I'm not going to judge the decision to swerve or not swerve. I drive around 40K miles per year, sometimes towing and sometimes not. I'd like to think that I've ran a great number of scenarios through my head and I'm prepared for most of them, but reality is that you really don't likely have even 1.5 seconds to figure it out. Your reaction must take place in like 1/2 a second or less. Despite the fact that I've ran scenarios through my mind hundreds of times over, I've encountered times when my instinct said SWERVE even though I immediately knew it was wrong.
Several years ago, I was in the middle lane of the interstate going between 75 to 80 MPH. When I crested a hill, all I saw was BRAKE LIGHTS and stopped traffic. I had no time to even think...it was either swerve left or right or have a guaranteed collision. I instinctively swerved left and fortunately there was no one there. But, there was a car right behind me riding my tail that didn't fair so well. He swerved left...WAAAAYYYY left and struck the guard rail.
So about the propane...
Leaking propane from a tank is not necessarily going to allow the backflow of a flame into the tank. I don't think the OP was in any danger whatsover due to the propane situation...no more danger than what he would have been in due the accident anyway.
