There are a lot of reasons why you should be very careful when try to approach a frightened stray. One of the reasons is that you don’t know what is the dog’s history. In case the dog was abused he can get scared and because of the fear approaching him can be dangerous.
The best option is to call a professional. They have experience and their methods are always the best.
If you will ever be in a situation where you will really need to approach a stray before someone with experience arrives this would be the best approach. The woman in the video below, works with the program “Pitbulls and Parolees”. Being a dog rescuer she demonstrated the best way to approach a frightened stray. Watch the video to see her strategy.