The present invention relates to a travel support device, a travel support method, and a drive support system that support travel from a current location to a destination of a vehicle provided with an internal combustion engine and a motor as drive sources. 
As a vehicle capable of selectively switching among a plurality of travel modes, a hybrid vehicle, which uses both an internal combustion engine and a motor as its drive sources, is known.  As the travel modes, the hybrid vehicle has an electric vehicle (EV) travel mode that places priority on EV travel, in which the internal combustion engine is stopped and only the motor is used to travel, a hybrid vehicle (HV) travel mode that places priority on HV travel, in which the internal combustion engine and the motor are used to travel.  The EV travel mode is a travel mode in which the remaining energy charge of the battery is not maintained and the HV travel mode is a travel mode in which the remaining energy charge of the battery is maintained.  Also, a travel support device that is installed in the hybrid vehicle and includes a navigation system provides support by calculating a travel route from the current location to a destination based on information such as map information and road traffic information and selecting the travel mode to be applied to each of a plurality of sections in the travel route.  For example, Japanese Laid-Open Patent Publication No.  2009-12605 discloses an example of a vehicle controller having such a travel support function. 
In the vehicle controller described in Japanese Laid-Open Patent Publication No.  2009-12605, the travel modes of the respective sections in the travel route are set in consideration of the battery energy balance for the entire travel route so that the remaining energy charge of the battery, which is a rechargeable battery, becomes zero at the point of arrival at the destination.  However, in a section in which traffic congestion is occurring, the road load tends to become lower than that during normal traveling so that the battery energy cannot be consumed completely and the remaining battery charge may thus not become zero at the point of arrival at the destination. 
Such a problem is generally common to devices and methods that assign travel modes to respective sections in a travel route for a vehicle having a plurality of travel modes that differ in battery energy balance.