rakuwoman13- Your German Shepard would be a great deterent. You can still train your dog, my Aussie is 5 and I have
(almost) trained her to "heel" on the left and "side" on the right. There is also a leash that can be hooked up to your bike in the back. I can not think of the name of it maybe someone out there knows. Both you and your shepard would benefit from riding together. Stay safe!