I've cut quite a few car sequences over the years, here's what I'd do – For your onboard sequence I assume the cars slowly cruising by are going in the same direction as your main car. I've always had good luck … Great recordings if your car isn't doing anything unusual but I find them not quirky or fun enough if your car is doing strange stuff. Like that other guy I'm also not … Oddly enough, engines can be reversed and they're quite forgiving in that respect. And as I heard Jay mention … …

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Weird car actions? – Social Sound Design