I voted
metropolitan city streets (with heavy traffic), though I usually commute early in the morning before traffic gets heavy, and I ride in the reverse commute direction from downtown to the suburbs. I also voted
Other because much of my riding, 14 miles one way in total, is on light commercial and residential streets in Boston and adjacent suburbs. I did not vote MUP, because that is my least traveled route, about one mile at most.
All in all, it's a most safe and desirable route, though I did get hit from behind by a careless driver on a reasonably safe segment. Not to sound too morose, but I recently posted elsewhere:
Originally Posted by
Jim from Boston
...In any case, I was still hit by a careless driver on a wide, lightly-traveled section last year, losing three months of work. So I am
reluctant to encourage anyone to cycle-commute (or even ride a bike in traffic

)
though I heartily support even the most adventuresome, yet careful cyclist.
One major confidence booster IMO, beside hi-visibility lights and clothing, safe routes, and prudent cycling behavior, is use of a rear-view mirror. In fact, I wear
two, left
and right...
I still do cycle commute though, and finally, I have the opportunity of taking the train from my workplace to a station within 2 miles of my home, when the city streets are more heavily traveled.