Huntington Ave. signal priority/preemption

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

Moderators: CRail, sery2831

Postby CSX Conductor » Fri Dec 17, 2004 9:19 pm

First I have heard of it, but the technology is quite possible. (Especially with Wentworth being trackside, LOL) :P

I rememer reading that the CDTA (Capital District Transit Authority) buses in Albany Ny were being outfitted with a "jump-start" system that would give the bus an earlier signal as to allow it to pull away from the curb without having to wait for other traffic.
User avatar
CSX Conductor
 
Posts: 5458
Joined: Fri Mar 12, 2004 12:04 am
Location: Boston, Mass

Postby efin98 » Fri Dec 17, 2004 9:35 pm

Could be a test run of the system, might be limited only to the shortest line for now until the T can analyse the results for future expansion to the other three lines and the bus system.
But they also might be mistaking the sensor for signal priority with the sensors for the Type 8s and modified Type 7s that trigger the automatic stop announcements.
efin98
 

Postby vanshnookenraggen » Fri Dec 17, 2004 9:41 pm

CDTA!! Oh my god does that bring me back! Yet another system looking at BRT.
Back on track (no pun intended), how long have those sensors been there? I'd like to see how those work out.
vanshnookenraggen
 

Postby BC Eagle » Fri Dec 17, 2004 10:03 pm

If they introduced these on the B-Line, it would easily take 10 minutes of the trip. Possibly even more. I'm not holding my breath though.
BC Eagle
 

Postby StefanW » Sun Dec 19, 2004 12:57 pm

There have been sensors on the B line for a long time. They are visible between the rails at most grade crossings between BU West and Chestnut Hill Ave (and maybe all the way to BC - I don't recall that stretch).

They are embedded in concrete slabs between the rails, about 2' x 4', usually with a single small wire leading out to a metal in-ground box with a cover that says MBTA or BTD (Boston Transportation Dept.) or sometimes "Mass Highway". Since it's a single wire, it seems to be an inductive loop sensor just like what's embedded in the asphalt to detect autos at most intersections. The old AVI antennas / pickup loops were just wires caulked into wooden frames which are now all gone, but the traffic signal pickups remain.

The boston.com article says:
where BTD controls signals on two pieces of the road -- from Kenmore to the BU Bridge and from Warren Street to Lake Street

...but I disagree. There aren't any left between Kenmore and the bridge, except for one on the outbound side right at the Route 2 crossing and one that's sitting idle outside the inbound rails by Guitar Center. (That one got pulled out during the BU Central station rebuild and never put back.) Also, there are lots between BU West and Warren St., but perhaps are not hooked up.

Whether or not the pickup of a trolley by the sensor actually works is up to the BTD. It would have to be programmed into the signal control computer at each intersection whether or not to act on the presence of a trolley.

A side note: the ID tags that are used by the station announcement system are visible usually 25 yards or so before and usually after a station, right between the rails. Look for a small plastic box mounted on a crosstie, about the size of a cigarette lighter, with a printed label that has the stop name on it. I'm quite certain they are RFID tags similar to the MassPike FastLane transponders.
User avatar
StefanW
 
Posts: 477
Joined: Wed Aug 18, 2004 8:27 pm
Location: Lynn, MA / MP 11.53

Postby BC Eagle » Sun Dec 19, 2004 1:44 pm

I think it's insane that these sensors exist on the B-Line and are not in use.
BC Eagle
 

Postby StefanW » Sun Dec 19, 2004 2:13 pm

I think it's insane that these sensors exist on the B-Line and are not in use.


I don't know that they are not being used. I can only say that they don't seem to be putting any priority on getting the trolleys through ahead of autos. Maybe the E line sensors cited in that boston.com article are all the same hardware as on Comm Ave, but the programming of the signal computers is more modern...
I'll have to take a trip down Huntington to see what's there.

Oh, one time I was waiting at Chestnut Hill Ave for a B train when a BTD guy was working in the traffic signal control box. I took a peek: there were lots of electronics, and an interface board w/LED indicators for each lane loop sensor - and I believe there was one for each trolley pickup, clearly labelled.
User avatar
StefanW
 
Posts: 477
Joined: Wed Aug 18, 2004 8:27 pm
Location: Lynn, MA / MP 11.53

Postby BC Eagle » Sun Dec 19, 2004 6:34 pm

I ride the B-Line rather regularly, and I've seen no evidence of sensors being used to give the trolleys signal priority.
BC Eagle
 

Postby efin98 » Sun Dec 19, 2004 9:08 pm

BC Eagle wrote:I ride the B-Line rather regularly, and I've seen no evidence of sensors being used to give the trolleys signal priority.


How could you have known where to look or what to look for, you just found out they were there...
efin98
 

Postby BC Eagle » Sun Dec 19, 2004 9:39 pm

efin98 wrote:
BC Eagle wrote:I ride the B-Line rather regularly, and I've seen no evidence of sensors being used to give the trolleys signal priority.


How could you have known where to look or what to look for, you just found out they were there...


