Your dog is quiet while the car moves, then whines at every red light. They may anticipate a destination, notice people passing close to the window, or feel unwell. Watch whether the whining starts at the first light, only near the park, or after a long drive. Drooling, lip licking, vomiting, or restlessness can point to motion sickness or anxiety, and a veterinarian can help assess those possibilities.
Secure your dog in an appropriate travel crate or car harness. Never let them roam toward the driver or lean out of a window. Do not turn around to train at a junction or offer treats while you need to focus on driving. If your dog is panicking or repeatedly sick, pause nonessential car trips and get veterinary guidance.
Work while parked safely
With another adult available to handle the dog, practice sitting in a stationary car where the dog feels comfortable. Reward a moment of relaxed behavior, then end before they become worried. Later, take a very short, easy trip and stop in a safe parking spot, rewarding only while the vehicle is safely parked and the handler can attend to the dog. If approaching traffic or pedestrians seem to be the trigger, choose quieter routes and consider a safe visual screen that does not affect the driver's visibility.
Vary destinations so every stop does not mean the same exciting or unpleasant event. If the dog becomes more distressed during motion or after eating, do not try to train through nausea. Ask your veterinarian what to do first. The best plan depends on whether the stop means "we're there," "someone is near," or "I feel sick." After ruling out motion sickness or distress, the everyday dog-training habits guide can help you build a calmer pause routine on parked-car practice. Do not train while driving.
Sources: VCA Animal Hospitals: Dog Behavior and Training - Air and Car Travel. VCA Animal Hospitals: Motion Sickness in Dogs.