Block Size over the years?

[CrazyDiamond]

QUOTE: Originally posted by JCSigMtr

Longer blocks equate into less signals and lower maintenance costs and I believe for that reason, most railroads today are lengthening blocks and not making them shorter.

Is this the only reason? Or is it the need for longer/heavier trains, and now that better signaling technology exists, this actually allows them to have longer blocks.....and the lower costs associated with signaling is a bonus. [?]

I think the day will come where all way side signals will be replaced with in-cab signals, the block size will shrink dramitically, and powerful computing software will bundle these 'mini-blocks' into a moving block whose size will automatically adjust depending on train parameters, i.e speed, weight, etc. For example, Instead of a physical block being 2KM long, it will only be 500 meters and the virtual moving block could be 500 to 3KM long.

[Hugh Jampton]

QUOTE: Originally posted by rrandb

I was just curious if their approach speed limits were as slow as Freight systems. It seems Commuter trains can stop quicker than a 2 mile freight? [?]

According to my info they don't have specific speeds as such. For example all it says for an advanced approach (referred to as a medium) is "Proceed. Next signal displays at least a caution or caution turnout indication."
A different document says that in areas where signal spacings are shorter for passenger trains, freight trains are restricted to 80km/h (50mph).

[jeffhergert]

Our flashing yellow is Advance Approach. Proceed prepared to stop at second signal and pass the next signal not exceeding 40mph. A yellow is Approach. Proceed reducing speed to 30mph or less, prepared to stop at next signal.
In addition to slowing trains for a possible stop, the advance approach is also used in places to slow trains for crossover moves. Many of our 40mph crossovers will have two consecutive Advance Approaches preceding the crossover.
Jeff

[rrandb]

I was just curious if their approach speed limits were as slow as Freight systems. It seems Commuter trains can stop quicker than a 2 mile freight? [?]

[Hugh Jampton]

Sorry, my info on Aussie signalling is from New South Wales (which uses flashing yellow as an advanced approach), Brisbane is in Queensland, which uses flashing yellow as an approach from the sounds of it.

[rrandb]

Yes I know that is the case in NA. He asked about "down under" but I am not familar with there system Which is Green, Yellow, Flashing Yellow and then Red.

[Hugh Jampton]

QUOTE: Originally posted by rrandb

QUOTE: Originally posted by Kozzie

QUOTE: Originally posted by jeffhergert

Where I work, when the signal system has been updated, generally the new blocks are shorter than the ones they replaced. The change has been allowed because the older signal systems went from a green (clear), to a yellow (approach), to a red (stop or stop & proceed). The new spacing includes a flashing yellow (advance approach) between the clear and the approach.
Most of the new blocks seem to be about 1.25 miles long. There are places where they are longer, a very few that are shorter. Still, most new blocks are shorter than what they replaced.
Even with this shorter individual block, you still have 2.5 miles from the first indication that you may encounter a red signal until you actually reach it.
Jeff

Jeff - I'd like to ask a related question about the flashing yellow you mentioned. [:I] Could you explain the difference between a yellow (approach), and the flashing yellow (advance approach) ? [:I]
I ask because "downunder" here on the Brisbane city suburban network (the traffic here are six car EMU's) flashing yellow is used between yellow (approach with reduced speed) and a red (stop) so it's used a little diferently down here.
Thanks for your help with this one...[;)] [:)]
Dave

Can we assume that flashing yellow indicates your next signal will be red? And that you had better be prepared to stop. Note that a yellow on a three signal system means the same thing. On your commuter system what speed does a yellow allow?

No, a flashing yellow indicates that the next signal will be a non-flashing yellow, which indicates that the next signal is red..

[rrandb]

QUOTE: Originally posted by Kozzie

QUOTE: Originally posted by jeffhergert

Where I work, when the signal system has been updated, generally the new blocks are shorter than the ones they replaced. The change has been allowed because the older signal systems went from a green (clear), to a yellow (approach), to a red (stop or stop & proceed). The new spacing includes a flashing yellow (advance approach) between the clear and the approach.
Most of the new blocks seem to be about 1.25 miles long. There are places where they are longer, a very few that are shorter. Still, most new blocks are shorter than what they replaced.
Even with this shorter individual block, you still have 2.5 miles from the first indication that you may encounter a red signal until you actually reach it.
Jeff

Jeff - I'd like to ask a related question about the flashing yellow you mentioned. [:I] Could you explain the difference between a yellow (approach), and the flashing yellow (advance approach) ? [:I]
I ask because "downunder" here on the Brisbane city suburban network (the traffic here are six car EMU's) flashing yellow is used between yellow (approach with reduced speed) and a red (stop) so it's used a little diferently down here.
Thanks for your help with this one...[;)] [:)]
Dave

Can we assume that flashing yellow indicates your next signal will be red? And that you had better be prepared to stop. Note that a yellow on a three signal system means the same thing. On your commuter system what speed does a yellow allow?

