[admiral_biatch]

In my opinion isolating separate transportation modes is only good if it is complete isolation but that's never feasible in a city. Too expensive and space-inefficient to make every intersection collision-free for cars, bikes and pedestrians.

If you separate cars, bikes and pedestrians most of the time but their paths cross at intersections then you have a problem because drivers might not expect a sudden bike lane out of nowhere. It's better to have the bike lane on the street so that cars see it all the time. This makes them drive slower and more carefully because they expect bikes to show up there.

I don't have data to back this up although I vaguely remember reading about it in "Streetfight" by Janette Sadik-Khan. If I recall correctly introduction of unseparated bike lanes in New York City didn't increase bike fatalities despite increasing the number of bikers and it also decreased number of pedestrian fatalities thanks to cars driving slower because of bikes. Of course the article shows that now the pedestrian deaths increased so it might have been a premature conclusion on Sadik-Khans part.

[jnty]

Of course drivers in cities do expect 'bikes coming out of nowhere' because, unless you literally separate bikes with a 6ft wall, you can in fact still see them despite there being kerb-separation in place. At car/bike junctions with poor visibility the same interventions are available as for car junctions with poor visibility.

If you've ever seen a mangled barrier by the side of a road, you'll understand why encouraging humans into the road as a traffic calming strategy is rather problematic.

Enlightened cities such as those in the Netherlands tend to take a risk-elimination approach - residential streets will be designed to keep speeds low, and neighbourhoods designed so that through-traffic doesn't try to take shortcuts along them. This makes it safe for cyclists to use the roads without special infrastructure. Only busier main roads have infrastructure. This is hard to imagine in the US where many cities in the US seem unfamiliar with the concept of any road not being a busy main road!

[admiral_biatch]

Where I live (Poland) it's not uncommon for a bike lane to be effectively a part of the sidewalk with trees and parked cars between the sidewalk and the road so it's not that obvious if you're visible to drivers or not.

I agree that putting unprotected humans on the road should happen only after other traffic calming measures have been put in place.

Regarding your last remark. There are basically two styles of bike infrastructure. You described the dutch way quite well. But there is also a Copenhagen style of bike infrastructure where it's directly by the road. Sometimes separated by the curb but still on the road. https://goo.gl/maps/QWTfALXSbsj

I won't judge which style is better. It probably depends on the city.

More about differences between Amsterdam and Copenhagen styles https://robertweetman.wordpress.com/2017/11/04/amsterdam-vs-...

[Someone]

”but their paths cross at intersections then you have a problem because drivers might not expect a sudden bike lane out of nowhere.”

If you design your intersections correctly, cyclists do not appear out of nowhere, they always intersect at right angles with the car lane (https://bicycledutch.wordpress.com/2014/02/23/junction-desig...). That hugely increases visibility of cyclists for car drivers and vice versa, and makes eye contact possible.

[maxsilver]

> but that's never feasible in a city.

That's kind of funny to hear, because I was going to use real-world Chicago and Seoul as practical examples of this already existing in cities today.

Chicago Loop has a dual-layer approach (where faster moving cars are on the ground floor, but a "second street level" is directly above them, for pedestrians + buses). It's not an exact match (cars can drive on both levels, those lanes should all exist on one level), but it's pretty close to this idea already in practice.

On the opposite side, Seoul has a "pedestrian highway" slung above 8ish lanes of car traffic below, which is a cheaper (although less effective) version of the same idea.

[lostlogin]

Paris has it pretty good in the central areas. Wide roads with (outside in) footpaths, cycle lane, road, then a central section with tram, trees and garden or parking. Having massively wide roads helps.

[anonymou2]

The current traffic system is the best known way to share the roadways among different types of vehicles, all subject to the same rules. Trying to construct a set of grids for different types of vehicles which interact at certain points is silly, consider what happens when new types of vehicles come into being, like electric scooters, are you going to construct yet another "independent" grid for them?

[admiral_biatch]

I agree with you. I'm not in favor of separation precisely because it's unrealistic in the city.

[rconti]

Plus, separating all of this infrastructure takes space, which in turn makes everything less walkable. In cities, there really need to be fewer car lanes for it to work.