Fence height

The proposed fence would be 4ft high. When motivated, some dogs can jump higher than this... these fences would be close to highly-trafficked roads. 
 This dog jumping an 8ft fence is lucky that there is no road nearby - as you can see it's harder to control a dog by voice who is running away from you:

Here's a thoughtful dog trainer with advice for dog owners who would prefer their dogs don't jump fences. He starts with... yes "make the fence higher". He says that a 4ft fence won't be tall enough for big dogs.

...yet a dog doesn't have to be huge to jump that high. Here's a medium-size dog and a 5ft fence:

All right, for the lighter side of things. Fortunately all these dogs are in the "eastern region" so we don't have to contend with their skills in Oakland! But what fun to watch - championship dog-jumping!