4-way STOP v. Roundabout efficiency - by the Mythbusters

[tradephoric]

 

I went thru this intersection/roundabout recently. And as luck would have it, the aerial photo shows the older configuration, and GSV shows the newer configuration.

This is Spring Valley Road, which goes from US 322 to US 202 in the Concordville, PA area.

The old intersection, which was a 4 way stop: http://goo.gl/maps/VlFS8

The new roundabout...with a 4 way stop! http://goo.gl/maps/EQv15

So i could place a flower planter in the middle of an intersection and call it a roundabout?

[vdeane]

If Quebec can build this thing... http://goo.gl/maps/ofGLZ

[1995hoo]

If Quebec can build this thing... http://goo.gl/maps/ofGLZ

Post that in the thread about keeping traffic moving at a red light!

[NE2]

So i could place a flower planter in the middle of an intersection and call it a roundabout?

It it's marked as one, yes.

[mass_citizen]

http://www.lowellsun.com/news/ci_24099795/pepperell-board-votes-against-pursuing-rotary?source=rss_emailed

Here is an example of a small town political board voting against a roundabout without any traffic engineering study being done. One possible reason is that they refer to it as a "rotary" which in Massachusetts is different from a "roundabout" (mostly in size and speed of travel). "Rotary" has a somewhat negative connotation in Mass due to some notorious ones that were locations of frequent traffic jams. I think the intent in this case was to use a "roundabout" to replace the multi-way (not all way) stop.

The intersection in question is here:   https://maps.google.com/maps?hl=en&ll=42.666829,-71.573369&spn=0.001803,0.004013&t=h&z=18

My opinion is that if they did do a true traffic study the engineers would find that a roundabout would be more efficient than the current configuration.

[spooky]

http://www.lowellsun.com/news/ci_24099795/pepperell-board-votes-against-pursuing-rotary?source=rss_emailed

Here is an example of a small town political board voting against a roundabout without any traffic engineering study being done. One possible reason is that they refer to it as a "rotary" which in Massachusetts is different from a "roundabout" (mostly in size and speed of travel). "Rotary" has a somewhat negative connotation in Mass due to some notorious ones that were locations of frequent traffic jams. I think the intent in this case was to use a "roundabout" to replace the multi-way (not all way) stop.

The intersection in question is here:   https://maps.google.com/maps?hl=en&ll=42.666829,-71.573369&spn=0.001803,0.004013&t=h&z=18

My opinion is that if they did do a true traffic study the engineers would find that a roundabout would be more efficient than the current configuration.

From looking at the satellite imagery, I think you can pretty quickly discount a roundabout without doing a traffic study, especially if they intend to maintain parking.

[english si]

If Quebec can build this thing... http://goo.gl/maps/ofGLZ

That's massive. Bricks? Deflection? Pah, all you need is some paint and some signs.

From looking at the satellite imagery, I think you can pretty quickly discount a roundabout without doing a traffic study, especially if they intend to maintain parking.

As has been shown, small roundabouts exist. And there's tons of room there, even maintaining the parking.

[Brandon]

That's massive. Bricks? Deflection? Pah, all you need is some paint and some signs.

Yeah...  I can just see how that'll work here, around Chicago.  Countdown until the first T-bone accident in 5..4..3..2..1...

[spooky]

From looking at the satellite imagery, I think you can pretty quickly discount a roundabout without doing a traffic study, especially if they intend to maintain parking.

As has been shown, small roundabouts exist. And there's tons of room there, even maintaining the parking.

I think I can see what you're suggesting, but I don't see how you bring Railroad St into it.

[jeffandnicole]

If Quebec can build this thing... http://goo.gl/maps/ofGLZ

That's massive. Bricks? Deflection? Pah, all you need is some paint and some signs.

From looking at the satellite imagery, I think you can pretty quickly discount a roundabout without doing a traffic study, especially if they intend to maintain parking.

As has been shown, small roundabouts exist. And there's tons of room there, even maintaining the parking.

Looking at the very straight oil line thru the lanes, I don't think traffic is curving to go around the paint in the middle of the roadway.

[Duke87]

Looking at the very straight oil line thru the lanes, I don't think traffic is curving to go around the paint in the middle of the roadway.

More to the point, if I were going to make a right turn there, I'd be driving across the dot, not around it.


Nonetheless, this setup in theory should work... if everyone yields to each other properly. That's not something you can generally trust American drivers to do, especially when the yield is only implied by pavement marking rather than explicitly stated with a sign. Americans are thickheadded, we need things spelled out for us.

[Indyroads]

If Quebec can build this thing... http://goo.gl/maps/ofGLZ

That's massive. Bricks? Deflection? Pah, all you need is some paint and some signs.

From looking at the satellite imagery, I think you can pretty quickly discount a roundabout without doing a traffic study, especially if they intend to maintain parking.

As has been shown, small roundabouts exist. And there's tons of room there, even maintaining the parking.

Looking at the very straight oil line thru the lanes, I don't think traffic is curving to go around the paint in the middle of the roadway.

this is a great candidate for a worst roundabouts around the world thread. Why not just be like those quirky US blokes and put in the ole' 4 way stop gov-na.

