Headway consists of expressing the interval between preceding and following trains under normal operating conditions in units of time. The distance spacing in this case is the interval between two trains when the following train has reached the position relative to the preceding train where blocking requires braking operation (roughly three block sections).
The headway is the time required for the train to run over this distance.
The headway is calculated for each signal in automatic block sections, then a margin (about 10 seconds) is added to the largest value and the results are used as the minimum headway for the railway division in question.
Accordingly, the minimum headway differs according to the signal positions, block section length, train length, acceleration, deceleration and other factors. However, the stopping time in stations is the most important factor, with about two minutes considered the limit for commuter train sections and three minutes for general long train (15 cars) sections.
Fig. 11 shows an example of headway around a station. The means of the symbols used in the figure are as follows.
T : Headway
t1 : Signal changing time (1 sec.)
t2 : Time after the train starts until the end of the train enters the inside of the departure signal
t3 : Stopping time
t4 : Time after the front of the train enters the inside of the home signal until the train stops
t5 : Time to run between the rear No. 1 block signal and the home signal
t6 : Time to run the distance required to decelerate from the planned speed to 45 km/h at the planned speed
t7 : Margin time after the driver confirms the signal until performing the control operation (3 sec.)
