Favorite intersection type?

[kurumi]

Any intersection the good old Kurumi's Me and the Roads wouldn't allow to build .

It was/is pretty restrictive. Code needed to be able to render the intersection and sign assembly.

[peterj920]

I do like the Echelon Intersection concept.  Basically it splits into 2 one way intersections by having one high intersection and one low intersection. 

[20160805]

Sorry to grave dig, but here's a cool design I found:

http://www.efficient-environmental.com/transportation-sustainability-a-free-flow-intersection/

Advantages are that traffic on both roadways can flow relatively smoothly and you don't need an excessive amount of ROW.

What does everyone think?

[roadfro]

Sorry to grave dig, but here's a cool design I found:

http://www.efficient-environmental.com/transportation-sustainability-a-free-flow-intersection/

Advantages are that traffic on both roadways can flow relatively smoothly and you don't need an excessive amount of ROW.

What does everyone think?

The concept is interesting, but I don't know that it would work from a practical design standpoint. I don't think the design depicts nearly enough room for the rise/fall of the ramps and doesn't seem like it has appropriate turning radii for larger vehicles.

[jakeroot]

Sorry to grave dig, but here's a cool design I found:
...
What does everyone think?

I'll be even shorter than roadfro: not practical nor realistic. Cartoonish. The design has no basis in reality.

[kurumi]

Sorry to grave dig, but here's a cool design I found:

http://www.efficient-environmental.com/transportation-sustainability-a-free-flow-intersection/

Advantages are that traffic on both roadways can flow relatively smoothly and you don't need an excessive amount of ROW.

What does everyone think?

My 2 cents: the rendering looks not to scale. Real construction would need a lot more ROW for the 4 interior ramps (spitballing: 5% grade, 20 ft elevation change ==> opposing roadways are 400 feet apart, minimum. A real engineer could provide more accurate numbers.) There are also significant weaving problems at the ramps; this intersection would be free-flowing only in the same way that cloverleaf interchanges are free-flowing: only at low traffic volumes.

[cl94]

Maybe if they swapped the lights to flashing yellow arrows, they wouldn't even need a protected turn phase, outside of rush hour. Lag the flashing yellow arrows with a long phase for Alum Creek, only swap to green arrow if the backup exceeds the storage space.

You'd still need a protected phase for right turns. Imagine getting stuck behind a school bus or another vehicle that doesn't make rights on red.

[jakeroot]

Maybe if they swapped the lights to flashing yellow arrows, they wouldn't even need a protected turn phase, outside of rush hour. Lag the flashing yellow arrows with a long phase for Alum Creek, only swap to green arrow if the backup exceeds the storage space.

You'd still need a protected phase for right turns. Imagine getting stuck behind a school bus or another vehicle that doesn't make rights on red.

The right turn lanes could trip the protected turn as well (after a minimum amount of time, of course).

School buses don't turn on red?

[tradephoric]

The street view even shows independent operation. This is from August (I'm surprised you didn't notice this, trade):

Maybe if they swapped the lights to flashing yellow arrows, they wouldn't even need a protected turn phase, outside of rush hour. Lag the flashing yellow arrows with a long phase for Alum Creek, only swap to green arrow if the backup exceeds the storage space.

It does look like they run independently.  The reason why I believed they didn't run independent is because I only saw one signal cabinet on streetview.  I'd be curious to see inside that cabinet and I wonder if they have two signal controllers inside that cabinet. 

In regards to the FYA, a lot of agencies wouldn't allow permissive lefts when drivers have to cross 3-lane of opposing through traffic (even during off-peak hours).  I don't think it's specifically banned in the MUTCD, but that's how a lot of agencies would want to run the show.  Similar to how many agencies refuse to allow dual permissive left-turns.  I know that example is a sticky one for you, and I didn't mention it to raise your blood pressure, but there are always these agency specific rules that are going to be followed.

[jakeroot]

The street view even shows independent operation. This is from August (I'm surprised you didn't notice this, trade):

Maybe if they swapped the lights to flashing yellow arrows, they wouldn't even need a protected turn phase, outside of rush hour. Lag the flashing yellow arrows with a long phase for Alum Creek, only swap to green arrow if the backup exceeds the storage space.

It does look like they run independently.  The reason why I believed they didn't run independent is because I only saw one signal cabinet on streetview.  I'd be curious to see inside that cabinet and I wonder if they have two signal controllers inside that cabinet. 

In regards to the FYA, a lot of agencies wouldn't allow permissive lefts when drivers have to cross 3-lane of opposing through traffic (even during off-peak hours).  I don't think it's specifically banned in the MUTCD, but that's how a lot of agencies would want to run the show.  Similar to how many agencies refuse to allow dual permissive left-turns.  I know that example is a sticky one for you, and I didn't mention it to raise your blood pressure, but there are always these agency specific rules that are going to be followed.

Only raises my blood pressure when people suggest that both (crossing 3+ lanes and dual left yields) are bad ideas because they think they're bad ideas. The vast majority of studies that I've read consider both to be perfectly acceptable phasing (when constructed properly). Most agencies seem to be afraid of them, hence why so many outright ban both (though I've discovered that here in Washington, where the DOT bans both, individual cities are free to do as they choose; the ones that use permissive across 3+ lanes or dual left yields seem to really like them).

