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12-9 question


KUN174

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OK then do you think it would be very simple to just pull an almost 640 ft long

Train to a stop in a second. It takes a while there is an amount of distance needed before the train can come to a complete stop. Though if someone is standing at 30 yards and it will take the train 60 yards to stop there is no way you can avoid a 12-9. Its almost like the RMS Titanic and the iceberg it was way to close to stop the ship from hitting it. The same method goes to trains if its too close you cant avoid hitting the object because it takes time before it pulls to a complete stop but by then it would be too late because you already hit the person or object.

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Here's my question, if a 12-9 is about to happen why can't the T/O slow down the train and brake instead of hitting the person then stopping?

 

You obviously must think it's sooooooooo easy for a train operator to stop a million-pound consist of metal on wheels.

 

It isn't!

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Here's my question, if a 12-9 is about to happen why can't the T/O slow down the train and brake instead of hitting the person then stopping?

 

Think about it. If it takes over 500 feet to stop a train, and the person's 100 feet away, what do you think will happen? Hancock will drop from the sky and stand in front of the train?

 

Simple answer: No.

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Wirelessly posted via (Mozilla/5.0 (Danger hiptop 4.6; U; rv:1.7.12) Gecko/20050920)

 

Here's my question, if a 12-9 is about to happen why can't the T/O slow down the train and brake instead of hitting the person then stopping?

 

The average train comes into a station at 25-30 mph, depending on the station. Most 12-9's happen when the train is like 10 feet away from the person ready to jump. Its damn near impossible to stop something that big that quickly.

Imaging driving your car and a deer jumps in front of it. Now imagine that on a much larger scale

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Physics:

A platform can be from 150 meters to 180 meters. The train enters the station at an initial velocity of 14 meter/seconds. To find the time is takes for a train to slow down from 14 m/s to a complete stop of 0 m/s, we use: time = 2 * displacement / velocity, which is equal to: time = 2 * 180 m / 14 m/s. Thus time is equal to 25.71 seconds. It takes a train around 26 seconds to come to a complete stop, from the time it enters the station to the time it stops. Clearly, a train cannot go from 14 m/s (30 mph) to 0 m/s (0 mph) in 1 second, making it impossible for the T/O from preventing a 12 - 9. The only person at fault here is the person who gets on the track.

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Physics:

A platform can be from 150 meters to 180 meters. The train enters the station at an initial velocity of 14 meter/seconds. To find the time is takes for a train to slow down from 14 m/s to a complete stop of 0 m/s, we use: time = 2 * displacement / velocity, which is equal to: time = 2 * 180 m / 14 m/s. Thus time is equal to 25.71 seconds. It takes a train around 26 seconds to come to a complete stop, from the time it enters the station to the time it stops. Clearly, a train cannot go from 14 m/s (30 mph) to 0 m/s (0 mph) in 1 second, making it impossible for the T/O from preventing a 12 - 9. The only person at fault here is the person who gets on the track.

 

No offense, but you should check your physics book. Don't post formulas unless your sure.

 

Looking at the case of an R160 traveling 30mph (=44ft/s): with an emergency braking rate of 3.2mph/s, it would take an R160 9.38 seconds to come to a complete stop, at which by that time it would've traveled 206 ft from the time of brake application. Account for a three second response time and the distance increases to 338 ft from the initial response. That's almost he entire length of an IRT platform. A train does not even need to go 5mph to cause fatal injuries.

 

This is ideal, not taking into account passenger loading and other conditions, including grades, condition of equipment, etc. Mind you, it only gets worse for older equipment.

 

Everyone else already answered the question, I just wanted to get the numbers right.

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No offense, but you should check your physics book. Don't post formulas unless your sure.

 

Looking at the case of an R160 traveling 30mph (=44ft/s): with an emergency braking rate of 3.2mph/s, it would take an R160 9.38 seconds to come to a complete stop, at which by that time it would've traveled 206 ft from the time of brake application. Account for a three second response time and the distance increases to 338 ft from the initial response. That's almost he entire length of an IRT platform. A train does not even need to go 5mph to cause fatal injuries.

 

This is ideal, not taking into account passenger loading and other conditions, including grades, condition of equipment, etc. Mind you, it only gets worse for older equipment.

 

Everyone else already answered the question, I just wanted to get the numbers right.

 

Side note: Passenger loading is irrelevant. New techs have deceleration rates controlled accordingly by electronics, and ideally everything in the braking system (air, since we're talking about an emergency stop*) adjusts to achieve the desired rate. Older subway cars contain variable load valves which automatically adjust the braking effort to compensate for the weight (or lack of weight) of the passengers on board the car.

 

* Dynamic brakes are irrelevant during emergency stops. 100% of the brake application is provided by the car's air brakes.

