Timetable, Train Order, Block and Block Signal

Posted by PITHOCRATES - November 20th, 2013

Technology 101

The Preferred Method of avoiding Train Collisions is not being where another Train Is

Automobiles are relatively light and nimble.  It doesn’t take much energy to get them moving.  And it doesn’t take much energy to stop them.  A person only needs a steering wheel, an accelerator pedal and a brake pedal to go safely from point A to point B.  And if someone is texting and driving and veers into your lane you can do a few things to avoid a collision.  Such as stopping quickly by stepping on the brake pedal.  Twisting the wheel quickly to move out of the way.  Or stomping down on the accelerator to pull ahead quickly.   The combination of steering, brakes and accelerator can help us avoid many collisions.  Something a train can’t do.  Because a train doesn’t have a steering wheel.  And needs about a mile to stop.

This is why we stop for trains.  And trains don’t stop for us.  Because we can stop in a much shorter distance than it takes a train to stop.  Which is why trains have the right-of-way.  And we sit at railroad crossings.  Also, without a steering wheel they can’t steer around an oncoming train.  Or around a stopped train ahead of them.  The only thing a train can do to avoid colliding with another train is to stop before hitting one.  Or not being where another train is.  The preferred method of avoiding train collisions.

So how do they keep one train from not being where another train is.  Well, they’ve used many different methods over time.  One of the earliest methods was scheduling trains by a timetable.  Say there is a section of single track connecting two cities.  At, say, 8AM one passenger train leaves point A.  While another passenger train leaves point C.  They travel towards each other on a single track.  At approximately 9AM both trains arrive at point B.  The timetable will have one train pull into a siding and wait for the other train to pass by on the main line.  After the other train clears the track between point A and point B and continues on to point C the train on the siding will return to the main line and continue to point A.  According to the timetable.

Shorter Blocks mean less Waiting Time for a Train Ahead to Exit a Block

Of course, the timetable had its faults.  Such as when two trains were traveling in the same direction.  For example, let’s say train A and train B are moving from point C to point B to point A.  Train B leaves 2 hours after train A.  Which provides a two hour separation between trains.  Allowing train A to clear the track long before train B comes through.  Unless, of course, train A breaks down.  Which would be very bad for train B coming around a bend at speed only to see the rear end of the stopped train A.  And with no steering wheel or enough distance to stop train B would run into the back of train A.  Causing great damage.  And loss of life.

The timetable also made for inefficient use of track.  For it required large time separation of trains.  Which meant fewer trains in a given period of time.  And less revenue.  To increase revenue they had to shorten the time separation of trains.  Without decreasing train safety.  And the telegraph allowed us to do that.  With faster-than-train communication we could send new instructions ahead of a train (i.e., a train order).  Such as at the next station it will reach.  Telling them to stop on a siding for a priority train to pass.  Or to proceed slowly and be prepared to stop when they reach a broken down train ahead of them.  Etc.

We separate track into blocks.  For example, the portion of track between point A and point B is one block.  The portion between point B and point C is another block.  Trains travel through a series of blocks to get to their destination.  And to maintain the separation between trains they limit one train in a block at a time.  Ideally they want two empty blocks ahead of all trains.  So they can travel at speed through one block and have an empty block ahead of them for stopping room.  Areas with little traffic will have longer blocks than areas with more traffic.  For shorter blocks mean less waiting time for a train ahead to exit a block.

A Green Light means the next two Blocks ahead are Clear

Blocks started and ended at stations.  Signal towers.  Or block signals.  The last thing a crew does before moving their train from a stop is test the train-line air brakes.  The engineer will listen to the radio until he or she hears, “Got a good set and release.”  Meaning the brakes applied and released and were safe and functioning.  “Highball from the car department.  Have a good trip.”  The authorization to proceed.  The ‘highball’ is a reference to one of the first mechanical block signals.  A ball hoisted up by a rope and pulley.  The ball had three positions.  The high position meant the track was clear and the train could proceed at full speed.  The low position meant to stop.  And the middle position meant to proceed but to be prepared to stop at the next signal.

