Yes, this behavior needs to be stopped immediately because the swan will eventually be killed by a car or a predator that attacks the swan away from the pond.

One of the reasons that the bird may be wandering is that it is migration time and all birds have an innate need to migrate. So, captive swans that cannot fly will "migrate" by walking away from the habitat.

There are only two ways you are going to successfully stop this behavior. Fence the habitat near the pond so that the swans cannot cross over or near the road. This will be the most permanent solution.

The second solution is to capture the swan once it leaves its immediate and permissive area to wander. Once it reaches its non-permitted area, capture the swan or herd him back to his area. Once or twice capturing the swan, he will get the picture that he does not want to get picked-up by you or anyone else and he will stay near his permitted area. He may get upset with you capturing him, but it will only last about 2 weeks at the most. He will still return to you for feeding, just not close enough to capture. In the grand scheme of things, getting upset is much better than being seriously injured or killed by a car or predator. The Regal Swan