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Dynamic brakes are irrelevant during emergency stops. 100% of the brake application is provided by the car's air brakes.

 

"When emergency braking is applied no dynamic braking is in effect only friction"

 

Good stuff Subway Guy :tup:

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Here's my question, if a 12-9 is about to happen why can't the T/O slow down the train and brake instead of hitting the person then stopping?

 

The emergency brake is to be applied only when an emergency exists. A person in front of a train in danger of being hit certainly is considered an emergency.

 

But for hypothetical sake, let's just say that I'm the T/O on the imaginary (X) train. I see someone on the tracks a couple hundred feet away. I try to stop the train by using dynamic braking instead of the emergency brake.

 

BAM!

 

From this moment on, my behind will be skewered to a charcoal black by the trial lawyers looking to sue for millions.

 

That's ok, I'd rather follow the rules.

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The emergency brake is to be applied only when an emergency exists. A person in front of a train in danger of being hit certainly is considered an emergency.

 

But for hypothetical sake, let's just say that I'm the T/O on the imaginary (X) train. I see someone on the tracks a couple hundred feet away. I try to stop the train by using dynamic braking instead of the emergency brake.

 

BAM!

 

From this moment on, my behind will be skewered to a charcoal black by the trial lawyers looking to sue for millions.

 

That's ok, I'd rather follow the rules.

 

Charcoal black ? You'd be lucky to have any flesh left back there when the ambulance chasers get finished with you, LOL.

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Side note: Passenger loading is irrelevant. New techs have deceleration rates controlled accordingly by electronics, and ideally everything in the braking system (air, since we're talking about an emergency stop*) adjusts to achieve the desired rate. Older subway cars contain variable load valves which automatically adjust the braking effort to compensate for the weight (or lack of weight) of the passengers on board the car.

 

* Dynamic brakes are irrelevant during emergency stops. 100% of the brake application is provided by the car's air brakes.

 

I stand corrected. Thank you.

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Okay not real but nothing like a fantasy to help. Lets say an R160 Manhattan bound (Q) train is running from Avenue H to Newkirk Avenue. An obese and heavily drunk adult is stumbling too close to the edge falls off and blacks out. Now the (Q) is coming into Newkirk at 30 mph. The T/O sees the drunk obese man on the tracks screams and hits the brakes. From the time the T/O reacts to the drunk obese man on the track and the time it takes the train to make a complete stop the T/O realized that he ran the entire Newkirk Av platform. The T/O realizes it's too late. He either hit the obese drunk guy and killed him or injured him or if luck didn't kill him at all but he will get in trouble for it. Lets say it injured the poor guy. The Manhattan bound (Q) broke and cut the poor guy's leg. The guy goes to the hospital. Doesn't require amputation but wears a cast and the MTA will have to let the poor T/O go. Its a 12-9 and the news and everything talks about it for the week then forgets about it. Though the reason why he couldn't stop the (Q) on time is it takes time to stop the train he didn't get it. It took time to stop the moving object brakes don't stop it in a flash. Also in this scenario the guy shouldn't have been drunk on the first place :mad:. It takes a stupid person to cause a big mess.

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No offense, but you should check your physics book. Don't post formulas unless your sure.

 

Looking at the case of an R160 traveling 30mph (=44ft/s): with an emergency braking rate of 3.2mph/s, it would take an R160 9.38 seconds to come to a complete stop, at which by that time it would've traveled 206 ft from the time of brake application. Account for a three second response time and the distance increases to 338 ft from the initial response. That's almost he entire length of an IRT platform. A train does not even need to go 5mph to cause fatal injuries.

 

This is ideal, not taking into account passenger loading and other conditions, including grades, condition of equipment, etc. Mind you, it only gets worse for older equipment.

 

Everyone else already answered the question, I just wanted to get the numbers right.

 

No offense taken. :)

I just haven't taken physics in about 3 weeks, so my mind isn't fresh. BTW, I didn't know about the emergency brake rate.

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BTW, I didn't know about the emergency brake rate.

 

For an R143, the deceleration rate is 3.2 MPH/sec when you put it in the whole. I would think it's about the same for an R160.

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Okay not real but nothing like a fantasy to help. Lets say an R160 Manhattan bound (Q) train is running from Avenue H to Newkirk Avenue. An obese and heavily drunk adult is stumbling too close to the edge falls off and blacks out. Now the (Q) is coming into Newkirk at 30 mph. The T/O sees the drunk obese man on the tracks screams and hits the brakes. From the time the T/O reacts to the drunk obese man on the track and the time it takes the train to make a complete stop the T/O realized that he ran the entire Newkirk Av platform.

 

If he was coming in at 30mph and ran the entire platform while braking the train, there is something wrong with the train, since he was intending to stop there without the drunk in the way.

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