The semaphore was a common block signal before signal lights.  A semaphore was an arm that pivoted on one end.  When it was straight up it mean the track ahead was clear.  If it was at a 45-degree angle it meant proceed but be prepared to stop at the next block signal.  If it was horizontal it meant stop.  For there was a train in the block ahead.  Operators at signal towers would report when a train left its block to the signal tower at the entrance to that block.  So that signal operator could change the signal to clear.

Today we use electric signals.  And automation.  When a train enters a block its steel wheels and axles complete an electric circuit between the rails.  Turning the signal at the entrance to this block red.  There’s a variety of signal lights.  There are two-light units with a green light over a red light.  A green light means the block ahead is clear.  And the block ahead of that is clear, too.  Providing a 2-block separation between trains.  If the light is red it means there is a train in the block ahead.  And to stop.  If there is a green light over a red light it means the block ahead is clear but the next block is not.  So proceed at normal speed into the next block but be prepared to stop at the signal at the entrance of the following block.  Another style of signal light, the searchlight, had a single color lamp and three different lens colors that changed the color of the signal.  Green meant the block ahead was empty.  Yellow meant the block ahead was empty but the next block after that wasn’t.  And red meant to stop because there was a train in the block.  Perhaps the most common signal is a 3-lamp unit with green over yellow over red.  The signaling is similar to the 2-lamp unit.  But other combinations of colors provided additional information and direction.



Tags: , , , , , , , , , , , , ,

Power Outage stranding Electric Trains show the need for Coal and Oil

Posted by PITHOCRATES - September 29th, 2013

Week in Review

There are few more costly ways to move people than by train.  Running a passenger train is incredibly expensive.  With the biggest cost in maintaining all the infrastructure before point A and point B.  Track, signals, rights-of-way and people.  Lots and lots of people.  To build this infrastructure.  To maintain this infrastructure.  With electric trains requiring the most costly infrastructure of all.  Especially high-speed trains.  These costs are so great that they are greater than their fuel costs.  Unlike the airlines.  That provide a much more cost-efficient way to move people.

Trains are slower than planes.  And they make a lot of stops.  So they appeal to a small group of users.  So few travel by train that it is impossible to charge a ticket price that can pay for this infrastructure that people can afford.  Which is why governments have to subsidize all passenger rail except for maybe two lines.  One Bullet line in Japan.  And one high-speed line in France.  Governments pay for or subsidize pretty much every other passenger train line in the world.  Which they are only more willing to do because those ‘lots and lots of people’ are union workers.  Who support their friends in government.

So governments build passenger rail lines more for political reasons than economic.  For passenger rail is bad economics.  In a highly dense city, though, they may be the only option to move so many people.  But even then the ridership can’t pay for everything.  So it requires massive subsidies.  Worse, by relying on electrified trains so much these rail lines are subject to mass outages.  Unlike diesel electric trains.  Trains that don’t need such a costly infrastructure as electric trains do.  And with a full tank of diesel they can move people even during a large-scale power outage.  Like that currently happening with Con Edison (see Stranded NYC Commuters Ask Why Metro-North’s Power Failed by Mark Chediak & Priya Anand posted 9/27/2013 on Bloomberg).

Less than a year after Consolidated Edison Inc. (ED) left 900,000 customers in the dark during Hurricane Sandy, the utility faces the wrath of stranded commuters over a power failure that has crippled trains from New York to Boston.

