Pretzel is a 5 month old border collie puppy who is dangerously lunging at cars. This is due to the breed's hardwired drive to herd livestock. This is a dangerous problem for both the dog and the handler. For the past week and a half, my boyfriend Steve and I have been training her with various exercises to acclimate her to cars, dogs, and strangers. Although she has improved tremendously, she should carefully be monitored while being walked around these trigger stimuli. I try to keep these exercises at short durations, depending how she is responding that day. Anywhere from 15 min. to 1 hour. Hope this helps.