FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION [See section 10, Rule 13] HEADWAY CONTROL DEVICE AND HEADWAY CONTROL METHOD MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. DESCRIPTION Field [0001] The present invention relates to a headway control device and a headway control method for controlling train headway. Background [0002] In related art, when a train is delayed from a train schedule, traffic control of trains includes controlling the traveling time, the departure time at a station, and the like of the delayed train so as to reduce or prevent decrease in passenger transport efficiency. Patent Literature 1 teaches a technology of a traffic control device calculating delay times of a train to be controlled, a train preceding the train to be controlled, and a train following the train to be controlled on the basis of a train schedule, position information of each train, and the like, and restricting traveling of the train to be controlled such as stopping the train to be controlled from leaving a station or lowering the traveling speed of the train to be controlled to reduce or prevent decrease in passenger transport efficiency. Because a longer headway between specific trains lowers the passenger transport efficiency, the traffic control device described in Patent Literature 1 restricts traveling of the train to be controlled in view of the delay times of the preceding train and the following train. Citation List Patent Literature [0003] Patent Literature 1: Japanese Patent Application Laid-open No. 2017-043265 Summary Technical Problem [0004] The control performed by the traffic control device described in Patent Literature 1, however, can reduce or prevent decrease in the passenger transport efficiency but has a problem in that the delay from the train schedule cannot be recovered. [0005] The present invention has been made in view of the above, and an object thereof is to provide a headway control device capable of recovering a delay from a train schedule while reducing or preventing decrease in passenger transport efficiency when a train is delayed. Solution to Problem [0006] To solve the aforementioned problems and achieve the object, a headway control device according to the present invention includes a delay time receiving unit that receives identification information and a delay time of each train within a control range. The headway control device also includes a target traveling time calculating unit that identifies a train to be controlled being a train 25 to be subjected to travel control on the basis of the delay time, determines an order in which trains travel in a traveling direction by using the identification information of each of the trains, identifies a preceding train being a train traveling ahead of the train to be controlled and a following train being a train traveling behind the train to be controlled on the basis of the order, and calculates a target traveling time of the train to be controlled in a travel section in which the train to be controlled travels next by using a normal traveling time set for normal traveling in the travel section, the delay time of the train to be controlled, the delay time of the preceding train, and the delay time of the following train. The headway control device also includes 5 a target traveling time transmitting unit that transmits the target traveling time to the train to be controlled. Advantageous Effects of Invention [0007] According to the present invention, the headway control device produces an effect of recovering a delay from a train schedule while reducing or preventing decrease in passenger transport efficiency when a train is delayed. Brief Description of Drawings [0008] FIG. 1 is a diagram illustrating an example of a configuration of a traffic control system according to a first embodiment. FIG. 2 is a block diagram illustrating an example of a configuration of a headway control device according to the first embodiment. FIG. 3 is a diagram illustrating a change in the number of passengers when travel control of a train is not performed in the case where the train is delayed. FIG. 4 is a flowchart illustrating operation of the headway control device according to the first embodiment for performing travel control on a train to be controlled that is delayed. FIG. 5 is a diagram illustrating an example of a case where processing circuitry included in the headway control device according to the first embodiment is constituted by a processor and a memory. FIG. 6 is a diagram illustrating an example of a case where processing circuitry included in the headway control device according to the first embodiment is constituted by dedicated hardware. FIG. 7 is a diagram illustrating an example of a configuration of a traffic control system 5 according to a second embodiment. Description of Embodiments [0009] A headway control device and a headway control method according to certain embodiments of the present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the embodiments. [0010] First Embodiment. FIG. 1 is a diagram illustrating an example of a configuration of a traffic control system 100 according to a first embodiment of the present invention. The traffic control system 100 includes trains 14, 15, and 16, a headway control device 30, and a radio base station 40. [0011] The trains 14 to 16 each include an on-board device and an automatic train operation (ATO), which are not illustrated. The on-board device generates a run-curve indicating the relation between the position and a target speed of the subject train on which the on-board device is mounted on the basis of set traveling times between stations. The ATO controls the traveling of the subject train in accordance with the generated run-curve. The trains 14 to 16 each measures a delay time at departure from a station each time the trains 14 to 16 leave a station, and transmits identification information and the delay time to the headway control device 30. The identification information is a train number set to be used during operation of each train. Even trains having the same train car composition have different train identification information, that is, different train numbers from each other when the trains are operated in different time periods from each other. A delay time is a time difference between a departure time 5 set in a train schedule and an actual departure time at a station that each train having a train number has left. A delay time may be a time difference between a passage time set for normal operation and an actual passage time when a train has passed a specific point, such as a specific wayside coil. Even when no delay has occurred, the trains 14 to 16 each set a delay time of 0, and transmit the identification information and the delay time. In FIG. 1, the direction from left to