That doesn't stop me from noticing that the trolleys stop for red lights on Commonwealth Ave. Especially since it happens so often.
BC Eagle
 

Postby octr202 » Sun Dec 19, 2004 9:47 pm

Although I don't know if its stil up there, CTPS at one time had a report on its website that was a study of the US Route 20 corridor from Boston to Waltham, which includes Comm. Ave. between Kenmore and Packards Corner. That report mentioned that trolley preemption equipment was installed (in the 1980's IIRC), but was never activated on account of an inability of MassHighway, BTD, and the MBTA to agree on the timing of cycles. The report in fact stated that the equipment had just been left to disintegrate in the field and was virtually useless. If I can find the link tomorrow at work I'll add it here.
Wondering if I'll see the Haverhill double-tracking finished before I retire...
Photo: Melbourne W7 No. 1019 on Route 78, Bridge & Church Streets, Richmond, Victoria. 10/21/2010
User avatar
octr202
 
Posts: 4142
Joined: Fri Mar 12, 2004 8:13 am
Location: In the land of the once and future 73 trackless trolley.

Postby efin98 » Sun Dec 19, 2004 11:04 pm

BC Eagle wrote:
efin98 wrote:
BC Eagle wrote:I ride the B-Line rather regularly, and I've seen no evidence of sensors being used to give the trolleys signal priority.


How could you have known where to look or what to look for, you just found out they were there...


That doesn't stop me from noticing that the trolleys stop for red lights on Commonwealth Ave. Especially since it happens so often.


You are noticing that the trolleys stop alot, but you don't know if they are going with the signals naturally or if they have help from the censors. Until you were told by the article and the forum you didn't even know they existed.
efin98
 

Postby BC Eagle » Mon Dec 20, 2004 1:45 am

efin98 wrote:You are noticing that the trolleys stop alot, but you don't know if they are going with the signals naturally or if they have help from the censors. Until you were told by the article and the forum you didn't even know they existed.


Thanks for telling me what I know, and what I don't know, but it's common sense that if the trolley is spending several minutes at the majority of traffic lights along Comm. Ave. there are no sensors providing priority to the trolleys. Also, one can see from simple observation that the trolleys follow the natural cycle of the traffic lights on this route. I did not know about the sensors, because there is no evidence whatsoever that they are in use.
BC Eagle
 

Postby StefanW » Mon Dec 20, 2004 6:08 am

BC Eagle wrote: ...if the trolley is spending several minutes at the majority of traffic lights along Comm. Ave. there are no sensors providing priority to the trolleys. Also, one can see from simple observation that the trolleys follow the natural cycle of the traffic lights on this route. ...


Bear in mind that simple inductive-loop sensors between the rails can't ever send the kind of message to the traffic signal computer that the BTD would probably insist on having for a trolley-priority model.

For instance: As we all know the "BU Shuttle" can get really bogged down with heavy ridership, resulting in long waits at a stop during boarding. There might be a serious negative impact on auto traffic if every time a trolley reached a grade crossing all the lights for autos went red, only to have the train sit for minutes while boarding finishes.

The only really good solution I can imagine is manual operator-controlled signalling instead of sensors - much like the Ipswich crossing on the CR. Have you seen this? I think it's very elegant.

The arriving northbound CR train into Ipswich station does not start the crossing gates automatically, even though the train comes to a stop feet from the crossing. The engineer has to throw a high-mounted switch before the gates will activate.

Now, I'm not suggesting Green Line operators should open their windows and reach for a switch (as that wouldn't help the all-too-familiar "express" run) but instead something like AVI signalling - radio sent from the trolley to a track-mounted antenna - would work. The operator could toggle a panel switch which would send an indication to the BTD computer that the trolley was actually ready to proceed.

I think it's too bad that all the AVI sites above-ground on the B line were ripped out (from what I can see) as that would have made a good traffic signal interface.
User avatar
StefanW
 
Posts: 477
Joined: Wed Aug 18, 2004 8:27 pm
Location: Lynn, MA / MP 11.53

Postby octr202 » Mon Dec 20, 2004 8:45 am

From the 1998 CTPS Route 20 Transportation Planning Study:

Green Line B Branch Signal Priority System
Traffic congestion and traffic signals cause significant delays for Green Line transit
service in the study area. The Green B Branch passes through 11 signalized intersections over its
1.4- mile stretch along Commonwealth Avenue. These 11 signals have semi-actuated controls
that return any unused green time on the cross streets to the arterial (Commonwealth Avenue).
To provide more efficient service for the Green Line, a signal priority system was installed to
give priority to the trolleys at the intersections.
At the moment, this priority system is inoperative. Most of the equipment has broken
down or is missing in the field. The present status of the equipment is documented in Appendix
C of this report. Currently, the trolleys have no priority, sharing signal phases with the
automobiles on Commonwealth Avenue. This has resulted in poor performance and also longer
travel times, making the Green Line B Branch an unattractive mode compared to the automobile.
It is estimated to cost $82,000.00 to replace the broken and missing equipment according to an
assessment study conducted by LS Transit System.


The whole report is at: http://www.ctps.org/bostonmpo/resources/cmsrt20.pdf

The above comes from report page 58. Section 5.3.2 (Page 139) starts with the discussion the modelling done to test whether signal prioritization would do any good. I only skimmed the section, but it appears that they claim that prioritization would only reduce running times by about 10%. Interestingly, putting near side platforms in (i.e., before the intersection) would reduce running times by 20%.
Wondering if I'll see the Haverhill double-tracking finished before I retire...
Photo: Melbourne W7 No. 1019 on Route 78, Bridge & Church Streets, Richmond, Victoria. 10/21/2010
User avatar
octr202
 
Posts: 4142
Joined: Fri Mar 12, 2004 8:13 am
Location: In the land of the once and future 73 trackless trolley.

Next

Return to Massachusetts Bay Transportation Authority (MBTA)

Who is online

Users browsing this forum: Yahoo [Bot] and 7 guests