Quote:
Originally Posted by paulmartin
I would like to understand WHY are trains kept apart from each other and HOW is this achieved SAFELY? Anyone got any ideas?
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What's up, got an essay to write ?
(Only kidding)
1. Why
The fundamental requirement for operating a railway is that you
do keep trains apart - otherwise you risk a collision.
2. How
At the begining of the railways nobody really bothered about this as there weren't many trains around. Eventually, after a multitude of accidents and various systems being tried we arrived at the Block System whereby only 1 train is allowed in a Block at any time (there is an exception to this called Permissive Working - otherwise you could never couple trains together).
If you want to go a little deeper, there are a few variations of block. The oldest "Absolute Block" system still exists, where you have signal boxes operating semaphore signals and communicating with each other by bell codes. Mostly though there is "Track Circuit Block", where trains are detected by electrical track circuits, and this enables large Signalling Centres to control many miles of track. Additional systems exist for working over single lines, and when there is a an infrastructure failure or engineering disruption.
Fundamentally you could say the safe movement of trains relies on;
a) A signalling system which is engineered to Fail-Safe (ie, any technical failure causes a signal to revert to danger). Addtionally the Automatic Warning System helps Train Drivers to observe and comply with hazards, whilst any train which has passed a signal at danger (without authority) should be stopped before the collision point by the Train Protection and Warning System - although a considerable number of signals are not TPWS fitted.
b) Safety Critical personnel (eg, Signallers, Train Drivers, etc) having a full knowledge and understanding of the Rules, Local Instructions & Company Policies which relate to them.
I'm sure people here can add much to this, but it's a start.