SAFE RAILWAY WORKING. 671 



at such station it would necessarily have passed the home signal and 

 possibly the signal box, and thus have technically broken the block 

 system were the section in advance occupied and the signal box the 

 boundary. With this arrangement, when the section ahead is 

 blocked, stopping trains are held up at the starting signal, and non- 

 stopping ones at the home signal. 



In South Australia the more important lines are worked on 

 what is there termed the '" absolute block system," and those on 

 which the traffic is light on the " permissive block.'' "' Absolute block" 

 there means something different to what is us' d elsewhere, No. 81 of 

 the South Australian liule Book reading as folloAvs : — " After the 

 ' line clear' signal has been returned in answer to the question ' is line- 

 clear T the line must not be obstructed until the train has arrived, 

 except for shunting purposes in station yards, and only then when, 

 efficientl}' protected by fixed semaphores or hand signals." At first 

 glance this would seem to imply that " line clear" in South Australia 

 is the equivalent of "section clear, but station"' or "junction blocked" 

 of Great Britain, New South Wales, and Victoria, but this has to be- 

 lead in conjunction with No. 145, the first part of which is as follows: 

 — " Every engine man shall bring his train to a standstill at the- 

 distant signal when the arm or light indicates danger. Having done 

 so, he must, without a moment's delay, move gently foiward past 

 such distant signal so far as he may see his road is clear, until close- 

 up to the home signal (except as provided for in Rule 148), and there 

 wait a signal from it or verbal permission from the signalman to- 

 pioceed." It will thus be seen that the South Australian distant 

 signal is an " absolute stop" signal, and not, as elsewhere, merely an 

 indication as to the probable position in which the driver will find a 

 signal in advance. Hence, in South Australia, before a driver could 

 cause an accident by running into a station in which shunting is 

 going on, he would have to pass two stopping signals at a consider- 

 able distance apart, complying with the conditions mentioned by the 

 writer at an earlier part of this paper. In fact, the South Australian 

 practice may be considered the equivalent of converting each station 

 into a section, separate and distinct from the approach section on 

 either side. In this respect the practice is undoubtedly safe, but this 

 may involve delay to the through traffic, which would be unadvisable 

 on busier lines. 



The block system generally adopted in Australia is that termed 

 by Langdon, in his " Applications of Electricity to Railway Work- 

 ing," the " affirmative system," by which the sig-nal man in the rear 

 has to ask his comrade in advance for permission to let the incoming 

 train enter the section, altliough he has already been advised that 

 the train previously admitted has reached the station in advance. 

 This is generally considered the safest system, but it involves the 

 noting of three separate conditions of the line, viz. : — 



(a) Section empty, but permission not granted for a train to 



enter ; 



(b) Section empty, and permission granted for a train tO' 



enter; and 



(c) Train on line. 