[1995hoo]

If Quebec can build this thing... http://goo.gl/maps/ofGLZ

That's massive. Bricks? Deflection? Pah, all you need is some paint and some signs.

From looking at the satellite imagery, I think you can pretty quickly discount a roundabout without doing a traffic study, especially if they intend to maintain parking.

As has been shown, small roundabouts exist. And there's tons of room there, even maintaining the parking.

Looking at the very straight oil line thru the lanes, I don't think traffic is curving to go around the paint in the middle of the roadway.

this is a great candidate for a worst roundabouts around the world thread. Why not just be like those quirky US blokes and put in the ole' 4 way stop gov-na.

What for? A mini-roundabout means you yield–you only have to stop if there's someone already there to whom you are required to yield. I like that a lot better than the silly American idea that you might have to stop sometime, so you should be required to stop every time Just In Case. Giving way properly is more important than the dot painted on the asphalt.

[Brandon]

If Quebec can build this thing... http://goo.gl/maps/ofGLZ

That's massive. Bricks? Deflection? Pah, all you need is some paint and some signs.

From looking at the satellite imagery, I think you can pretty quickly discount a roundabout without doing a traffic study, especially if they intend to maintain parking.

As has been shown, small roundabouts exist. And there's tons of room there, even maintaining the parking.

Looking at the very straight oil line thru the lanes, I don't think traffic is curving to go around the paint in the middle of the roadway.

this is a great candidate for a worst roundabouts around the world thread. Why not just be like those quirky US blokes and put in the ole' 4 way stop gov-na.

What for? A mini-roundabout means you yield–you only have to stop if there's someone already there to whom you are required to yield. I like that a lot better than the silly American idea that you might have to stop sometime, so you should be required to stop every time Just In Case. Giving way properly is more important than the dot painted on the asphalt.

The problem in this particular example is that the sight lines are very poor.  I would've recommended a four-way stop here if both roads have a near-equal amount of traffic due to the very poor sight lines.  If the hedges and stone walls were not here, I'd agree that a mini-roundabout is better, but they are, and a four-way stop might be safer.  There is no way you can adequately see vehicles, bicycles, or pedestrians at this intersection.

[english si]

I think I can see what you're suggesting, but I don't see how you bring Railroad St into it.

I thought I'd keep it simple, but you can do a double mini-roundabout if you want to include it.

Looking at the very straight oil line thru the lanes, I don't think traffic is curving to go around the paint in the middle of the roadway.

Yes, it isn't, but mini roundabouts are more a short-hand way of saying "Give Way to Traffic from Right"

this is a great candidate for a worst roundabouts around the world thread. Why not just be like those quirky US blokes and put in the ole' 4 way stop gov-na.

Stop signs need special authorisation in the UK, though the visibility here would justify it. However traffic would slow to almost a rolling stop in order to make sure they were giving way to traffic from the right (and right turning traffic from straight on).

4-Way stop is worse as 1) you have to look in both directions (left and right) before entering the junction due to the 'who comes first' priority rather than the 'to the right' priority.
2) you have to stop.

What for? A mini-roundabout means you yield–you only have to stop if there's someone already there to whom you are required to yield. I like that a lot better than the silly American idea that you might have to stop sometime, so you should be required to stop every time Just In Case. Giving way properly is more important than the dot painted on the asphalt.

Like

The problem in this particular example is that the sight lines are very poor.  I would've recommended a four-way stop here if both roads have a near-equal amount of traffic due to the very poor sight lines.  If the hedges and stone walls were not here, I'd agree that a mini-roundabout is better, but they are, and a four-way stop might be safer.  There is no way you can adequately see vehicles, bicycles, or pedestrians at this intersection.

Traffic speeds would be very low - there's no way that stopping would make it safer as even if stopped, you'd still have the same visibility problems.

And the stupid unclear priority rules (and uniqueness of a four-way stop in the UK) would add confusion, which will decrease safety.

Not to mention the boy-who-cried-wolf syndrome that means that the use of STOP over GIVE WAY is very controlled in the UK.

Here's the junction on Street View.

[Brandon]

4-Way stop is worse as 1) you have to look in both directions (left and right) before entering the junction due to the 'who comes first' priority rather than the 'to the right' priority.

And the stupid unclear priority rules (and uniqueness of a four-way stop in the UK) would add confusion, which will decrease safety.

Not to mention the boy-who-cried-wolf syndrome that means that the use of STOP over GIVE WAY is very controlled in the UK.

Here's the junction on Street View.

Even though some idiots don't seem to understand this, there are priority rules for an all-way stop.

1. First-come, first serve.  If you are there first, you go first.  If you are there second, you wait for the first person to go.  (Bolded, italicized, and underlined as this is what you do, don't wave someone else!)
2. Priority to the right.  If you arrive at the same time as another driver, the driver to the right goes first, be it you or the other driver.  (Who says we don't have priority to the right in the US and Canada.  )
3. Straight then left.  Straight movements are supposed to go first, then the left (right in RHD countries) goes behind the straight movement.

