Now your getting the idea Claire. Yes, now your on the right track. Exposure is about building up, not avoiding and not being in control. Yes, you can control your exposure is what I refer to, ie. you MUST expose yourself beyond your comfort levels, NOT within or to your comfort level.
Often when trauma is involved, the problem is quite amplified, ie. with yourself you may not currently be able to cross a road at all unless with another person! Then again, you might, but you get panicked about it. If you can do it, then go and do it over and over again, until you get so drained that your brain just doesn't care anymore about crossing the road. If you can't cross the road by yourself, then what I have said previously would apply, ie. you build yourself up, you find things to focus upon, etc... a staged buildup. If a person had an extreme fear of crossing the road and were incapable of crossing a road by themselves, and dissociated even with another person holding them for support, then going out and crossing the road constantly would most likely make them collapse or have a serious breakdown. If a person could cross the road, but just gets symptom outbursts a couple days later, but can cross the road by themselves without too much issue, then you would send them out to just continually cross a road, time after time, until such time as they did get close to physically ill, but by the end of it their brain would have learnt that it no longer needs to fear crossing the road. Yes, that person would still have serious side effects days later with symptoms, but they would dissipate soon enough and their personal boundaries of crossing the road would have been pushed far beyond what they had.
It is an individual approach, and each persons ability and symptoms are different. You must look at the severity of your inability to cope with it, and determine whether you would just go rapid at the problem and hit it constantly until you fell over with exhaustion, or whether you would need a staged approach for weeks, months even, until the time they could hit it over and over til exhaustion, just to reinforce the new boundary to their brain.
You want to expose yourself to screaching, then go buy "Tokyo Drift" from the Fast and Furious series, as that contains lots of it, and literally force yourself to watch it or listen to it even as you plod around the house, play it over and over, until your mind learns that the sound by itself is not going to hurt you. Then you might go to a race meeting, so you see real cars with real screeching... just to push your boundaries a bit further again. You would eventually build yourself up to such a point where you would get in a car and go and intentionally speed up, break hard to screech, and repeat it over and over. Staged progression generally works best.