Con Edison, based in New York, has warned it may take weeks to restore electricity to the Metro-North Railroad’s busiest line, which serves Connecticut and parts of suburban Westchester County. An electrical fault cut power on a feeder cable while an alternate was out of service for improvements…

The latest high-profile power failure for Con Edison follows Sandy, the worst storm in the company’s history, which brought flooding that left lower Manhattan without power for days. A few months before Sandy, New York Governor Andrew Cuomo, a Democrat, stepped in to resolve an employee lockout by the company that led to protests outside the Upper East Side home of Kevin Burke, the chairman and chief executive officer…

The rail operator is running buses and diesel-powered trains to accommodate no more than a third of the New Haven route’s regular ridership…

The power failure also affected Northeast Corridor passenger-rail service, as Amtrak canceled its Acela Express trains between New York and Boston through Sept. 29.

How about that.  Dirty, filthy, stinky diesel comes to the rescue.  Refined from petroleum oil.  As much as people hate it they can’t live without it.  No matter how hard they try.

This is what you can expect when you wage a war on reliable and inexpensive coal.  Pushing our power provides to become green only raises the cost of electric power generation.  Disconnecting coal-fired power plants from the grid removes more reliable power while replacing it with less reliable power.  And forcing power companies to invest in renewable power reduces their margins.  As they have to maintain their entire electric distribution system even if everyone has a solar power at home.  Because solar power won’t turn on your lights once the sun goes down.  And windmills won’t spin on a calm days.  So while power companies have to maintain their systems as if there is no solar or wind power they can’t bill for that capacity when the people get their power from renewable sources.  So they have little choice but to cut costs.  Leading to conflict with the unions.  And making an aging infrastructure go longer without maintenance.

You can’t have it both ways.  You can’t wage a war on coal and oil without getting costlier and less reliable power.  If you want lower-cost and more reliable power than you use coal and oil.  If you want to pay more for less reliable power then you can’t bitch when the trains stop running.  And the more we move away from coal the more our train will stop running.



Tags: , , , , , , , , , , , , , , , ,

Moving Big Things in Small Spaces

Posted by PITHOCRATES - September 11th, 2013

Technology 101

Ships once used Tugs to Maneuver around in Small Spaces but Today they use Tunnel Thrusters

As technology progressed the more things we needed to make other things.  Small factories grew into large manufacturing plants.  Which consumed vast quantities of material to produce vast quantities of goods.  Requiring ever larger means of transportation.  And we have built some behemoths of transportation.

Water transport has been the preferred method for heavy transport.  Which is why most early cities were on rivers.  As time passed our cities got bigger.  Our industry got bigger.  And our ships got bigger.  Huge bulk freighters bring iron ore, coal, limestone, etc., from northern ports across the Great Lakes to docks on small rivers and harbors further south.  On the open lakes these ships can put the pedal to the metal.  Roaring across these lakes at breakneck speeds of 15 mph.  If you’ve ever seen a Great Lakes freighter at full throttle you probably noticed something.  They push a lot of water out of their way.  Something they can’t do in those small rivers and harbors.  As their wake would push the river over its banks.  So they slow down to a non-wake speed of something slower than a person walking.

Lakes are huge bodies of deep water.  But these Great Lakes freighters, or lakers, often enter narrow and shallow rivers.  Some rivers even too shallow.  So they dredge a channel in them.  So these lakers don’t bottom out.  Some lakers have to travel upriver to offload.  Then turn around.  Which isn’t easy in a shallow river when your ship is 700-1,000 feet long.  They once used tugs to push these ships around.  But today they use tunnel thrusters.  An impeller inside a tunnel through the ship at the bow and stern perpendicular to the beam and below the water line.  Which can turn a ship without the forward motion a rudder requires.  Allowing it to move as if a tug is pushing it.  Only without a tug.

Interesting thing about Trains is that they don’t have a Steering Wheel

With the introduction of the railroad cities moved away from rivers and coastlines.  But the railroads only became a part of the heavy transport system.  Cities grew up along the railroads.  Where farmers in a region brought their harvests to grain elevators.  Trains took their harvests from these elevators to ports on rivers and coastlines.  Where they could offload to ships or barges.  And it would take a large ship or a barge.  Because one long train can carry a lot of harvest.

