Originally Posted by
bluefoxicy
In my ideal situation, the roads should support enough flow that bicycles and cars can, at the worst, both move out of each others' way: the cyclist has an extra wide right lane and should go to the right to allow cars to pass when necessary, but the motorist should pass in the left edge of the lane or partially change lanes (with signal) when clear. In a multi-lane road with appropriately (Americanly) wide lanes, this should always be feasible even in heavy traffic if both the motorists and the cyclists cooperate. In European style narrow roads ... European roads are designed better, with visibility and such in mind to make it easier to safely pass, and accommodate bicycles and pedestrians. Wide American lanes work to our advantage here.
Living and cycling a lot in London (England) a lot of our roads are fairly narrow but still usually wide enough for a car to pass a cyclist, as long as both are sensible. In case you didn't already know we drive on the left in England so flip left/right as appropriate
Outside the cities we have a few roads that are narrow enough that a car couldn't safely pass a bike without crossing into the other lane (i.e. into the path of oncoming traffic) and enough traffic that a cyclist on such a road would be a nuisance to just about every road user stuck behind them. For good measure some of these roads don't have anywhere suitable for a slower cyclist to pull over and let cars pass every once in a while. On a road like that it's hard to see a bike doing 20mph or less and traffic wanting to (legally) do 50-60mph getting on too well together in the same space.
What I've seen of American roads is that most of them are hugely wide by UK standards. Admittedly American cars are also typically larger than ours (and you guys do like pickups and 4x4s, which are much larger than most of our cars) but the roads I've seen in the US (which cover about 13 states from CT down to SC) is that there should be more than enough space. The thing that would put me off cycling on a lot of American roads is the same as in the UK - in the more rural areas I'd rather not be sharing a road with a 55mph speed limit with honking great trucks that aren't expecting to see me there. That said in the parts of PA I'm familiar with the logging trucks and Amish buggies manage to share the road, so it's hard to see why they couldn't also share the road with a bike (probably faster than a buggy and definitely narrower).
I know it's not hard data but hopefully it has some use to you.