I can understand your fear, but dogs should not be chained at all. Where I live it's even illegal to keep a dog on a chain because it's considered animal cruelty.

Dogs cannot understand that you want to protect them by keeping them on a chain. They also cannot understand why they cannot move to a certain place if there's no wall or obstacle in front of them. Or why they cannot chase the man or other dog away thats so close and yet cannot be reached. Being on a chain is not comprahendable for dogs and their phychological development will suffer. Many will also develop problematic behavior like agression, constant barking or compulsive behavior because of that. They might even hurt themselves by pulling too hard on the chain. (That's why it's illegal to keep dogs on a chain in my country.)

The best solution would be keeping him behind a fence. If that's not possible, I suggest you rather teach him that the highway is dangerous and that he should never go there. You do that by going on a walk with him near the highway (maybe 10 meters away) and

• Every time he walks directly towards the highway, you tell him "No!" and pull him away from there.
• Every time he walks away from the highway or he walks next to you opposite of the highway you reward him by telling him how good he is.
• Every other time you can just ignore him and continnue walking.

His dog mother would have done the same thing. She would have stood between him and the highway and stopped him from going there. It will take some repititions, but eventually he will understand that he's not supposed to go there.

I can understand your fear, but dogs should not be chained at all. Where I live it's even illegal to keep a dog on a chain because it's considered animal cruelty.

Dogs cannot understand that you want to protect them by keeping them on a chain. They also cannot understand why they cannot move to a certain place if there's no wall or obstacle in front of them. Or why they cannot chase the man or other dog away that's so close and yet cannot be reached. Being on a chain is not comprehensible for dogs and their psychological development will suffer. Many will also develop problematic behavior like aggression, constant barking or compulsive behavior because of that. They might even hurt themselves by pulling too hard on the chain. (That's why it's illegal to keep dogs on a chain in my country.)

The best solution would be keeping him behind a fence. If that's not possible, I suggest you rather teach him that the highway is dangerous and that he should never go there. You do that by going on a walk with him near the highway (maybe 10 meters away) and

• Every time he walks directly towards the highway, you tell him "No!" and pull him away from there.
• Every time he walks away from the highway or he walks next to you opposite of the highway you reward him by telling him how good he is.
• Every other time you can just ignore him and continue walking.

His dog mother would have done the same thing. She would have stood between him and the highway and stopped him from going there. It will take some repetitions, but eventually he will understand that he's not supposed to go there.