Witness Testimony given by Elfric Wells Chalmers Kearney (Part 5).

 3149, I think you want to compare that with the pace that trains go somewhere abroad? ---

Yes. The question may arise as to the capacity of the tubes dealing with this, what might be thought to be, rather dense traffic. I believe that the northern tubes and the eastern and southern tubes could independently easily deal with the whole of the traffic into and out of the Clearing House.

Here we have a train interval of practically 4 1/2 minutes between one train and the next, that is to say, supposing all the trains of the east and the south and the north concentrated on these two tubes, you would have a train passing each way every 4 1/2 minutes. On the Brooklyn Bridge in New York they pass a train every 30 seconds, and it is done by very short overlapping blocks. Suppos you call those the spans of Brooklyn Bridge, you have a signal about every car length all the way across the bridge, and one train is hardly over the bridge before another one enters the bridge, I think the number is ten, I am not quite sure about the number, but there must be a certain number of red lights behind the train that is just preceding. The advantage of having these short sections is that you can have a very much nearer approach of the following train and much greater density of traffic. In fact, it would be quite impossible to work 120 trains an hour over a single track by any other means. The maximum density on the underground is supposed to be 40, though I have never actually caught it being more than 37. The question may arise as to how the eastern traffic is to be dealt with supposing some catastrophic happened on the tube and it was entirely shut down. There are two tracks running in from Liverpool Street on the Metropolitan railway; certain rails have been removed, but they could easily be replaced to provide against every possible eventuality, so that in case those tubes got shut down traffic could be brought here during the night when the ordinary passenger traffic was shutdown, brought round and enter the Clearing House from the north.