> Railway Age June 15, 1959 talks about "Q's Modified CTC cuts Costs" This was
> the "poor man" CTC where only one switch at a siding were controlled with the
> other a spring switch.
I worked over that half-azzed CTC and between Ravenna and Alliance and it was
ok as long as only one train in each direction met at a siding. But get TWO
trains meeting one at the same siding and you immediately have problems.
For example:
Most of the sidings as I recall had the power switch at the east end and the
spring switch at the west end (a few were the opposite). Normal procedure for a
meet was that the westbound train was lined into the siding at the east end's
power switch. The eastbound train would come up the mainline next to the
siding. When the westbound was in the clear the DS would normalize the power
switch and the eastbound on the main could depart. This was just like REAL CTC.
However, unlike full CTC where the westbound could be lined out of the siding
as soon as the eastbound on the main cleared the west switch, with this
poor-man's stuff the westbound had to wait until the eastbound cleared the
control point at the EAST switch because the signal at the west-end spring
switch could not clear until then. That was because with only the single
control point at the east switch the CTC system "thought" the long single track
section to the next siding was still occupied with an opposing train, which it
was, the EB on the main. This was not much of a problem when one train met one
train. It only resulted in the WB having to wait in the siding a few minutes
longer to allow the EB to clear the east end control point so the WB could get
a siding departure signal.
But consider what happens when TWO westbounds meet an eastbound. The first WB
is lined into the siding as normal at the east power switch. The second WB
stops on the main east of the east power switch because the sidings were only
long enough for one train. The one eastbound stops on the main next to the
siding. The eastbound and 2nd westbound are staring at each other face to face
at the east switch control point. Because the eastbound is occupying the main
between switches and is west of the east switch control point, the CTC
rightfully "thinks" there is an opposing train (eastbound) between the control
point at this siding and the control point at the next siding west. Thus the
signals' current of traffic remains EASTBOUND and cannot be set to WESTBOUND to
allow the WB train to depart the siding at the west end spring switch.
Stalemate. The railroad is grid locked.
The only thing to do is for the DS to talk the WB past the red siding signal at
the spring switch, against the signal system's established current of traffic.
The westbound departs the siding running on a red signal. The 2nd WB gets the
signal at the east end CTC control point and pulls into the now vacant siding.
Now the power switch at the east end can be normalized and the signal given for
the EB on the main to depart. The EB departs and finally clears the main west
of the control point. But...
The first WB is still plodding along at Restricted speed west of the siding
running on red block signals. EVERY signal between this siding and the next
siding 15-20 miles away will be red because the signal system's established
current of traffic never got a chance to reverse for westward movement. This
makes for a VERY slow run to the next siding. The poor second WB in the siding
has two choices at this point.
1. Get talked by the red signal at the spring switch and slowly follow the
first EB all the way to the next siding, or..
2. Wait until that slow moving first WB finally gets to the next siding and
clears its control point so the signal system's circuits can finally reverse
current of traffic for westward movement. At that point in time the 2nd WB can
finally get a signal to depart the first siding!
There was another way.
The eastbound ABS signal protecting the spring switch at the west end of the
sidings had a "Take Siding" aspect that consisted of a pair of diagonally
aligned lunar lights below the main head (We called them dumbells). The DS had
control of those lunar lights and could activate them thus telling an eastbound
train to stop and hand line themselves into the siding at the spring switch.
Any westbound trains would be held east of the east switch control point until
the eastbound got into the clear in the siding and lined the spring switch back
for the main. Once this was done the CTC system "saw" that the long single
track section between this siding's east end control point and the control
point of next siding to the west was clear of all trains and it then could
reverse the current of traffic for westward movements. The westbounds stopped
east of the east power switch control point could now get a signal to depart
westward using the main between this siding's switches and they would both get
appropriate clear signals westward. Once the 2nd WB got past the east switch
control point the DS could reverse the power switch and give the EB a signal to
depart off the siding.
Basically this scenario of putting the EB into the siding via the dumbell
signals and the crew hand throwing the spring switch in effect nullified the
efficiency gains of a CTC system.
The CB&Q's cheapness of installing this half-azzed CTC came back to bite them
in the butt as traffic increased. Either way the meet was performed it created
quite a delay. As a result it was changed to full CTC in the late 1970s.
AK
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