In an apparatus, a first obtainer obtains a first travelling-condition parameter of a target vehicle. The first travelling-condition parameter shows one or more conditions under which the target vehicle is travelling on the road. A second obtainer obtains a second travelling-condition parameter of a preceding vehicle travelling on the road immediately ahead of the target vehicle. The second travelling-condition parameter shows one or more conditions under which the preceding vehicle is travelling on the road. A deviation calculator calculates a deviation between the first and second travelling-condition parameters. A behavior determiner determines a recommended behavior of the target vehicle in response to the calculated deviation. A controller controls a device, which is associated with a behavior of the target vehicle, according to the recommended behavior.