Not trying to be a know-it-all, but I'd like to offer my 2 cents because I've done different kinds of street riding as well as different kinds of track riding.
I started out on 2 wheels as a bicyclist in NYC. I rode all over town, from horse trails in parks to zigzagging my way through cab traffic in Manhattan. That taught me, among other things, how to ride in very aggressive city traffic. It was 85% situational awareness and 15% bicycle control.
I then got my first motorcycle: a Seca II. City riding became a much smaller headache. I was able to apply everything I knew from cycling to the motorcycle with the exception of dealing with a heavier machine. But at the same time I had acceleration on tap and the whole thing just felt way easier.
My glaring weakness was hard braking in the dry -- I was still trying to use both brakes and getting myself sidways like I always did on the bicycle. Needless to say, that was a bad idea at higher speeds. I did however manage to save a few unintentional slides, including front wheel lock-ups that I don't think I would have been able to save without the quick reactions and constant state of high alert learned from ever-changing city traffic.
I then moved on to my first sportbike: an F3. Contrary to what I thought might happen, I felt way more comfortable on it in all aspects of riding. And of course, I immediately started doing squiddly things on the street, including going into the hills to "practice".
Mercifully, someone told me to go and check out a trackday. My first exposure to the track was cornerworking. And I gotta tell ya -- I learned a ton. Just from watching bikes go by, a number of things became apparent:
- I was not the fastest rider in the world
- smoothness leads to speed
- speed and safety can be attained from a similar set of skills
I signed up and did my first trackday. Despite highsiding at the end of the day on cold tires, I learned more about bike control than I did my entire squiddly riding career up to that point. The biggest things I tapped into was how to use my eyes and how to use my body. It was like I had been living in a small cramped room for years and suddenly someone opened a door to the outside -- the biggest thing I learned was how little I actually knew.
I then took up some Keith Code books and hit more trackdays, trying to apply everything I digested from the books. It was definitely addictive -- every time I was out-there, I came away with huge improvements. And the best part was that the better I did, the slower it felt. I became calm and calculating while riding as opposed to "pushing" and gritting my teeth.
I decided it was high time I tried to compete. By that point I had converted the F3 to 100% track and only rode street on occasion on borrowed bikes. When I did that, I was both more freaked out by all the unpredictable crap going on around me, and at the same time more collected mentally. I had 2 close calls caused by cars pulling into my path that I got out of through extra-quick countersteering. I knew that without my still limited track experience, I would have tried brakes and most likely gotten seriously hurt or worse in both situations. The cool thing was that in both cases I did the right thing without thinking. Still, those experiences made me even more hesitant to ride street.
A few years of racing in sunny CA followed that with occasional dabbling in street riding. I kind of enjoyed riding through SF, mostly because it was so different from the track and reminded me of "the good old days". Jumping a sportbike through intersections going up the SF hills was definitely the dog's bollocks as they say. Thinking back, I should have probably gotten myself a motard.
After some more on-and-off racing and even more sparse street riding, I ended up on the east coast in the burbs. I fixed up a junky EX500 for the street and got an F4i for racing. Riding the EX on local roads was the first time I truly enjoyed competent street riding with the ego as well as the traffic dangers mostly in check. I was definitely a lot more in control of how much I wanted to push the envelope at any given moment, something I was blissfully unaware of when I was trying to be a hero on the F3 in the hills. I do admit that the point of the racer's overconfidence holds true. I never bothered to get new tires of the EX, which had a nice square bald piece of rubber you'd be hard pressed to call a tire on the back. In the rain, things were definitely dicey and I was basically unnecessarily taking chances. I'm not doing that anymore.
I had one interesting experience on that bike that kinda took me full circle. Last year I rode it down to NYC and hit Manhattan traffic on the highway and in the streets at the peak of afternoon rush hour. My crazy-close street riding skills were a bit rusty at that point. But I dug deep and remembered most of it getting there in one piece and kind of having fun by then.
So after all the rambling, what's the point? I think part of the confusion about track and street skills overlap is that it's all about what any one individual is lacking. Undoubtedly it's possible to be a pro in any niche environment and be a poor rider in others (the late great Joey Dunlop never achieved greatness as a closed circuit racer). And undoubtedly there are ways to leverage what you know as you adapt to new situations. When I moved to CA, even going from east coast tracks to west coast tracks was a bit of a shock to the system. But I'd say the more one knows, the better one is prepared for whatever new challenges await, in riding and in life in general. I think the most important thing is to understand your own limitations and learn how to learn. Remember, we're all still learning to ride!