Keeping your dog safe during nighttime walks requires a little preparation on your part. You should use a short leash that will not allow your dog to scamper out into the street where he might get hit by a car or truck. A short leash while walking your dog is always safer than a long leash but even more so at night when headlights can confuse your pet, and he might inadvertently dart out into the street to check out the lights.
During the day, you can take a walk with your dog in nice fields without being too concerned with other inhabitants of the field. At night, you might not see a squirrel or a groundhog or mole, but your pet might. A pet darting after a one of those creatures can find himself being bitten if he catches it. It is always wise to keep your pet walking on sidewalks and areas that not occupied by wild creatures.
Another safety precaution is to stay away from parking lots at night. You have no way of knowing when a car may suddenly pull out even if you assume that none of the cars are occupied. If your dog has chosen a particular car to relieve himself, he might just get run over by it if the driver was in the car and backing out. Parking lots or any parked cars are no place for your dog to be sniffing near.
Dogs love to sniff. At night, you might not know what they are sniffing since they are closer to the ground than you. Keep to a familiar path and let your dog develop a habit of which poles and shrubs he is allowed to sniff. As an added precaution, you could carry a night stick just in case an unleashed dog crosses your path and decides to challenge your dog.
If challenged your dog may attack and get bitten. You want to avoid that situation by standing still, keeping a tight grip on your dogs leash and telling the other dog to scat while holding the stick out where he can see it. Other than that, you could wear a dog whistle when walking at night. Blowing on the dog whistle when accosted by a stray dog will keep the other dog from challenging your pet.
Just in case your dog breaks his leash and runs off, you should keep a collar on your dog that has reflective metal worked into the leather or Velcro. Being able to spot your dog in the dark just might save his life especially if he runs off in winter and can't be found till morning. A dog lost at night during the winter stands a pretty good chance of freezing to death.