I've made many trips where we were running two vehicles. I always had the DW follow about 1/4 mile behind me. This gives her plenty of time to adjust to any lane changes I make and I can monitor her fairly well in my mirrors and go back if she disappears for a while. She can catch up to me and blink her lights if I have a tire going bad or something. Like me, you've seen the families moving across country with the husband driving the Uhaul truck and the DW following 20' behind giving her no time to react and making it difficult for faster vehicles to get by them.