless queuing. If we're keeping the SL at roughly current service, TSP is all that should be done. However, it's not crazy to expect large increases in service levels, and if you want to do aggressive TSP, solo buses in each direction get a light change, which means 60 SL phases per hour or more (30bph/direction is reasonable for peak load on SL1/2/3). That's probably still doable on the surface, but its way more than any rail grade crossing in the US, and probably more aggressive than any other TSP installation.
Edit:
LA is considering spending 200-300m on grade separations for the Orange Line BRT. Its current schedule (https://media.metro.net/documents/7a394b30-751b-43b4-a8a2-f61e08ee174e.pdf) shows peak headways of... less than the Silver Line today.
 
FitchburgLine said:
The current setup both has operational signal priority and manages the current frequency without endless queuing. If we're keeping the SL at roughly current service, TSP is all that should be done. However, it's not crazy to expect large increases in service levels, and if you want to do aggressive TSP, solo buses in each direction get a light change, which means 60 SL phases per hour or more (30bph/direction is reasonable for peak load on SL1/2/3). That's probably still doable on the surface, but its way more than any rail grade crossing in the US, and probably more aggressive than any other TSP installation.
Edit:
LA is considering spending 200-300m on grade separations for the Orange Line BRT. Its current schedule (https://media.metro.net/documents/7a394b30-751b-43b4-a8a2-f61e08ee174e.pdf) shows peak headways of... less than the Silver Line today.
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This is not a rail crossing. 60 crossings per hour would be one per minute. Plenty of signals in the metro Boston area operate on cycle lengths of ~60 seconds.

Also, it doesn't need TSP, that's just excessive technology for a dedicated busway. Complicated signal communication between a bus and a signal is good for when they're mixing with general traffic so that the signal can know that a bus is coming and give it priority. When the buses are the only vehicle on the side street approach, all it needs is advance detection. Detector 200 feet down from the signal picks up a bus, sends a call to the controller. No communication with bus needed.
 
I have always wondered: is there a good/engineering reason that when it was built, the tunnel had to surface at D Street instead of extending it ~500' so it would be completely grade separated? Would the building and/or its foundation there prevent this from happening at some point in the future?
 
chmeeee said:
This is not a rail crossing. 60 crossings per hour would be one per minute. Plenty of signals in the metro Boston area operate on cycle lengths of ~60 seconds.

Also, it doesn't need TSP, that's just excessive technology for a dedicated busway. Complicated signal communication between a bus and a signal is good for when they're mixing with general traffic so that the signal can know that a bus is coming and give it priority. When the buses are the only vehicle on the side street approach, all it needs is advance detection. Detector 200 feet down from the signal picks up a bus, sends a call to the controller. No communication with bus needed.
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None of those signals have absolute priority (again, are you just calling for a green extension/red shortening system? That already exists). The SL should have the same standards as a metro, since it's serving similar demand, and international examples of tramways e.g. in Paris use absolute priority, then grade separations.
TSP isn't a technology dependent term. The Green Line uses "TSP" yet doesn't need to distinguish between general traffic and trolleys.
 
chmeeee said:
There is a lot more flexibility to the capacity than that. You are assuming for some reason that they can't increase the length of the busway green phase. Set it with a short minimum green for D-street and a max time equal to the realistic max number of buses that would be queued up. This costs $0, the only reason it's not like that already is that whoever controls the signals is too focused on delay for cars on D.
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Like maybe 20 second minimum green time for traffic on D street?
 
Arlington said:
and/or add an exit ramp/tunnel from the westbound I-90 to Silver Line Way.
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I think the right way to accomplish a rough approximation of this may be to have the South Station bound buses coming from the Ted Williams Tunnel skip the Silver Line Way and WTC stops, and have a new exit / portal so that those buses can go under the B St / Congress St intersection to get into the bus tunnel. There does seem to be space between the I-90W off ramp and the I-90W on ramp.

Alternatively, bring the buses up to grade at the B St / Congress St intersection, and have a new portal / ramp from that intersection heading down into the tunnel.

All of this is easiest if we can get buses with long enough range batteries that we don't need the overhead power lines.
 
jass said:
You can couple rubber tired vehicles just fine
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My understanding is that double and triple trailers have to be very careful to not change lanes quickly when traveling along the highway.

Double articulated ~80' buses do exist, but AFAIK not in the US.
 
