Terminal device, rearward server, in-vehicle transponder, determination system, determination method, and program

This terminal device is provided with: a candidate acquisition unit that, when a candidate determination unit for determining whether or not there is a possibility that a vehicle is performing reverse travel has determined that there is a possibility that the vehicle is performing reverse travel, acquires reverse travel candidate information including traveling direction information and position information of the vehicle; and a candidate notification unit for providing notification of the reverse travel candidate information to a rearward server that, on the basis of the reverse travel candidate information, determines whether or not the vehicle is performing reverse travel.