A cat crosses the lane and your dog locks on. The cat needs a way out, and your dog may hurt themselves or pull you into danger if the chase begins. Keep your dog on a secure lead in places where cats appear. Do not let them "have one chase" for fun.
Choose routes with clear sightlines and room to turn away. Practice a cheerful "this way" cue on quiet walks, rewarding your dog for turning with you. When you notice a cat at a distance and your dog is still able to respond, use the cue and leave. If they are staring hard or pulling, create distance and do not repeat the cue over and over. A long line is not appropriate near roads or cats with no safe escape.
Give chasing a safe outlet
Many dogs enjoy moving toys or scent games. Offer appropriate play away from wildlife and cats, and practice recall in secure spaces with easy distractions. Build gradually. The goal is not to assume a dog who recalls from a toy will recall from a cat tomorrow, management remains in place while the skill grows.
If your dog lives with a cat, the risk is different from an outdoor sighting. Keep them separated when you cannot supervise, give the cat safe high and separate areas, and seek individual guidance if your dog fixates or tries to catch them. Don't assume that a dog who ignores the family cat is safe with unfamiliar cats outside, or the reverse.
If your dog has reached or injured a cat, or you cannot control the lead safely, ask a qualified, reward-based behavior professional for help. Every avoided chase gives both animals a safer day. For more on managing the urge to chase moving animals, see the dog-chasing guide, keep cats safe with a secure lead and enough space
Sources: Dogs Trust: How to stop your dog chasing cars, bikes and animals. Dogs Trust: How to help your dog and cat live together safely.