Heavy rail line of sight working

 
  Myrtone Chief Commissioner

Location: North Carlton, Melbourne, Victoria
How fast can a railcar go before its braking distance is longer than line of sight? That is on a long, straight stretch of track. Yet even at lower speeds, only one can occupy each block section or are there a few cases of heavy rail drive on sight.

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  justapassenger Minister for Railways

The absolute distance at which a train driver with their eyeline 2.5m above the rail could see to the horizon on a flat and straight track is 5.6km. The distance at which they would be able to reliably recognise an obstruction and respond would be far less than that, given that railways don't generally have a strong track record of recruiting fighter pilots or F1 drivers. I'm sure that there has been research done on this.

Heavy rail driving on sight is permitted in selected circumstances, usually only after stopping at a signal and being given authority to proceed at low speed by a secondary signal aspect or by a network controller. Terms for this sort of procedure vary according to the network on which they occur and the specific circumstance in which they occur, but include names such as 'permissive working', 'calling on aspect', 'proceed restricted authority', 'shunt signal', 'low speed aspect' etc.

The rule on the ARTC network is that the driver given 'proceed restricted authority' may proceed at a speed which enables them to stop within half of the visible sighting distance ahead, and no faster than 25 km/h.  

The reports about the Mile End and Yass Junction collisions will show you some of the issues involved with this form of working.
  Myrtone Chief Commissioner

Location: North Carlton, Melbourne, Victoria
The reports about the Mile End and Yass Junction collisions will show you some of the issues involved with this form of working.
justapassenger
But don't these reports involve locomotives hauling dead weights of carriages? I was asking about railcars because they smaller and most certainly lighter than other heavy rail stock.
  YM-Mundrabilla Minister for Railways

Location: Mundrabilla but I'd rather be in Narvik
Same Rules and principles regardless.
Ability to stop well short of any obstruction.
  justapassenger Minister for Railways

The reports about the Mile End and Yass Junction collisions will show you some of the issues involved with this form of working.
But don't these reports involve locomotives hauling dead weights of carriages? I was asking about railcars because they smaller and most certainly lighter than other heavy rail stock.
Myrtone
As said already by YMM, the same safety issues apply.

Have you read and understood the reports yet? The incidents were caused by human factors, not the vehicles involved.

There was also a major incident in Australia involving an EMU that I could have linked to but opted not to (and continue to maintain that choice) out of respect for the victims. It would be required reading for professionals in the field, but not for you.
  route14 Chief Commissioner

All cars in a train have braking force so the difference in braking capabilities between locomotive hauled trains and railcars or multiplet units isn't as much as you might imagine.
    The emergency braking deceleration of EMUs is generally at or less than 1.0 metre per second squared (That of VLocity is 1.12 metres per second squared).  Trams, another form of rail vehicle that operate under sight operation in most systems, have emergency brake of about 3.0 metres per second squared.
  justapassenger Minister for Railways

All cars in a train have braking force so the difference in braking capabilities between locomotive hauled trains and railcars or multiplet units isn't as much as you might imagine.
route14
Most of the difference is in the time it takes for an air brake application to spread down the train from the leading loco.

The majority of the difference can be closed by switching to ECP brakes, where the braking application is instantly commanded by data cabling (as in a multiple unit) instead of waiting for air pressure changes to spread.
  Myrtone Chief Commissioner

Location: North Carlton, Melbourne, Victoria
As said already by YMM, the same safety issues apply.
justapassenger
Here's some food for thought, drivers of larger and heavier road vehicles are subject to higher expectations that drivers of smaller and lighter road vehicles. But apparently the driver of a railcar (or even a hi-rail vehicle driven on rail) appears to be subject to the same expectations and drivers of longer and heavier trains sharing the same tracks.

Have you read and understood the reports yet? The incidents were caused by human factors, not the vehicles involved.
justapassenger
They are quite long reports, it would take a lot of time and patience to read through them.

All cars in a train have braking force so the difference in braking capabilities between locomotive hauled trains and railcars or multiplet units isn't as much as you might imagine.
route14
I've heard of locomotive-hauled trains taking over a mile to come to a stop. Also, I believe there was a time, back when all trains were steam-hauled, when not all train carriages had brakes, this was the time when block signalling was introduced.