right in the drawing will be referred to as the traveling direction of the trains 14 to 16. While only two stations 25 and 26 are illustrated in FIG. 1, one or more stations are assumed to be actually present to the left of the station 25 and to the right of the station 26. [0012] The radio base station 40 is installed on the ground, and relays communication between the trains 14 to and the headway control device 30. The communication between the radio base station 40 and the headway control device may be radio communication or cable communication. The communication between the radio base station 40 and the trains 14 to 16 is radio communication; however, other existing communication schemes such as communication using pickup coils, which are not illustrated, installed on the trains 14 to 16 and wayside coils installed on the ground, may be used. [0013] When any of the trains 14 to 16 within a control range of the headway control device 30 is delayed, the headway control device 30 performs control to restore the operation to that according to the train schedule while reducing or preventing decrease in passenger transport efficiency. In the first embodiment, the headway control device is equipment installed on the ground. The headway control device 30 may be installed in a base device or the like, which is not illustrated, or 5 may be installed as independent equipment, for example. [0014] A configuration of the headway control device 30 will be described. FIG. 2 is a block diagram illustrating an example of the configuration of the headway control device according to the first embodiment. The headway control device 30 includes a delay time receiving unit 31, a target traveling time calculating unit 32, and a target traveling time transmitting unit 33. [0015] The delay time receiving unit 31 receives identification information and a delay time of each train within the control range of the headway control device 30 from the trains within the control range via the radio base station 40. In FIG. 2, identification information is referred to as a train ID (identification). The delay time receiving unit 31 outputs the received identification information and delay times to target traveling time calculating unit 32. Note that the delay time receiving unit 31 may hold the received identification information and delay time. In this case, upon receiving the identification information and a delay time transmitted from each train at departure from a next station, the delay time receiving unit 31 updates the held delay time. In the case of holding the delay times of the respective trains, the delay time receiving unit 31 holds 0 indicating that no delay has occurred as initial values. [0016] The target traveling time calculating unit 32 determines a train to be controlled that is a train to be subjected to travel control on the basis of the delay times of the respective trains. When a delay time of a train is equal to or longer than a preset threshold, for example, the target traveling time calculating unit 32 determines that this train is delayed, and determines this train as a train to be controlled. In the example 5 of FIG. 1, the target traveling time calculating unit 32 determines the train as a train to be controlled. The target traveling time calculating unit 32 determines the order in which the trains travel in the traveling direction of these trains by using pieces of the identification information of these trains. Because the identification information, that is, the train numbers are set in advance in the train schedule, the target traveling time calculating unit 32 can recognize the preceding and following relations of the trains, that is, the order in which the trains travel in the traveling direction on the basis of the train numbers. The target traveling time calculating unit 32 identifies a preceding train, which is a train traveling ahead of the train to be controlled, and a following train, which is a train traveling behind the train to be controlled, on the basis of the determined order. In the example of FIG. 1, the target traveling time calculating unit 32 identifies the train 14 as the preceding train, and the train 16 as the following train. The target traveling time calculating unit 32 calculates a target traveling time in a travel section in which the train to be controlled travels next by using a normal traveling time set for normal traveling in the travel section, the delay time of the train to be controlled, the delay time of the preceding train, and the delay time of the following train. In other words, the target traveling time calculating unit 32 calculates the target traveling time by using the normal traveling time and the delay times of the three trains. The travel section is a section between a first stop at which the train to be controlled is stopped and a second stop at which the train to be controlled stops next. The normal traveling time is an inter-station traveling time set for normal traveling between the first stop and 5 the second stop. Details of a method for calculating the target traveling time by the target traveling time calculating unit 32 will be described later. The target traveling time calculating unit 32 outputs the calculated target traveling time together with the identification information of the train to be controlled to the target traveling time transmitting unit 33. [0017] The target traveling time transmitting unit 33 transmits the target traveling time calculated by the target traveling time calculating unit 32 to the train to be controlled via the radio base station 40 by using the identification information of the train to be controlled. The target traveling time transmitting unit 33 may transmit the target traveling time at preset intervals, or each time the target traveling time is obtained from the target traveling time calculating unit 32. Note that the target traveling time transmitting unit 33 may hold the identification information and the target traveling time obtained from the target traveling time calculating unit 32. In this case, upon obtaining a next target traveling time for the train to be controlled having the same identification information from the target traveling time calculating unit 32, the target traveling time transmitting unit 33 updates the held target traveling time. [0018] A change in passenger transport efficiency in a case where a train is delayed will now be explained. FIG. is a diagram illustrating a change in the number of passengers when travel control of a train is not performed in the case where the train is delayed. FIG. 3 illustrates an example in which only the delayed train is delayed and neither of the preceding train and the following train are not delayed. Typically, the train schedule is set so that the intervals between trains, that is, the 5 headways are