[Hugh Jampton]

QUOTE: Originally posted by Kozzie

QUOTE: Originally posted by jeffhergert

Where I work, when the signal system has been updated, generally the new blocks are shorter than the ones they replaced. The change has been allowed because the older signal systems went from a green (clear), to a yellow (approach), to a red (stop or stop & proceed). The new spacing includes a flashing yellow (advance approach) between the clear and the approach.
Most of the new blocks seem to be about 1.25 miles long. There are places where they are longer, a very few that are shorter. Still, most new blocks are shorter than what they replaced.
Even with this shorter individual block, you still have 2.5 miles from the first indication that you may encounter a red signal until you actually reach it.
Jeff

Jeff - I'd like to ask a related question about the flashing yellow you mentioned. [:I] Could you explain the difference between a yellow (approach), and the flashing yellow (advance approach) ? [:I]

I ask because "downunder" here on the Brisbane city suburban network (the traffic here are six car EMU's) flashing yellow is used between yellow (approach with reduced speed) and a red (stop) so it's used a little diferently down here.

Thanks for your help with this one...[;)] [:)]

Dave

The reason for adding flashing yellows is to increase the number of trains that a specific piece of track can handle.

On a railroad with just 3 signal indications the closest that a following train can be and the engineer still see greens when they get to the sighting point (the place where the engineer can see the signal clearly) is 2 braking distances (if they see a yellow they will apply the brakes in preparation for stopping at the next signal). This of course assumes the the signalling has been optimised so that the block lengths equal the braking performance of the train with the worst brakes on the slippryest of track.

If another indication is used (a flashing yellow) the closest that a following train can now be and the engineer only seeing greens comes down to 1 and a half braking distances. So you gain a half a braking distance between trains.
I think a drawing will show it better.


Of course this means that the cost of the signalling system doubles, but if you need the capacity it may be worth the added expense.

[Kozzie]

QUOTE: Originally posted by jeffhergert

Where I work, when the signal system has been updated, generally the new blocks are shorter than the ones they replaced. The change has been allowed because the older signal systems went from a green (clear), to a yellow (approach), to a red (stop or stop & proceed). The new spacing includes a flashing yellow (advance approach) between the clear and the approach.
Most of the new blocks seem to be about 1.25 miles long. There are places where they are longer, a very few that are shorter. Still, most new blocks are shorter than what they replaced.
Even with this shorter individual block, you still have 2.5 miles from the first indication that you may encounter a red signal until you actually reach it.
Jeff

Jeff - I'd like to ask a related question about the flashing yellow you mentioned. [:I] Could you explain the difference between a yellow (approach), and the flashing yellow (advance approach) ? [:I]

I ask because "downunder" here on the Brisbane city suburban network (the traffic here are six car EMU's) flashing yellow is used between yellow (approach with reduced speed) and a red (stop) so it's used a little diferently down here.

Thanks for your help with this one...[;)] [:)]

Dave

[Hugh Jampton]

QUOTE: Originally posted by BaltACD

QUOTE: Originally posted by jeffhergert

Where I work, when the signal system has been updated, generally the new blocks are shorter than the ones they replaced. The change has been allowed because the older signal systems went from a green (clear), to a yellow (approach), to a red (stop or stop & proceed). The new spacing includes a flashing yellow (advance approach) between the clear and the approach.
Most of the new blocks seem to be about 1.25 miles long. There are places where they are longer, a very few that are shorter. Still, most new blocks are shorter than what they replaced.
Even with this shorter individual block, you still have 2.5 miles from the first indication that you may encounter a red signal until you actually reach it.
Jeff

I must presume that very little Main Line freight traffic operates on this territory....by Main Line I am meaning freight trains of 9000 feet and longer. Mile and a quarter blocks and the the braking distances for 9000 foot 20,000 tons trains are not compatable.