The emergency braking deceleration of EMUs is generally at or less than 1.0 metre per second squared (That of VLocity is 1.12 metres per second squared).  Trams, another form of rail vehicle that operate under sight operation in most systems, have emergency brake of about 3.0 metres per second squared.
route14
Is that greater than that of the trains that ran at the time block signalling was introduced, back in the 19the century? My understanding is that trams operate under sight because they shared the road with manually steered vehicles.
A lot of newer light rail systems around the world do use block signalling on reserved track, these systems are simpler than heavy rail block signalling and may be cheaper too. Even ones to don't have signals at junctions, including crossovers.
Trams and light rail vehicles have track brakes, strangely absent from much heavier trains.

Speaking of road vehicles, even road trains appear to be driven on sight, which can be tempting to attribute to the ability to swerve. If a road vehicle stops or slows down, others behind it in the same lane can often change lanes instead of stopping or reducing speed to avoid the vehicle in front. Rail vehicles can only change tracks at crossovers, elsewhere a rail vehicle has to stop to avoid a stationary train ahead and reduce speed or stop if a rail vehicle ahead is going slower.
  route14 Chief Commissioner

I don't quite see your point.  It takes over 10 km to stop a train from 350 km/h with track-worthy brakes.  Still nothing to do with whether it's a loco-hauled train or otherwise.  Modern or modernized trams have track brakes because they have to deal with emergencies during sight operation while achieving reasonable average speed.  Trains GENERALLY have no track brakes (Some trains in Adelaide do) because they operate under signalled environment as designated.  That's the same reason why they are not meant to be operated by sight, and if they have to, the driver must take extra caution ensuring the stopping distance is well shorter than visibility AND the speed must not exceed 25 km/h, i.e. the driver must not DECIDE to increase the speed of sight operation regardless of greater visibility.
  Myrtone Chief Commissioner

Location: North Carlton, Melbourne, Victoria
I know trains generally operate under a signalled environment but I don't understand why track brakes are absent from trains. Without them, trains often can't stop within line of sight and track brakes could bring the stopping distance down to light of sight. Track brakes say on a railcar could be useful in cases where they need to be driven on sight. They can also be useful if there is a loss of traction.
  route14 Chief Commissioner

They are driven on sight with restrictive conditions.
  YM-Mundrabilla Minister for Railways

Location: Mundrabilla but I'd rather be in Narvik
I know trains generally operate under a signalled environment but I don't understand why track brakes are absent from trains. Without them, trains often can't stop within line of sight and track brakes could bring the stopping distance down to light of sight. Track brakes say on a railcar could be useful in cases where they need to be driven on sight. They can also be useful if there is a loss of traction.
Myrtone
Simple. There is no need for track brakes on rail rolling stock.
The Rules say that in the circumstances being discussed in this thread (calling on, tripped past signal, fog etc) that you do not proceed at a greater rate of knots than will allow you to stop short of any obstruction. Track brakes on trams are dangerous - better to bend someone's mudguard than break arms and legs of (often elderly) passengers in the tram.

Yet another solution looking for a problem.
  justapassenger Minister for Railways

As said already by YMM, the same safety issues apply.
Here's some food for thought, drivers of larger and heavier road vehicles are subject to higher expectations that drivers of smaller and lighter road vehicles. But apparently the driver of a railcar (or even a hi-rail vehicle driven on rail) appears to be subject to the same expectations and drivers of longer and heavier trains sharing the same tracks.
Myrtone
Correct. It has long been the practice of rail networks to hold all their drivers to professional standards instead of just some of them.

Requiring professional standards from only some of the drivers on the network works badly on the roads, and I don't think anyone in rail would want to adopt that practice.

They are quite long reports, it would take a lot of time and patience to read through them.
Myrtone
The socially correct response when someone provides you with resources to help you become more informed about an area of interest to you is to thank them.
  theanimal Chief Commissioner

They are quite long reports, it would take a lot of time and patience to read through them.
Well, patience is a skill we all need to develop, take the time to read and understand what is offered.




I've heard of locomotive-hauled trains taking over a mile to come to a stop. Also, I believe there was a time, back when all trains were steam-hauled, when not all train carriages had brakes, this was the time when block signalling was introduced.

not right, in NSW until 2002 there was the provision for time interval working, a fast train could enter a section and a slow train follow after applying a time interval. So no, block signalling was not universal.

Myrtone

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