Automatic train protection on the Green Line?

Why does the green line have no trip arms or automatic train protection system unlike the other lines?

The Green Line is a streetcar line that has the most basic signal system possible. It's just a hold over from when service was mostly in the streets with other traffic. There really is no reason to upgrade with good supervision.

To elaborate on what sery said, "If it ain't broke, don't fix it".

Then there is the notion that a two or three car trolley consist is probably much easier to bring to a halt than an entire Orange or Red Line train. Come around a curve and spot a Type 8 idling on the track ahead of you? Apply the brakes and wait until it's gone. Come around a curve and see an OL consist in your path...yeeaaahhhh...not gonna be a good day.

(Not quite on topic)
Subway trains have brakes on all axles or wheels. So why would it take longer for a 6 car train (in Boston; 10 cars in NYC) to stop compared with a two car train (in Boston; single car in Cleveland?)?

(On topic)
The newest Green Line cars (post 1973) can go much faster compared with older cars (pre-1941). Maybe signal trip arms, etc. would be appropriate for the Green Line today.

>>> Come around a curve and spot a Type 8 idling on the track ahead of you? Apply the brakes and wait until it's gone.

Didn't that happen recently at Boylston inbound and they didn't quite miss? Anyway the second train must have come around the curve fast enough to throw the passengers to the side, which means going too fast.

Disney Guy wrote:(Not quite on topic)
Subway trains have brakes on all axles or wheels. So why would it take longer for a 6 car train (in Boston; 10 cars in NYC) to stop compared with a two car train (in Boston; single car in Cleveland?)?

Weight. A 50 car loaded coal train can't stop as fast as a 50 car train of empty flat cars. And each axle on those cars have brakes.

Disney Guy wrote:(Not quite on topic)
Subway trains have brakes on all axles or wheels. So why would it take longer for a 6 car train (in Boston; 10 cars in NYC) to stop compared with a two car train (in Boston; single car in Cleveland?)?

It's all about mass and inertia. The amount of inertia an object has is proportional to its mass. Newton's first law of motion is about inertia. Everything in motion remains in motion unless stopped by an outside force.

Picture this: a skateboard and an SUV are rolling down a hill. Using only your body, which would be easier to stop? Now, replace "skateboard" with "two streetcars", and replace "SUV" with "six subway cars". Clearly, it takes a significantly smaller amount of force to stop a Green Line train.

Due to their lack of mass, Green Line cars deaccelerate much faster than any other subway car in Boston. If they can stop so fast, then why would you need trip arms and ATO and all of that other fancy stuff? You also have to consider the fact that a portion of the E branch is street running. The trains run in automobile traffic. How would you install trip arms on the street? Why would the trains be cleared to run on the streets if trip arms are necessary to ensure a safe environment?

AznSumtinSumtin wrote:

Disney Guy wrote:(Not quite on topic)
Subway trains have brakes on all axles or wheels. So why would it take longer for a 6 car train (in Boston; 10 cars in NYC) to stop compared with a two car train (in Boston; single car in Cleveland?)?

It's all about mass and inertia. The amount of inertia an object has is proportional to its mass. Newton's first law of motion is about inertia. Everything in motion remains in motion unless stopped by an outside force.

Quite right, although the modern LRVs are actually pretty heavy. According to Wikipedia, a PCC weighs 25000 pounds, and according to a data sheet available at nycsubway.org, an R160 (which I'll use an example of a modern heavy rail vehicle) weighs 122000 pounds (and I'm not sure whether they're including or excluding the trucks in that). That's quite a difference. Unfortunately I was not able to find weights for a type 7 or a type 8 but I would guess it's something like 50000 - 75000 pounds, but riding on 6 axles (or, in the case of type 8s, 4 axles and 2 sets of stub axles ) instead of 4... so even in modern LRVs, load per axle is considerably lower than in a heavy rail vehicle. I believe that's not the only difference, though. I think that all the Green Line LRVs (and probably LRVs on other systems as well) have brakes (which are only used in emergencies?) that can be applied against the head of the rail as well as brakes that can be applied against the wheels. Also, I think (but again am not certain) that Green Line vehicles are equipped with sanders and heavy rail vehicles are not.

All modern rail vehicles for rapid/streetcar use have service braking rates of about 3.0 to 3.5 mph/sec-squared regardless of weight or whether it's one car or ten cars, since all the cars will act at the same time. Only PCCs which have not been reduced in braking rate will have a faster service brake. That rate is industry standard, as PCC rates are considered today to be supposedly too fast for standing passengers. Boston PCCs are about 40,000 lbs and the T7 and T8 are about 85-86,000 lbs.

sery2831 wrote:

Disney Guy wrote:(Not quite on topic)
Subway trains have brakes on all axles or wheels. So why would it take longer for a 6 car train (in Boston; 10 cars in NYC) to stop compared with a two car train (in Boston; single car in Cleveland?)?

Weight. A 50 car loaded coal train can't stop as fast as a 50 car train of empty flat cars. And each axle on those cars have brakes.

