In the dark model there are no trucks.I'd say "car" and "Car" or even "car" and "Vehicle". That way you could add trucks as well and just use a single label.
Dark | Total Images | Train Images | Val Images | Image Total |
Bicycle | 652 | 624 | 28 | 652 |
Bus | 526 | 504 | 22 | 526 |
Car | 637 | 610 | 27 | 637 |
Cat | 727 | 696 | 31 | 727 |
Dog | 796 | 762 | 34 | 796 |
Motorbike | 502 | 481 | 21 | 502 |
People | 608 | 582 | 26 | 608 |