No, but 2 and a half miles is plenty. It's the flashing yellow that makes all the difference. Although, even a mile and a quarter might be enough,, depends on the train speed.

[BaltACD]

QUOTE: Originally posted by jeffhergert

Where I work, when the signal system has been updated, generally the new blocks are shorter than the ones they replaced. The change has been allowed because the older signal systems went from a green (clear), to a yellow (approach), to a red (stop or stop & proceed). The new spacing includes a flashing yellow (advance approach) between the clear and the approach.
Most of the new blocks seem to be about 1.25 miles long. There are places where they are longer, a very few that are shorter. Still, most new blocks are shorter than what they replaced.
Even with this shorter individual block, you still have 2.5 miles from the first indication that you may encounter a red signal until you actually reach it.
Jeff

I must presume that very little Main Line freight traffic operates on this territory....by Main Line I am meaning freight trains of 9000 feet and longer. Mile and a quarter blocks and the the braking distances for 9000 foot 20,000 tons trains are not compatable.

[amtrakjackson]

Here in Michigan and Ohio, most blocks are about two miles long.

The Amtrak Michigan Line has a few four mile long blocks- signal 199 to signal 195, and CP160 to signal 156, for example. It also has shorter blocks- CP200 to 199, for example. But between control points, many are three miles.

[jeffhergert]

QUOTE: Originally posted by JSGreen

So, can we assume jeffhergert lives in the North East somewhere? I havent measured it, but out west here you can travel for far longer than 1.25 miles without seeing a signal head...

Drive US 30 in western Iowa.

As I said, these are new signal installations. In this case where bi-directional CTC with wayside signals were added to formerly directional, Automatic Train Control (no wayside signals) territory. Again there are longer blocks. Some are shorter. I know of one block that is only about one mile long. Some are close to where the former ATC block boundries were and some aren't. Even the longer new signal blocks in many cases are shorter than the ATC blocks they replaced.

UP and CNW signalling that has not been recently updated around Omaha/Mo Valley/Fremont still have some long blocks. Some of these probably always will be longer because of grade conditions.

Jeff

.

[beaulieu]

QUOTE: Originally posted by JimValle

I'm wondering if block sizes back in the days of timetable and train order operation weren't conditioned to some extent by the practice of running scheduled trains in several sections, sometimes as many as eight or ten at a time. Following sections ran five or ten minutes apart which probably kept them one block behind the leading section or a couple of miles back. The engineers of the following sections ran through a succession of "approach" indications trusting the leading sections to maintain a set speed so spacing remained constant. They flew green flags or displayed green markers and gave a special whistle signal to alert opposing trtaffic that other sections were following. It must have taken a lot of nerve to run like this, especially in single track territory. Doesn't this imply blocks more-or-less five miles long?

And a lot of stupidity too. This was a contributing factor to the British Southall accident of a few years ago. The driver of a Paddington bound HST was running under a series of double yellow blocks. While approaching Southall near the end of his trip, he bent over to put his stuff back into his grip, while doing so he cancelled two AWS warnings for adverse signals, assuming that they were double yellows, when in fact they were a single yellow followed by a red. Whereupon his train sideswiped a freight train crossing over into Southall Yard.
This resulted in serious personal inuries and the deaths of several passengers.
AWS only provides an audible warning of clear or adverse signals, the tone is the same for double yellow, yellow, or red. The driver must responsed by moving a lever to cancel the warning or the brakes will apply. The train was equipped with an ATP system that would have prevented the accident, but the system was prone to fail as it had done earlier in the trip and so it was shut off. Most trains running over these tracks lacked the ATP system.

[Anonymous]

In my [almost] 25 years of service as a Signalman/Signal Maintainer for the N&W and NS, I can readily attest that block lengths on the former Wabash main through west central Indiana / east central Illinois have increased from the Wabash days. The advent of ElectroCode and other types of electronic signalling have allowed block lengths to increase and in some places, we have blocks that are almost three miles in length. Longer blocks equate into less signals and lower maintenance costs and I believe for that reason, most railroads today are lengthening blocks and not making them shorter.