[6a]

Maybe if they swapped the lights to flashing yellow arrows, they wouldn't even need a protected turn phase, outside of rush hour. Lag the flashing yellow arrows with a long phase for Alum Creek, only swap to green arrow if the backup exceeds the storage space.

You'd still need a protected phase for right turns. Imagine getting stuck behind a school bus or another vehicle that doesn't make rights on red.

The right turn lanes could trip the protected turn as well (after a minimum amount of time, of course).

School buses don't turn on red?

Yeah, thinking about it more, westbound Groveport traffic does back up at times. Plus, Ohio loves its "except curb lane" no turn on red signs.

[tradephoric]

Only raises my blood pressure when people suggest that both (crossing 3+ lanes and dual left yields) are bad ideas because they think they're bad ideas. The vast majority of studies that I've read consider both to be perfectly acceptable phasing (when constructed properly). Most agencies seem to be afraid of them, hence why so many outright ban both (though I've discovered that here in Washington, where the DOT bans both, individual cities are free to do as they choose; the ones that use permissive across 3+ lanes or dual left yields seem to really like them).

I can't fault an agency for wanting to ban permissive left turns in certain scenarios.  I've never read a study that concluded permissive left turns are safer than protected left turns.  You could argue the agency is being too conservative but they aren't being less safe.

[cl94]

Maybe if they swapped the lights to flashing yellow arrows, they wouldn't even need a protected turn phase, outside of rush hour. Lag the flashing yellow arrows with a long phase for Alum Creek, only swap to green arrow if the backup exceeds the storage space.

You'd still need a protected phase for right turns. Imagine getting stuck behind a school bus or another vehicle that doesn't make rights on red.

The right turn lanes could trip the protected turn as well (after a minimum amount of time, of course).

School buses don't turn on red?

School buses and hazmats can't turn on red.

As far as permissive turns across 3+ lanes, you generally won't find that in eastern or midwestern states. You just won't. I can only think of a handful of permissives across 3+ lanes.

[jakeroot]

I can't fault an agency for wanting to ban permissive left turns in certain scenarios.  I've never read a study that concluded permissive left turns are safer than protected left turns.  You could argue the agency is being too conservative but they aren't being less safe.

The studies that I've seen conclude that it isn't any worse with three or more oncoming lanes. Of course, they could eliminate the permissive phase altogether, but if long lines are common at the turn, that can increase driver frustration, particularly when there's no oncoming traffic (and the protected turn was leading, for example).

School buses and hazmats can't turn on red.

Is that a federal law? It isn't followed around here. Buses turn on red all the time (no idea about hazmats though).

As far as permissive turns across 3+ lanes, you generally won't find that in eastern or midwestern states. You just won't. I can only think of a handful of permissives across 3+ lanes.

Very much an agency-by-agency thing. I seem to recall Wisconsin having several, but I could be wrong.

[cl94]

School buses and hazmats can't turn on red.

Is that a federal law? It isn't followed around here. Buses turn on red all the time (no idea about hazmats though).

Depends on the state. Many states in the east forbid it and require school buses to have a sticker saying they do not turn on red, New York being one. City buses are often forbidden as well. Can't remember the Ohio law, but I think they're one where you can't turn on red. Don't know about hazmats, but they typically have a sticker saying they won't turn on red as well.

Even if the law allows it, many school bus operators forbid turns on red.

[DaBigE]

As far as permissive turns across 3+ lanes, you generally won't find that in eastern or midwestern states. You just won't. I can only think of a handful of permissives across 3+ lanes.

Very much an agency-by-agency thing. I seem to recall Wisconsin having several, but I could be wrong.

Madison has a few for sure (especially along University Ave, west of the UW Campus). Definitely depends on the agency. While WisDOT's signal design manual doesn't explicitly forbid permissive phasing for turns crossing 3+ lanes (it does recommend against it), I can't think of any state installations that employ permissive left turn phasing in that situation.

[CNGL-Leudimin]

That was an actual thing. And the light now turns green.

[JMAN_WiS&S]

I can't fault an agency for wanting to ban permissive left turns in certain scenarios.  I've never read a study that concluded permissive left turns are safer than protected left turns.  You could argue the agency is being too conservative but they aren't being less safe.

The studies that I've seen conclude that it isn't any worse with three or more oncoming lanes. Of course, they could eliminate the permissive phase altogether, but if long lines are common at the turn, that can increase driver frustration, particularly when there's no oncoming traffic (and the protected turn was leading, for example).

School buses and hazmats can't turn on red.

Is that a federal law? It isn't followed around here. Buses turn on red all the time (no idea about hazmats though).

As far as permissive turns across 3+ lanes, you generally won't find that in eastern or midwestern states. You just won't. I can only think of a handful of permissives across 3+ lanes.

Very much an agency-by-agency thing. I seem to recall Wisconsin having several, but I could be wrong.

Eau Claire Wisconsin has a dual turn FYA across 2 35mph thru lanes, and now we also have 2 intersections with one approach having dual turn lanes seeing a FYA to cross 3 45mph thru+ a right turn lane. Both of these 45mph intersections operate protected only/protected/permissive during different peak traffic periods.