not significantly different between successive headways in normal operation state based on the train schedule in which no delay has occurred. This is because a significant difference between headways causes the degrees of crowdedness significantly different among trains, which increases the time for passengers to get on and off a train with more passengers and makes the train likely to delay. In a case where only a delayed train 55 is delayed and a preceding train 54 and a following train 56 are not delayed as illustrated in FIG. 3, the headway between the preceding train 54 and the delayed train 55 becomes too long, which increases the number of passengers waiting at the station 26 as compared with that before the train delay. In the meantime, the headway between the following train 56 and the delayed train 55 becomes too short, which decreases the number of passengers waiting at the station 25 as compared with that before the train delay. Upon arriving at the station 26, the delayed train 55 needs to allow many passengers to get on, which increases the time for passengers to get on and off, further increases the delay, and the train schedule becomes further disrupted. In such a case, delaying the preceding train 54 can shorten the headway between the preceding train 54 and the delayed train 55, and thus can reduce or prevent the train schedule from becoming further disrupted. At the same time, this also delays the preceding train 54 that could operate normally, which can disrupt the train schedule of trains in a wide range. [0019] Thus, in the first embodiment, when a train within the control range is delayed, the headway control device 30 performs travel control of the delayed train so as to restore the train schedule while reducing or preventing the decrease in passenger transport 5 efficiency. [0020] In the first embodiment, the target traveling time calculating unit 32 of the headway control device 30 actually determines one or more trains traveling within the control range of the headway control device 30 as trains to be controlled, and calculates the target traveling times of the trains to be controlled. While only the trains 14 to 16 are illustrated in FIG. 1, it is assumed that a train 13, which is not illustrated, is present to the right of the train 14, and that a train 17, which is not illustrated, is present to the left of the train 16. In this case, when the train 14 is delayed, the target traveling time calculating unit 32 can determine the train 14 as a train to be controlled, the train 13 as a preceding train, and the train 15 as a following train, and calculate the target traveling time of the train to be controlled, that is, the train 14. In addition, when the train 16 is delayed, the target traveling time calculating unit 32 can determine the train 16 as a train to be controlled, the train 15 as a preceding train, and the train 17 as a following train, and calculate the target traveling time of the train to be controlled, that is, the train 16. When no preceding train is present, the target traveling time calculating unit 32 may set the delay time of the preceding train to 0. For example, no preceding train is present for an operation start train that is the first train. In addition, when no following train is present, the target traveling time calculating unit 32 may set the delay time of the following train to 0. For example, no following train is present for an operation end train that is the last train. Thus, each train can be a train to be controlled, a preceding train, and a following train. The method for calculating the target traveling time of a train to be controlled by the target traveling time calculating unit 32 5 is, however, the same for any combination of a train to be controlled, a preceding train, and a following train. Thus, an example of a case where a train to be controlled is the train 15, a preceding train is the train 14, and a following train is the train 16 as illustrated in FIG. 1 will be described below. [0021] Specific operation of the headway control device will be explained. FIG. 4 is a flowchart illustrating operations of the headway control device 30 according to the first embodiment for performing travel control on a train to be controlled that is delayed. In the headway control device 30, the delay time receiving unit 31 receives the identification information and a delay time from each of the trains 14 to 16 within the control range of the headway control device 30 via the radio base station 40 (step S11). The delay time receiving unit 31 outputs the received identification information and delay times to target traveling time calculating unit 32. [0022] The target traveling time calculating unit 32 determines whether or not a delay has occurred to the trains 14 to 16 within the control range on the basis of the identification information and the delay times obtained from the delay time receiving unit 31 (step S12). As described above, when a delay time is equal to or longer than a preset threshold, the target traveling time calculating unit 32 determines that a delay has occurred. The target traveling time calculating unit 32 permits a delay time shorter than the threshold. If it is determined that no train is delayed (step S12: No), the target traveling time calculating unit 32 terminates the processing. If it is determined that there is a train that is delayed (step S12: Yes), the target traveling time calculating unit 32 determines the train 5 determined as being delayed as a train to be controlled subjected to travel control. In the example of FIG. 1, the target traveling time calculating unit 32 determines that the train 15 is delayed, and determines the train 15 as a train to be controlled. [0023] The target traveling time calculating unit 32 determines the order in which the train travel in the traveling direction of the trains by using the identification information of each train (step S13). As illustrated in FIG. 1, the target traveling time calculating unit 32 determines that the train 14, the train , and the train 16 are traveling in this order in the traveling direction. The target traveling time calculating unit 32 identifies a preceding train traveling ahead of the train to be controlled, that is, the train 15, and a following train traveling behind the train to be controlled, that is, the train 15 on the basis of the determined order (step S14). As illustrated in FIG. 1, the target traveling time calculating unit 32 identifies the train 14 as the preceding train and the train 16 as the following train. [0024] The target traveling time calculating unit 32 calculates the target traveling time in a travel section in which the train to be controlled, that is, the train 15 travels next by using formula (1) and formula (2) (step S15). [0025] tc(i),s(j)=ttmp(ttmp≥trs(j)) =trs(j)(ttmp