Many dark hours I’ve been thinking about this: Why do we have two-way
streets? :smack: I can only think of one advantage (if you’re unfamiliar with the
area you don’t need to consult a map), and many disadvantages (the really
cool head-on collisions that prove momentum = mass x velocity squared;
pedestrians have to look both ways; the complex traffic pattern at an
intersection where both roads are two-way)… And of course, I’m not
talking about remote or mountainous parts of the country where two separate
one-way roads would be much more expensive to build than a single 2-way;
there, it makes perfect sense. But in the city?
Well:
1.) Because there’s an equal chance that motorists would want to go either direction (or come back for that matter).
2.) Because one way patterns work best in highly dense grid patterns, because if the street goes the wrong way, you don’t have to go very far to turn the block and head in the direction you want to go.
3.) Because many suburban streets wind around and connect in odd patterns, which make one way street patterns untenable (except for a few streets here and there).
4.) Because most streets are wide enough to support 2 way traffic.
5.) Most of all, because 1 way street patterns can be a pain in the butt.
FWIW:
Downtown Philly, USA is almost exclusively one way streets, and based on my travel experience, Philly is relatively easy to navigate…and traffic stays moving a bit better.
The real source of traffic is usually on Broad st, one of the few two-way streets.
I wonder if there are any statistics for auto accidents comparing two-way and one-way streets? It seems to me that one-way streets are no safer than two-way. Entering a one-way street the wrong way is as easy as driving on the wrong side of a two-way street. And I think two-way streets are safer for pedestrians trying to cross the road - the cars always come from the same direction.
One way streets work well if you have a tight grid system, like in most downtown areas. But a vast majority of the streets are not laid out this way. They are essentially on a much larger grid/web, and making them one-way would make many trips significantly longer.
For instance, here in Connecticut, there might only be a single two-lane road connecting two points on the map. If you made that road one-way and I wanted to go the other way, I might have to drive 2 miles to the next roughly parallel road. Then 2 miles back at the other end. It would be much less efficient.
One-way streets come in fairly late in the history of cities. In early days, traffic patterns were helter-skelter, with people just making for their destination without even much attention paid to sides of street, much less true lanes.
As cities grew denser, traffic control began to emerge. Policemen were used to direct traffic and keep it moving. Various traffic control devices – stop signs, traffic lights, center strips, lane markings – helped to keep traffic (at first horses and carriages, later cars) from interfering with one another.
I don’t know who first instituted one-way streets in this country. Presumably New York City about 1914. (And see this bit of history here.) Conversions caused major disruptions, and I remember reading that many merchants were unhappy because some traffic would no longer automatically flow past their stores (although in the end many supported them because parking became easier – once you got in the right direction). But note that even in NYC major (and wider) east-west streets remain two way.
The reason for this is that one way streets are useful tools for keeping traffic flowing but are inconvenient for almost all other purposes. They have no real reason to be except in dense high-traffic downtowns.
Nearly all of the one-way streets in Los Angeles are in the Downtown area where there is a very tight grid. And people in L.A. are usually baffled by their existence when they encounter them. There are even intersections in Downtown L.A. where you can’t turn right on a red. I’ve seen that law broken a lot out of sheer ignorance.
But the city is too spread out to have one-way streets in any other part, with the exception of the occasional suburban street that is extremely narrow.
That is to say, I assume, that a pedestrian can never choose wrong on a two-way road; traffic potentially comes from both directions. 
In some one-street towns, the main street is more like every-which way. There’s no traffic to speak of, so pedestrians or small vehicles (4-wheelers, for example) criss-cross Main St. with no problem.
What is a street, but the paved space between buildings? (As opposed to a road, which connects population centers.)
Because no one has come up with an idea for a three way street.
:o [sup]You meant as opposed to one-way streets. Nevermind[/sup]
Well, at least some light was shed on my topic; although I noticed quite a few of you only responded to the opening question and didn’t bother to read the rest of the post, i.e., the part that said I was talking about cities! (Where statistically, the vast majority of us live. :smack: Not outlying surburban or rural areas where the traffic flow is so minimal, you actually notice it when a car goes by.) No one commented on the insanely complex patterns when two two-way streets intersect w/o benefit of a cloverleaf… It’s something to behold, and a real nightmare for pedestrians.
