OP I really found CBT helped massively with this sort of thing. Give yourself time to process the event rationally as well as emotionally, and also talk to yourself in a caring way and gently nudge yourself back on track.
It's about the soundtrack in our heads and interrupting the negatibve intrusive one.
So in your case, you might pull up somewhere and acknowledge your reaction: Wow, I am incredibly distressed by that. It deeply shocked me mentally, physically and emotionally.
Then self care - check any physical improvements you could make: I feel a bit shaky. I might phone and say I'll be ten minutes late, then buy a cup of tea. Or if you are shivering, put an extra layer on for a moment. Etc. At this stage it's important not to make a drama out of it. E.g. if you are calling to say you;re running late donm;t go into detail as that just reinforces the fear and feeling you can;t cope. You are actually coping by giving yourself a micro-break and taking care of yourself so you can get back on track with a normal day
Then do the rational thinking. "this was scary because it hasn't happened before. It hasn't happened because I am a good and careful driver. Everyone in the entire world makes mistakes sometimes or has accidents happen that someone else is responsible for. this is normal and natural and I can cope with it. It isn't nice but it isn't a sign of anything more than normal life with its hiccups. This was a hiccup.
Then you go about your day. If you find your mind playing tricks on you, syaing: Oh how scary. Be afraid! or You dangerous driver, you shouldn;t be on the road! just interrupt and get back on track: 'Scary, yes, but done now. I survived and handled it well.' Or 'Yes, momentarily dangerous but incredibly unusual and I handled it fine. All is well now.'
Something happened to a family member during lockdown that profoundly upset me. I found I was anxious 24/7. Waking at 3 am and unable to sleep again then dragging through the days with exhaustion on top of the anxiety. Doing CBT to rationalise really helped both me and the family member as my anxiety didn't help them at all, just added to their burden of stress.
Does that sort of thing sound like it might help?