Abstract: When a preceding vehicle in a driving lane is adequately caught insight, a target vehicle speed is calculated by a calculated value based on an adequate vehicle-to-vehicle distance to the preceding vehicle, and it is checked whether or not a gradient for determining whether the road on which the vehicle is running on a downhill road or an uphill road should be performed. If it is determined that the road is the downhill road or the uphill road, the target vehicle speed is corrected according to the gradient. The indicated vehicle speed and the actual speed are adequately adjusted according to the road gradient, and an adequate vehicle-to-vehicle distance to the preceding vehicle is maintained to realize a consistent follow running.

Abstract: A track managing unit manages data tracks stored in a predetermined data region and a freely-usable part managing unit manages freely-usable parts in the predetermined data region. A restoring unit causes the track managing unit to manage the freely-usable parts managed by the freely-usable part managing unit. Thus, parts, which once had a data deletion operation, labeled as freely-usable parts and thus managed by the freely-usable part managing unit, may then be relabeled as data tracks and thus managed by the track managing unit. As a result, data which could not be reproduced in the apparatus and method in the related art can be restored and thus reproduced. When causing the track managing unit to manage, as other tracks, a plurality of parts which have been managed by the freely-usable managing unit, the restoring unit may cause the track managing unit to manage, as another track individually, each part of the plurality of parts.