[PBenham]

Blocks had their length determined by lots of factors, including the number of open order stations along a particular route. If there were a lot of them, like about five miles apart, then the blocks were 2.5 miles long. The technological changes since 1920 have lengthened blocks. Radio communication and now cell phones replaced open order stations and most phone boxes. (which are vulnerable to vandalism,failure due to weather and so on) Lots of signalled lines have been renewed along the former New York Central main, with the old NYC small targets being replaced by single color tri-light signals, which then led to the end of most signal bridges. If one can do it without getting hassled get pictures of the signal bridges along the old water level east out of Buffalo, since CSX says they will be upgrading the signals here soon. I will believe it when I see it! Conrail was supposed to get $ from the feds to upgrade signals for higher passenger train speeds. CSX[:(!] does not care about Amtrak running faster. They want Amtrak to go away![:(!]

[JimValle]

I'm wondering if block sizes back in the days of timetable and train order operation weren't conditioned to some extent by the practice of running scheduled trains in several sections, sometimes as many as eight or ten at a time. Following sections ran five or ten minutes apart which probably kept them one block behind the leading section or a couple of miles back. The engineers of the following sections ran through a succession of "approach" indications trusting the leading sections to maintain a set speed so spacing remained constant. They flew green flags or displayed green markers and gave a special whistle signal to alert opposing trtaffic that other sections were following. It must have taken a lot of nerve to run like this, especially in single track territory. Doesn't this imply blocks more-or-less five miles long?

[chad thomas]

Yea, out west 2-3 miles is the normal spaceing. That's probably because our speed limits are 60-75 miles an hour.

[JSGreen]

So, can we assume jeffhergert lives in the North East somewhere? I havent measured it, but out west here you can travel for far longer than 1.25 miles without seeing a signal head...

[jeffhergert]

Where I work, when the signal system has been updated, generally the new blocks are shorter than the ones they replaced. The change has been allowed because the older signal systems went from a green (clear), to a yellow (approach), to a red (stop or stop & proceed). The new spacing includes a flashing yellow (advance approach) between the clear and the approach.
Most of the new blocks seem to be about 1.25 miles long. There are places where they are longer, a very few that are shorter. Still, most new blocks are shorter than what they replaced.
Even with this shorter individual block, you still have 2.5 miles from the first indication that you may encounter a red signal until you actually reach it.
Jeff

[Anonymous]

SPBED is correct, block size, if it has changed from the original installation, has generally increased in length due to longer braking distances (due to heavier trains) and because the need to accommodate fast passenger trains has vanished from many lines. You didn't want a passenger train to have to take a speed reduction until the last possible moment. Length of trains hasn't been a big factor -- railroads ran some very long trains back in the day, but they were typically very light.

Blocks were not originally oversized, typically, to reduce the cost of intermediate signals. That wasn't a major consideration. The cost consideration today is to get rid of intermediates, if possible, to reduce maintenance costs. The reduction in signal maintainers from 1920 today is on the order of 20 to 1, or better.

A good university or big city engineering library carries volumes of Railway Signal Engineer (it changed its name a few times), which began publication around 1910 and lasted until the 1970s or so, as well as studies on track capacity done back in the 1920s and 1930s when this science matured.

S. Hadid

[spbed]

I would surmise that cause trains are much longer then years ago siding have been lengthened to accept them & blocks have also been made longer by probably moving signals farther apart. [:D]

QUOTE: Originally posted by CrazyDiamond

When 'modern' block signaling was installed back in the day block sizing was a critical engineering both for safety and for cost control. Correct me if I am wrong, but blocks were oversized to reduce the number of signals and assosciated equipment.

Flash forward to 2006 and we are running very different trains then back then. ...basically longer heavier trains, and I think speed as remained relativily the same.

So my question is: How has block sizing varied over the years? Has it gotten longer? Or has the longer heavier trains filled these nicely such that the blocks are no longer oversized? Have the blocks shrunk some, to help maximize track capacity?

Thanks in advance. [:)]

[CrazyDiamond]

When 'modern' block signaling was installed back in the day block sizing was a critical engineering both for safety and for cost control. Correct me if I am wrong, but blocks were oversized to reduce the number of signals and assosciated equipment.

Flash forward to 2006 and we are running very different trains then back then. ...basically longer heavier trains, and I think speed as remained relativily the same.

So my question is: How has block sizing varied over the years? Has it gotten longer? Or has the longer heavier trains filled these nicely such that the blocks are no longer oversized? Have the blocks shrunk some, to help maximize track capacity?

Thanks in advance. [:)]