Interesting thing about trains is that they don’t have a steering wheel.  For there is only two directions they can go.  Forward.  And backward.  If you’ve traveled passenger rail to the end of the line you may have experienced a train turning around.  The train will reduce speed to a crawl as they switch over to a perpendicular-running track.  For trains do not travel well on curves.  Because the wheels are connected to a solid axel.  So in a turn the outer wheel needs to travel faster to keep up with the inner wheel.  But can’t.  Causing the wheels to slip instead.  Causing wear and tear on the train wheels.  And track.  Which is why curved track does not last as long as straight track.  The train travels a while on this perpendicular track at a crawl until the rear end passes another switch.  It then stops.  And goes backward.  Switching back to the track it was originally on.  Only now backing up instead of traveling forward.  The train then backs into the passenger terminal.  Ready to leave from this end of the line going forward.  To the other end of the line.

Freight trains are a lot longer than passenger trains.  Some can be a mile long.  Or longer.  And rarely turn around like a freight train.  Rail cars are added to each other creating a consist in a rail yard.  A switcher (small locomotive) moves back and forth picking up cars and attaching them to the consist.  In the reverse order which they will be disconnected and left in rail yards along the way.  Once they build the consist they bring in the go-power.  Typically a lashup of 2-3 locomotives (or more if they’re the older DC models).  The lead locomotive will typically face forward.  Putting the engineer at the very front of the train.  In the old days they had roundhouses to switch the direction of these locomotives.  Today they turn them around when they need to like the passenger train turning around.  Which is much easier as they only have to turn around one locomotive in the lashup.

Planes may Fly close to 500 mph in the Air but on the Ground they move about as Fast as Someone can Walk

Airplanes are big.  In flight they’re as graceful as a bird in flight.  But it’s a different story on the ground.  Planes are big and heavy.  They have a huge wingspan.  And the pilots sit so far forward that they can’t see how close their wingtips are to other things.  Such as other airplanes.  When they leave a gate they usually have a tug push them back and get them facing forward.  At which time they start their engines.  As it would be dangerous to start them while at the gate where there are a lot of people and equipment servicing the plane.  They don’t want to suck anything—a person or a piece of equipment—into the jet engines.  And they don’t want to blow anything away moving behind the engines as the jet blast from a jet can blow a bus away.  And has.  In flight they use their ailerons to turn.  The flaps on the tips of each wing that roll a plane left or right.  Causing the plane to turn.  The rudder is used for trimming a plane.  Or, in the case of an engine failure, to correct for asymmetric thrust that wants to twist the airplane like a weathercock.  On the ground they use a little steering wheel (i.e., a tiller) outboard of the pilot (to the left of the left seat and to the right of the right seat) to turn the nose gear wheel.

Pilots can’t see a lot out of the cockpit window while on the ground.  Which is why they rely on ground crews to give them direction.  And to walk alongside the wings during the pushback.  To make sure the wings don’t hit anything.  And that no one hits the plane.  Once the tug disconnects and the plane is under its own power the flight crew takes directions from ground controllers.  Whose job is to safely move planes around the airport while they’re on the ground.  Planes may fly close to 500 mph in the air but on the ground they move about as fast as someone can walk.  For planes are very heavy.  If they get moving too fast they’re not going to be able to stop on a dime.  Which would be a problem if they’re in a line of planes moving along a taxiway to the runway.

When we use big things to move people or freight they work great where they are operating in their element.  A ship speeding across an open lake.  A train barreling along straight track.  Or a plane jetting across the open skies.  But when we rein these big things in they are out of their element.  Ships in narrow, shallow rivers.  Trains on sharply curved track.  And planes on the ground.  Where more accidents happen than when they are in their element.  Ships that run into bridges.  Trains that derail.  And planes that hit things with their wings.  Because it’s not easy moving big things in small places.



Tags: , , , , , , , , , , , , , , , , , , , ,