Dog nervous of people coming from behind

Hi

I have a 1 1/2 yr old Jack russell, recently she has started to bark and run after cars, cyclist or joggers that come up from behind us, she has no problem if they come towards us. I have to keep her on the lead now when we are out walking as we go along a canal path, it is the only wy I can stop her jumping up at joggers or cyclists.

Has anyone got ny thoughts on how I can get her no to be affected by them?

Actually, it's a good idea(and a law most places) to keep your
dog on lead when you walk them outdoors.

my old dog had the same thing. She could only fear in one ear so she didn't know where sounds were coming from. When things came from behind her she'd startle and nip.