[agentsteel53]

Even though some idiots don't seem to understand this, there are priority rules for an all-way stop.

1. First-come, first serve.  If you are there first, you go first.  If you are there second, you wait for the first person to go.  (Bolded, italicized, and underlined as this is what you do, don't wave someone else!)
2. Priority to the right.  If you arrive at the same time as another driver, the driver to the right goes first, be it you or the other driver.  (Who says we don't have priority to the right in the US and Canada.  )
3. Straight then left.  Straight movements are supposed to go first, then the left (right in RHD countries) goes behind the straight movement.

the problem with this is that 1 contradicts 2/3.

if I arrive a split second before someone to my right does, then I have right of way by rule 1, and he has right of way by rule 2, all within the margin of observer error.

[vdeane]

Hence the order.  In the US/Canada, it's 1, 2, 3.  In Europe, it's 2 no matter what.

Yes, it isn't, but mini roundabouts are more a short-hand way of saying "Give Way to Traffic from Right"

Given that this is Europe, wouldn't a four-way yield mean the same thing?

[Mr_Northside]

if I arrive a split second before someone to my right does, then I have right of way by rule 1, and he has right of way by rule 2, all within the margin of observer error.

I can't really think of a time when the notion of "Priority to the Right" has noticeably come into a play at any multi-way stop sign intersection I've navigated. 
It usually comes down to the perception of who got to the point-of-stop first, even by that "split second".  If two cars arrive at almost the same time - so close it might as well be the same time - rather than anyone defaulting to the "Priority to the Right", it's usually an exercise in social behavior where someone either aggressively feels that they were there first and goes before the other person (though usually in a way where there won't be a collision), or a driver who simply waves (or flashes) the other motorist on first to avoid any conflict. 

Maybe it's different some places, but I've found that unless someone were to be at the intersection to irrefutably prove to motorists that cars got there at literally the same time (triggering rules #2 & 3), someone always got there first.

[english si]

Given that this is Europe, wouldn't a four-way yield mean the same thing?

Not in the UK, as there's no default priority to the left (or right) as there is prioritie-a-droit in France, etc. Plus roundabouts in France are prioritie-a-gauche (just as UK ones are give-way-to-right), so a 4-way yield would do the opposite.

[maplestar]

If Quebec can build this thing... http://goo.gl/maps/ofGLZ

Wow, that's only about half a mile from the house of my mother's aunt! I haven't been there in several years, though.

[agentsteel53]

it's usually an exercise in social behavior where someone either aggressively feels that they were there first and goes before the other person (though usually in a way where there won't be a collision), or a driver who simply waves (or flashes) the other motorist on first to avoid any conflict. 

if I feel like a situation like this is impending, I purposely slow down enough to have the other driver clearly get there ahead of me.

it's effective about 85% of the time, which is pretty good given that most people around the residential neighborhood in which I most often encounter four-way stops (basically, "between my work and Home Depot") are morons.

[J N Winkler]

Given that this is Europe, wouldn't a four-way yield mean the same thing?

No--mini-roundabouts are not the same as stop or yield control (regardless of priority rule) because drivers are required to do whatever is reasonably possible to avoid driving over the painted dot in the middle of the intersection.  The dot is there to force traffic entering the intersection to circulate as if it is in a roundabout, and this overrides priority of straight-ahead traffic over turning traffic, priority of traffic approaching from left or right (English Si is correct to say that the UK has no handed-priority rule like the US and continental Europe--this is one thing the British just don't do, like curve advisory speeds), and priority of earlier-arriving traffic, all of which cause problems at US four-way stops.

There are very good reasons four-way stops (or four-way yields in countries where stop control is reserved for unusual visibility limitation) are not used even in countries that don't use mini-roundabouts.

[andy]

I always felt the yield right rule was a result of the practical implications of the "disputed" portion of the intersection.  If the left driver eases forward, the right driver either yields (stays put) or claims the intersection (proceedes).  In the second case, the left driver is then required to slow or wait until the right driver, who gets to the disputed quadrant first, clears.  As long as no one jack-rabbits, it works quite effectively.

[vdeane]

Given that this is Europe, wouldn't a four-way yield mean the same thing?

No--mini-roundabouts are not the same as stop or yield control (regardless of priority rule) because drivers are required to do whatever is reasonably possible to avoid driving over the painted dot in the middle of the intersection.  The dot is there to force traffic entering the intersection to circulate as if it is in a roundabout, and this overrides priority of straight-ahead traffic over turning traffic, priority of traffic approaching from left or right (English Si is correct to say that the UK has no handed-priority rule like the US and continental Europe--this is one thing the British just don't do, like curve advisory speeds), and priority of earlier-arriving traffic, all of which cause problems at US four-way stops.

There are very good reasons four-way stops (or four-way yields in countries where stop control is reserved for unusual visibility limitation) are not used even in countries that don't use mini-roundabouts.

Well, that means we won't see mini-roundabouts in the US!  I don't think it's even physically possible for American cars to avoid the dot.