Joel N. Weber II said:
All of this is easiest if we can get buses with long enough range batteries that we don't need the overhead power lines.
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The MBTA is putting a lot of thought into that - I watched the FMCB livestream where Sec. Pollack was discussing a lot of details of battery bus procurement (not a mature technology, not enough vendors, lots of single-bus pilots but very few large procurements), though since it's not in any slides it would be far too much effort to find the video in the archive.
 
FitchburgLine said:
None of those signals have absolute priority (again, are you just calling for a green extension/red shortening system? That already exists). The SL should have the same standards as a metro, since it's serving similar demand, and international examples of tramways e.g. in Paris use absolute priority, then grade separations.
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I'm calling for a short minimum green time on D so you don't have situations where buses have to wait a minute plus to get across. They don't need absolute priority, life will go on if they have to wait 10 seconds because they arrived 10 seconds after the phase switched for the previous bus.

TSP isn't a technology dependent term. The Green Line uses "TSP" yet doesn't need to distinguish between general traffic and trolleys.
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It's typically used that way and generally implies new equipment.
 
Equilibria said:
The MBTA is putting a lot of thought into that - I watched the FMCB livestream where Sec. Pollack was discussing a lot of details of battery bus procurement (not a mature technology, not enough vendors, lots of single-bus pilots but very few large procurements), though since it's not in any slides it would be far too much effort to find the video in the archive.
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In the 40' category, how is Proterra + New Flyer + BYD not enough vendors?

Worcester's Proterra fleet is 6 buses AFAIK, which doesn't really sound like a single bus deployment.

Was Stephanie able to describe actual problems the Proterra deployment in Worcester has had that don't have straightforward solutions? (I think Proterra is now offering much larger battery capacities than they did when the Worcester buses were ordered.)

AFAIK Proterra doesn't have a 60' bus yet, and New Flyer seems to be not rapidly making them, but AFAIK BYD is prepared to sell ~60' buses.

I'm certainly happy to wait a year or two on making decisions about what we're actually doing about improving the I-90W to South Station situation to see how battery bus technology improves, as long as the section of tunnel under the parking lot between Seaport Blvd, Congress St, B St, and E Service Rd doesn't get a building on top of it or immediately next to it that takes away the opportunity to build a new portal...
 
Joel N. Weber II said:
In the 40' category, how is Proterra + New Flyer + BYD not enough vendors?

Worcester's Proterra fleet is 6 buses AFAIK, which doesn't really sound like a single bus deployment.

Was Stephanie able to describe actual problems the Proterra deployment in Worcester has had that don't have straightforward solutions? (I think Proterra is now offering much larger battery capacities than they did when the Worcester buses were ordered.)

AFAIK Proterra doesn't have a 60' bus yet, and New Flyer seems to be not rapidly making them, but AFAIK BYD is prepared to sell ~60' buses.
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All of those would be excellent questions to ask her :) Sadly, my memory is far from perfect.
 
chmeeee said:
I'm calling for a short minimum green time on D so you don't have situations where buses have to wait a minute plus to get across. They don't need absolute priority, life will go on if they have to wait 10 seconds because they arrived 10 seconds after the phase switched for the previous bus.
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What's the best way to handle the pedestrian crossing signals across the busway? Would we be better off making it work like the crosswalk across the busway at College Ave in Davis Sq in Somerville where there is no pedestrian signal?
 
One of the snags with changing the signal at D is that there are closely spaced signals at D's intersections at Congress, Haul, and Summer. All of these are coordinated. There is some hesitation because of the impact that giving the busway more time has on the entire network of intersections.

I know the departments (BTD, MBTA, MassDOT?) meet at least monthly to discuss TSP and they have plans to implement them (in "places"), but I do not know why it has taken years to make changes.

If the D Street signal operated in isolation then this would be very straightforward.
 
Equilibria said:
The MBTA is putting a lot of thought into that - I watched the FMCB livestream where Sec. Pollack was discussing a lot of details of battery bus procurement (not a mature technology, not enough vendors, lots of single-bus pilots but very few large procurements), though since it's not in any slides it would be far too much effort to find the video in the archive.
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We really need to look outside the US for experience in this topic.

Every major city in China has huge battery electric bus fleets. We are buying Chinese train sets for the Red and Orange Lines, why not Chinese busses.

BYD has extensive experience in this area (battery electric busses). Shenzhen now has 14,000 (that is NOT a typo) electric buses, a 100% battery electric fleet, 80% supplied by BYD. The "not enough experience, not any large fleets" is a retrograde US canard (meaning BS).

https://cleantechnica.com/2017/11/12/100-electric-bus-fleet-shenzhen-pop-11-9-million-end-2017/
 
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