How do the bike lanes accomplish either of these things? By cyclists not having "to worry about being hit from behind", and by motorists not having "to slow down" to pass, I take it you mean that there is ample room in the right lane for the cyclist and overtaking traffic to share it. Ok, the lane is wide enough to be shared easily. That is just to say something about the width of the roadway, not the bike lane.

Where I lived once, I was near the border between two cities. A wide road ran in each city, crossing this border. In one city, there was a bike lane on the right hand side of the road. In the other city, there was no bike lane, and the road was otherwise unchanged. Was it any more comfortable to ride in the bike-laned city than in the other city? No. Not at all.

In fact, one of the best places to ride is on a busy street that allows parking on the right hand side of the road, in the right-most lane. I'm talking about streets with no bike lanes, of course. Some streets are set up like this at non-rush hours, and in NYC some streets are always like this, from what I could tell.

It's nice to ride in the space between the left side of parked cars and the traffic lane to the left. (I did it on the motorcycle, too, when traffic was heavy.) Since the street is busy, you get the lights more often than on bike-laned streets, too. Again, this is just to say that when there is an extra wide right hand traffic lane, it's easier to cycle. This is not a point about bike lanes.

But what would the disadvantages be of bike lanes on wide roads? They don't do any harm, do they?

Well, I think they do. For one thing, the city's got to paint the things, and maintain the paint. That's not a lot of money by road maintenance standards, of course, but it's more than not painting at all. It would add up to a lot of money too if many streets had the lanes. Then people who aren't that comfortable riding in traffic get the idea that there's something especially safe about the bike laned road, as opposed to other roads. So, they're not all that comfortable riding on other, perfectly useable roads because those roads *don't* have bike lanes. And these riders go out on roads without knowing how to deal with intersections properly, just because there are bike lanes. Some motorists get the idea that cyclists don't belong on roads without bike lanes. And so on.

I've just never been convinced that alleged benefit of "encouraging" cycling is worth the trouble of bike lanes. I can't say, either, that the problems of bike lanes have made my life a lot harder in places where they do exist, though.