I take issue with this. I do not think the vast majority of people live in cities as apposed to the suburbs.
That’s because an intersection of two 2-way streets is not complicated at all. I don’t really see the problem you’re talking about.
[nitpick]
NO!
(Newtonian) Momentum = mas x velocity.
mass x velocity[sup]2[/sup]/2 => kinetic energy.
[/nitpick]
I have nothing to add to the OP, apart from pointing out that when the denser parts of most cities around here were drawn up (10th - 19th century) , there was very little incentive for one-way streets…
Well, some one way streets is a useful thing, but if all the streets were one way, eventually all the cars would be piled up at the ends, and everyone would have to walk.
Tris
One reason I like street crossings downtown in some European cities is the large letters on the pavement before the crosswalk saying “L O O K L E F T” or “L O O K R I G H T”, telling you which way the traffic is coming from.
I agree. Audiocarp, can you give an example of what you mean by “insanely complex”?
Perhaps you mean that it can be difficult to make a left turn at times, because of the oncoming traffic. When that gets bad enough, they change the traffic light from a simple green/yellow/red, and add a green for “left turns only”.
If that’s not enough, they build a cloverleaf or jughandle. What’s the big deal?
What we’ve got here is a failure to communicate: Keeve, did you see that I wrote that there is NO cloverleaf! Have you ever been in “downtown” Newark and noticed there is no room for that? 
The other fine point people seem to miss is that I’m not asking why 2-way streets evolved, I’m asking: Why the fuck we have them NOW in cities? And why, fer crissake, we let them intersect with other 2-ways? Just think how much simpler the intersection would be with just one-ways: You only have two choices: Straight ahead or turn into the intersecting street WITH the flow of traffic; no need to cross opposing lane(s). With a 2-way, each car can go in three directions, which is madness when both streets are busy. (Realize that traffic in NYC is so heavy in some places we’re perpetually in violation of EPA air quality regulations.) And traffic in BOTH directions on the intersecting street has to stop and wait for the incoming traffic to pass, whereas if they were separated (as on an interstate), only one direction would have to stop. 
OK Popup, so I mixed up my HS physics :smack: and confused kinetic energy and momentum; but, which one is more relevant? And Gazpacho, what is your basis for thinking the vast majority of Americans don’t live in a city? (A city, in my mind, being a town with a pop. of 50,000 or more.)
Yes, I’ve been in Newark and I emphatically agree with Audiocarp on that.
On the other hand, I’ve been in Newark, and they DO have one-way streets.
I think our point of disagreement is that Audiocarp has a much lower tolerance for two-way streets than most other people. We all seem to agree that when streets are relatively traffic-free, two-ways are much more convenient. We also agree that when traffic gets very heavy, two-way streets are totally stupid. I think the only point we disagree on is where we place the cutoff point between them.
Dear Tris,
I must explain the concept of circles to you one day
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- One-way streets can use less real estate, but they’re more of a bother to use. In some places I have been in St Louis, for all the side streets in about a 10 x 10 block grid, all the east-west streets run one way/the same direction, and all the north-south streets run one way/all the same direction. It sucks. If you miss a turn, you end up driving practically into the next f#%@ing county to turn around. And sometimes when you do reach a major street, it too is divided, so you’re still stuck going somewhere you didn’t want to, just to find someplace to turn around. And you can rarely cheat and back up, because the side streets are three (rather narrow) lanes wide, with parking on both sides, that is always full.
Ugh.
Urban sprawl, please. - DougC
- One-way streets can use less real estate, but they’re more of a bother to use. In some places I have been in St Louis, for all the side streets in about a 10 x 10 block grid, all the east-west streets run one way/the same direction, and all the north-south streets run one way/all the same direction. It sucks. If you miss a turn, you end up driving practically into the next f#%@ing county to turn around. And sometimes when you do reach a major street, it too is divided, so you’re still stuck going somewhere you didn’t want to, just to find someplace to turn around. And you can rarely cheat and back up, because the side streets are three (rather narrow) lanes wide, with parking on both sides, that is always full.
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