Folks: New to the forum. I tried to search on this subject, but for the life of me could not find a general search feature. So if this is already well covered, please forgive me and point me in the right direction. Background: I have a male Shelty who is 4 years old. He is exercised eacy day on a 3 mile walk, 7 days a week. Often a few more times around the block every day. When I do my daily walks, the first mile or so is off leash in a field where he can run wild for even more exercise. His name is Rusty--as seen in my profile picture. Healthy, wonderful family pet. Never aggressive with anyone--but he likes his space (which we are fine with). He was well socialized as a puppy and does well with other dogs and people of all types. Being a Shelty, he can be a bit of a barker, if he wants your attention, but never one to bite. Issue/Concern: Again, being a Shelty, he has a tendcy to be a bit "skiddish" with loud sounds. Meaning he doesn't do well with lawn mowers or leaf blowers. Fireworks, he is ok, odly enough. However, any loud car or motorbike puts him into orbit. If he hears a Harley bike even 1/2 a mile away, he takes notice and waits for it. The trouble is, most cars he anticipates their arrival and as they pass, tries to give chase with wild barking and pulling at the leash. It has gotten so bad that many times in the back yard he will wait at one side fence to listen for a car and then run behind the house to the other side of the home to bark as it passes the home. To add confusion to this issue, he LOVES car rides. All I have to say is "Want to go for a ride" and he immediately heads for the garage door with anticipation. He sits in the car seat with head out the window and would do this for hours. I've often wondered if his desire to chase/bark is because he wants to be inside the car. Hard to tell. What I've done: I've tried the training/behavior modification of treats with cars. For example, when a car comes and I see him look back or anticipate it, I show him I have a treat; tell him to site, which he does; then only reward it to him if he doesn't bark and give chase. This works most times. Trouble is, if I fail to bring treats with me on a walk, he's back to barking and chasing (on leash of course but he lunges like mad). Key observed behavior: When I do have treats and I have him sit before a car/truck arrives, I've noticed that if the vehicle is exceptional large or noisy, say a loud diesel or truck with a louder trailer, when it passes he will cower a bit in fear. Meaning leans towards me and looks back nervously. Thus, I often think his continual chase and bark instinct at cars started as a reaction of fear and now is becoming more of an excitable behavior. Finally, I should add that as a puppy, say around month 4 to 6, I attempted at least 3 times to condition him to cars. I took him to busy intersection where there was grass near by and sat him down with me to watch cars and get used to the noise. I stayed a good 50 to 100 feet away from the intersection and slowly moved closer over time. I thought this was good to help him get comfortable with car noises. Perhaps it only instilled fear. As I said in the beginning, I walk him daily for 3 miles. Much of it is off-road on trails but each day I do like to return on sidewalks and often have to walk when cars are passing. I really wish I could solve this issue so my walks could be more enjoyable--and more importantly, that he wouldn't chase/bark when in the backyard and normal traffic passes our house. We don't live off of a really busy street, but the occasional car often results in a bark and chase moment.