This diagram shows the effect upon the headway of allowing the following train to pass Signal 47 and to approach nearer the station platform before it stopped. At the present time Signal 47 is 396 feet south of Grand Central Station platform on the northbound express tracks. After the motorman gets the signal to proceed at this point and starts his train it requires 46 seconds to accelerate the train and brake it to a complete stop at the station platform, after having moved a distance of 769 feet (396 ft. plus 373 ft.), and this cycle is shown by the first row of figures and illustrated by Figure 9.

Now suppose the train is allowed to approach within 280 feet of the platform, as shown by the second row of figures, from this position the train can start at the same time that the train at the platform begins to move and in 23 seconds it will reach the end of the platform at practically the instant that the rear end of the leaving train has cleared the other end of the platform; that is, the two trains will be the length of the platform apart. This point, which is 280 feet in the rear of the platform is the nearest possible position in which the following train can be brought to rest and get the proceed signal at the time that the leaving train begins to move, and at the same time move with safety towards the platform. If the train is brought any closer to the platform this proceed signal must be delayed or the entering train will reach the platform before the leaving train has entirely cleared it.

The distance between the platform and the point at which the following train is brought to a full stop before it is allowed to approach the platform can be reduced if the proceed signal is delayed sufficiently long so that the entering train does not reach the platform before the leaving train entirely clears it.

The third row of figures shows the effects of reducing this distance to 210 feet. From this position the platform can be reached by the following train in 20 seconds, and as it requires 23 seconds for the leaving train to clear the platform it will be necessary to delay the giving of the proceed signal for 3 seconds, and the time required by the following train to run the 140 feet to the station platform plus the length of the platform, or a total distance of 583 feet, will be 43 seconds.

In a similar manner the next row of figures shows that if a train is allowed to come to a stop at a point 140 feet from the platform the time required from the starting of one train at the platform until the next train comes to a stop at the platform will be 44 seconds.

The last row of figures indicates that if the following train is brought within 70 feet of the platform that the time elapsing between the starting of the train and the stopping of the next one will be 47 seconds.

In other words, after a certain point has been reached, the nearer the following train is brought toward the platform, the greater will be the time required between the closing of the doors of one train and the opening of the doors of the next one, and these figures indicate that the economical distance at which the following train can be brought to the rear of the platform is between 210 and 280 feet.

In making this comparative study the time which is required for the motorman to act after getting the signal and also the time required by the signals themselves to operate has been eliminated, and this time is the same in all cases, and, therefore, would not affect the result.

SPEED TIME AND DISTANCE TIME CURVES.

Showing Movement of Northbound Express Train at Grand Central Station.

This figure indicates the history of two trains on the northbound tracks at Grand Central Station; one train is leaving the station and the other is entering the station. The leaving train reaches a speed of 22 miles per hour in 23 seconds, while the entering train, if it should start at the same time, can only attain a speed of 18 miles an hour in 23 seconds on account of the curve which it encounters in approaching the station platform.

The distance traveled by the rear end of a leaving train has been shown by the diagram as well as the distance traveled by the front end of the following train, and it will be seen that on account of the lower speed of the following train the distance apart of the two trains is constantly increasing.

Another curve has been added to the diagram which shows the distance which the following train would travel before coming to a stop in case it should be necessary to apply the emergency brakes and stop the train; and this curve indicates that the

following train is never in dangerous striking distance of the leaving train, even if the following train should start to move from Signal 47, as at present located, at the same time that the leaving train starts to leave the platform.

The heavy dotted line indicates the situation that would exist if the proceed signal were advanced only 17 seconds instead of 23 seconds, as suggested in the Report, and this dotted line also indicates that the factor of safety connected with this cycle of operations is much greater than is actually required.

Suggested Location of Speed Control Signals on North Bound Express Tracks-Grand

Central Station.

This diagram is similar to Figure 2 and indicates the approximate location of two auxiliary speed control signals which can be installed on the north bound express tracks at Grand Central Station without interfering with the present signal system or with the changes proposed by the Interborough officials.

One signal which will allow the train to pass providing its speed has been reduced to 15 miles per hour is located 150 feet south of signal 47 and the other signal which is to be adjusted to stop the train if its speed exceeds 25 miles per hour is located 450 feet in advance of signal 47.

Both of these signals will be in operation while a train is at the station platform ready to stop a following train if it exceeds the indicated speeds while approaching the station and they do not clear until the first train has entirely left the platform. The entering train, however, can have its specd reduced and approach the platform and come to a stop at signal 47 without any further delay than experienced with the present signal system. The two speed control signals contribute the factor of safety that is now lacking as these signals prevent a train reaching signal 47 at full speed, when there is a train at the platform.

When these signals have been installed and their reliability has been demonstrated, a further change can be made in the signals protecting the train leaving the platform

by moving the point "A" nearer the rear end of the platform and introducing a new point "B" between point "A" and signal 8-L. At the same time, signal 471⁄2 should be moved 50 feet nearer signal 47 and a new signal 4734 installed at the rear end of the platform.

The cycle of operation of these signals will be as follows:

The leaving train will pass point "A" and clear signal 47 within 5 seconds after it starts to leave, it will pass point "B" and clear signal 471⁄2 within 15 seconds after it starts to leave, and it will pass signal 8-L and clear signal 474 within 23 seconds after it starts to leave.

The entering train will leave signal 47 within 8 seconds after the leaving train has started. It cannot reach signal 471⁄2 even if it accelerates at the highest possible rate until 20 seconds after the beginning of the cycle or 5 seconds after the signal has cleared and cannot reach signal 4734 until 30 seconds have elapsed or 7 seconds after the leaving train has entirely left the platform.

A study of the diagram shown in Figure 10 in connection with this proposed arrangement of signals will show that this cycle of operations can be carried out with perfect safety, and that a 90 second headway with a 35 second wait at the platform can be maintained, as indicated by the table shown with Figure II.

There is a possibility of saving even more than the 15 seconds indicated by moving signal 47 to within 250 feet of the end of the platform. If the entering train is stopped at and started from this position, the time allowable for a platform wait can be increased from 35 seconds to 40 seconds, and still maintain the desired 90 seconds headway.

Additional time can be secured to be added to the time allowed for this actual station wait or to compensate for irregular running of the trains by increasing the rate of acceleration by increasing the rate of deceleration and by installing signals using two sets of lights instead of the present type of signals using a moving disk, and one lamp for each indication. The possible total saving due to these refinements amounts to from 5 to 10 seconds and these savings will be found to be important items when an attempt is made to maintain a 90 second headway.

The following resolution was thereupon moved and duly seconded:

In the Matter
of

ORDER (No. 343).

The application of the Interborough Rapid

Transit Company for permission to make changes in signal system.

O-343

Whereas, Application has been made by the Interborough Rapid Transit Company for permission to make certain changes in the signal system at, or near, the express stations on the express tracks in the subway, as shown on certain drawings marked "D-277" and "D-285" submitted by said Company; and