Freight trains and transit cars have much different braking systems, but the SMEE type systems on the bulk of the RT fleet is similar to that in the PCC cars. The P-Wire type systems in use on the 0700, 01800 and Green Line cars are also similar. This brake performance is not the issue. What matters is speed, which is enforced by the signal systems on the RT, but not on the Green Line, The performance of the cars today is better than the standard 25mph downhill with a tail wind of the older equipment. There is a tendency to go to fast, and the price is occasionally paid in the form of a rear ender.

The alternative is ATO on the Green Line, since trips would be impractical. That would cut the capacity of the central subway drasticly!

Gerry6309 wrote:The alternative is ATO on the Green Line, since trips would be impractical. That would cut the capacity of the central subway drasticly!

<sarcasm>
Oooh...those random pointless brake-slam dead stops will be ever so much fun in a packed side-to-side rocking Type 7 on the D line's 50 MPH stretches.
</sarcasm>

rail10 wrote:Why does the green line have no trip arms or automatic train protection system unlike the other lines?

THERE ARE A NUMBER OF REASONS ALL OF WHICH WOULD REQUIRE ME TO WRITE A BOOK. SEVERAL REASONS ARE: 1. THE DENSITY OF TRAFFIC REQUIRE THE TRAINS TO TRAVEL CLOSER TOGETHER THAN THE SAFE BRAKING DISTANCE CRITERIA FOR EITHER TRIP STOPS OR ATP. IF EITHER SYSTEM WERE TO BE USED TRAIN CAPACITY THUS PASSENGER LOAD WOULD DECREASE TO A POINT WHERE IT WOULD RENDER THE SYSTEM INOPERABLE.Outside on the riverside line either of the systems would work satisfactorily. INTOWN STATIONS REQUIRE DOUBLE BERTHING. THE EQUIPMENT TO ALLOW THIS AUTOMATICALLY WOULD BE PROHIBITIVELY COSTLY.

THERE ARE NEW TECHNOLOGIES THAT MAY ALLOW ATP SUCH AS MOVING BLOCK ETC THAT HAVE BEEN DEVLOPED BUT AS FAR AS I KNOW NOT BEEN APPLIED. WITH A NEW ATP SYSTEM A SERIOUS ALTERATION TO THE TRAIN ROUTES WOULD ALSO NEED TO BE STUDIED AND IMPLEMENTED SUCH AS WIDENING THE TUNNEL AND ADDING TRACKAGE FOR MORE TRACKS ROUTES IN THE CORE AREA. THOUGHOUT THE YEARS WHILE BILLIONS WHERE BEING SPENT INCLUDING MODERNIZING PARK STREET STATION 4 TIMES, ARLINGTON STATION 3 TIMES AND OTHER MULTIBILLION DOLLAR EXPENDITURES, MINISCULE FUNDS HAVE BEEN ALLOCATED TO ONE OF THE MOST IMPORTANT CORE SECTION OF THE GREEN LINE, CONSEQUENTLY IT WILL CONTINUE TO BE WHAT IT IS, AN IMPORTANT BUT ANTIQATED, INEFFICIENT SYSTEM OF TRANSPORTING PEOPLE. INSTEAD OF SPENDING HUNDREDS OF MILLIONS TO BUILD THE SILVER LINE WHY NOT EXPAND THE GREEN LINE DOWNTOWN TUNNEL INSTEAD?

Type in all caps = I ignore your post.

It's not 1995, you should know these things by now.

Arborway wrote:Type in all caps = I ignore your post.

It's not 1995, you should know these things by now.

That post hurts my eyes, can't ever read it!

The faster you go, the longer it takes to stop. Most places on the green line don't run all that fast. Cars at Boylston routinely start pulling into the station platform before the train ahead has completely stopped loading and left the platform. To allow this via signal, an auto-stop device would have let the train pass anyways.

IIRC, most auto-stops only work if a train runs a signal. It seems to me that most signals on the Green Line are in the underground subway portion, and that they only really show whats directly ahead of the car - be it another train, or proper alignment of a switch. Because of that, I don't really see there being a huge benefit for a train-stop device. Unless the operator became incapable of running the car (which could happen, but I don't know if it has), the only other reason for an auto-train-stop would be an operator missing a signal - which seems pretty hard to do in the subway. I don't want to say auto-stops are a bad idea, I'm just not sure that for the majority of situations on the Green Line they would be of any help.

There are actually a few things I'd like to know now :

1. How much do Green Line operators rely on line-of-sight
vs. signals in the subway?
2. What was the cause of the incident @ Boylston? Missed signal? Speeding into the station? Sudden brake application of the train ahead?
3. What, if any, recent accidents were caused by motormen loosing their ability to control the car?
4. (I should know this, but) Do green line cars have a deadman on them?

Stmtrolleyguy wrote:
1. How much do Green Line operators rely on line-of-sight
vs. signals in the subway?

An operator must wait 1 minute at a red signal and proceed at 6 mph, ready to stop short. Passing a double red under any circumstance, or failure to follow the above, can get them suspended

4. (I should know this, but) Do green line cars have a deadman on them?

They do - on the control handle of the Type 8s and via a foot pedal on the Type 7s