Vehicle speed control device and vehicle speed control method

A vehicle speed control device that controls a speed of a vehicle when the vehicle makes a lane change from a first lane, on which the vehicle is traveling, to a second lane, in a case where the first lane merges into the second lane to disappear in front of the vehicle, or in a case where the first lane separates from a second lane in front of the vehicle, the vehicle speed control device comprising:

• a processor coupled to a memory storing instructions to permit the processor to function as:
• a first arrival time calculating unit configured to calculate a first arrival time, which is a period of time until the vehicle reaches a lane change position that is a position where a merge of the first lane and the second lane is completed or a position where a separation of the first lane and the second lane begins;
• a second arrival time calculating unit configured to calculate a second arrival time, which is a period of time until another vehicle traveling on the second lane within a prescribed range of the vehicle reaches the lane change position;
• and
• a speed control unit configured to control the vehicle according to the first arrival time, the second arrival time, and a weight of a load that the vehicle is loaded with,
• wherein, in a case where the first arrival time is equal to or greater than the second arrival time, the speed control unit controls the speed of the vehicle such that the vehicle enables to make a lane change to the second lane behind the another vehicle,
• wherein, in a case where the first arrival time is shorter than the second arrival time and a difference between the second arrival time and the first arrival time is greater than a prescribed time, the speed control unit controls the speed of the vehicle such that the vehicle enables to make a lane change to the second lane ahead of the another vehicle in a case where the first arrival time is shorter than the second arrival time, and configured to control the speed of the vehicle such that the vehicle enables to make a lane change to the second lane behind the another vehicle, and
• wherein, in a case where the first arrival time is shorter than the second arrival time and the difference between the second arrival time and the first arrival time is within the prescribed time, the speed control unit controls the speed of the vehicle according to the first arrival time, the second arrival time, and the weight of the load that the vehicle is loaded with.