• MBTA Bus Fleet Electrification

  • Discussion relating to commuter rail, light rail, and subway operations of the MBTA.
Discussion relating to commuter rail, light rail, and subway operations of the MBTA.

Moderators: sery2831, CRail

  by scratchyX1
 
Just curious , How come Pantographs haven't replaced trolly poles on rubber tire electric buses (like they have on some eastern European trucks)?
  by Disney Guy
 
Pantographs will work only when the vehicle is constrained to a single lane of travel. Which might work okay for some bus rapid transit situations.

Otherwise the pantographs will go out from under the wires as the vehicle changes lanes, that is, the pans will dewire.

Now I suppose we could have multiple parallel wires say 5 feet apart alternating positive and negative and the pan switches to another wire as the vehicle changes lanes anywhere along the route. But the pan has to leave one live wire before going under the next live wire* to prevent a short circuit and the result will be a momentary loss of power which is not good.

* The parallel wires would actually be something like positive, dead, negative, dead, positive, dead, etc. and the dead wires keep the pan shoe on the level to go under the next live wire when changing lanes but we still have the problem of momentarily loss of power.
  by BandA
 
Mt. Auburn St is not wide enough for dedicated bus lanes. You really need a 6-8 lane arterial road to justify dedicated bus lanes.
  by Disney Guy
 
Even though it is not as good, a substantial improvement in bus operation can be had with a labeled non-exclusive lane. The words "BUS LANE" need only be painted a few feet in advance of each stop and at the stop proper there would be a rectangle about the size of the bus painted in the travel lane to let passengers know where the bus will stop and they would walk out to the bus or wait in the space just off the curb. This would simplify bus maneuvering. Also the trolley wires could be hung a little further out giving the bus more maneuvering range if needed e.g. there is a double parked car or other obstruction. This would only need a 4 lane road as a minimum.
  by octr202
 
Mt. Auburn is largely two lanes in each direction, despite not having that high a volume of traffic. The street could likely function just fine as a two-lane street with turn lanes at the major intersections.

Belmont & Trapelo were largely similar, and several sections were cut down to one lane each way without a severe impact.

That said, the approach being taken is the right one - queue jumps at key intersections, priority signals to allow buses to get a green ahead of other traffic, and dedicated lanes where frequent backups occur, such as was done on the Cambridge portion of the route.
  by caduceus
 
Are there any two-wire (pos/neg-ground) pantograph systems anywhere? I couldn't find any examples. Electric trains use the rails as the electric return to complete a circuit.

It seems like a hybrid wire-battery system would be good - have enough power if the poles de-wire to safely get to a convenient point to re-wire the poles.

How much do they actually run the trackless these days? When I was frequenting the Porter/Harvard area while Kid#1 was living there for college, I think I only ever saw two running...and one of them de-wired. I saw far more regular buses on the route.
  by MBTA3247
 
There are several 3-phase AC systems, which use two wires and the rails.

Porter Square sees relatively few TTs, as they only use it when going to/from the North Cambridge Carhouse.
  by ExCon90
 
scratchyX1 wrote: Thu May 06, 2021 12:38 pm Just curious , How come Pantographs haven't replaced trolly poles on rubber tire electric buses (like they have on some eastern European trucks)?
It may be because on curves a long trolley pole will follow the wire while a pantograph follows the body of the vehicle and will come off the wire if the vehicle doesn't make a precise turn.
  by chrisf
 
Disney Guy wrote: Thu May 06, 2021 1:33 pmThe parallel wires would actually be something like positive, dead, negative, dead, positive, dead, etc. and the dead wires keep the pan shoe on the level to go under the next live wire when changing lanes but we still have the problem of momentarily loss of power.
The dead wire will be energized when the pantograph makes contact with it while still in contact with live wires.
Pantographs would be pretty much impossible to use on trolley buses due to the need for two wires.
  by Rabid Transit
 
Someone brought up the fear of battery buses catching fire. According to a brief weg search It appears MBTA buses have already caught fire from time to time due to one issue or another, so what 's the difference?. :-) If the T aims to eventually replace all buses with battery power, then what's the point of retaining the older trolleybus system?


Sierra Club's take on the MBTA's apparent slow conversion from conventional buses to electric:

https://www.sierraclub.org/press-releas ... -pollution


This article debunks EV myths:

https://www.insideevs.com/features/3883 ... cle-myths/


Bear in mind that there once was a time when the internal combustion engine itself was in development, and that critics didn't think it would ever amount to anything. In time gas engine technology became more reliable and the infrastructure (gas stations etc) grew to support it. Battery tech is constantly improving, and the power grid also continues to adapt to increase in demand.
  by TurningOfTheWheel
 
As I've stated, I think the reliance on an exclusively battery fleet is short-sighted in practical terms. Replacing the trolleybus network with batteries is going to be a lot harder than the T is selling here. It seems much more operationally and energetically efficient to invest in overhead wires that will see continuous use throughout the day rather than several hundred charging stations that require buses to leave service to charge. Again, I would advocate for an expansion of the trolleybus network, in-motion charging trolleybus/battery systems where applicable, and exclusively battery buses only where it's strictly necessary. The operational advantages of the trolleybus system (especially with expansion and modification to accommodate in-motion charging) make it an asset worth keeping around.
  by typesix
 
Rabid Transit wrote:Someone brought up the fear of battery buses catching fire. According to a brief weg search It appears MBTA buses have already caught fire from time to time due to one issue or another, so what 's the difference?.
The lithium batteries can have severe fires if they start burning, some special techniques have to be used to fight lithium fires. Even after the initial fire is put out, a watch over the batteries have to be performed as the fire can start up again. Also, lack of experience with this type of fire by most fire departments as opposed to gasoline or diesel fire.
  by west point
 
Atlanta always called them tracks trolleys. Had them for many years as they worked with the street car overhead wires as I have been told.