Image Classification using Single Class Dataset using Transfer Learning
You can use Tensorflow Object Detection API. 

In the API, you dont have to have 2 or more labels. It can be used with only one label. By transforming images to tfrecords, you can train and predict other images. The prediction will you give you bounding boxes and probabilities that how much an object identified as a vehicle.

The challenge in here is labeling object locations on the images. LabelImg is a great tool for that.

Hope it helps!