At some point in the near future, the people of Prince William County, Virginia will bear witness to a great revolution in traffic engineering. The VDOT plans to turn the current intersection between the Prince William Parkway and Clover Hill Road into a Bowtie Intersection and it is a thing of beauty
(https://i.imgur.com/Z3v26BG.png)
2 roundabouts will be installed on Clover Hill on opposite sides of the Parkway. All Left Turns at the main intersection will be prohibited and instead drivers will use the roundabouts to make a u turn to complete their movements. It's essentially an at-grade version of a dogbone interchange. It means the main intersection can use a simple 2 phase signal. It improves traffic capacity and safety.
There are many so-called innovative intersections that do the same thing such as the RCUT, the Michigan Left, the Jughandle, and the Continuous Flow Intersection, but those require a massive amount of right-of-way. This does not, in fact, as you can see, by getting rid of the need for left turn lanes, it takes up less space than a conventional intersection. I hope that this is the beginning of a glorious revolution.
How does a median U-turn require so much ROW? There already appears to be a wide enough median.
Quote from: 1 on November 25, 2020, 09:53:22 AM
How does a median U-turn require so much ROW? There already appears to be a wide enough median.
Maybe not this particular example, but many arterials that could benefit from eliminating left turns don't have enough space for a Michigan left that can accommodate big trucks and buses, and almost all of those require signalization. Also, by leaving the median in place, it allows space for future widenings.
Quote from: kernals12 on November 25, 2020, 09:50:40 AM
.... I hope that this is the beginning of a glorious revolution.
That would be more likely if this project were in the Williamsburg area.... :hmm:
Quote from: 1 on November 25, 2020, 09:53:22 AM
How does a median U-turn require so much ROW? There already appears to be a wide enough median.
This is a Street View of that intersection now, BTW.
https://goo.gl/maps/ttgKcFdH3Fp2JBFo7
Anyone care to explain the benefits of this versus a regular roundabout or even traffic light? It has to be more expensive, and there's no way it decreases travel time with all of that extra driving.
The other good thing about it is it should be relatively simple to convert into a dog bone interchange. You'd just need grade separate the main intersection and then build entrance and exit ramps to those roundabouts. And turning VA 234 into a freeway between I-66 and Brentsville Road is in the Long Term Plans.
I think that it would be practical to build these types of intersections on MA 9 and especially MA 2.
Quote from: thspfc on November 25, 2020, 10:02:46 AM
Anyone care to explain the benefits of this versus a regular roundabout or even traffic light? It has to be more expensive, and there's no way it decreases travel time with all of that extra driving.
It's a 2-phase signal. If there are left turn lanes, it's a 4-phase signal.
Quote from: thspfc on November 25, 2020, 10:02:46 AM
Anyone care to explain the benefits of this versus a regular roundabout or even traffic light? It has to be more expensive, and there's no way it decreases travel time with all of that extra driving.
It gets rid of left turn phases at the main intersection so more green time can be given to people going straight. And while people making left turns will have to drive further, they will spend less time waiting at red lights.
And roundabouts don't work when traffic going in one direction is much greater than traffic going in another.
Quote from: kernals12 on November 25, 2020, 10:07:42 AM
Quote from: thspfc on November 25, 2020, 10:02:46 AM
Anyone care to explain the benefits of this versus a regular roundabout or even traffic light? It has to be more expensive, and there's no way it decreases travel time with all of that extra driving.
It gets rid of left turn phases at the main intersection so more green time can be given to people going straight. And while people making left turns will have to drive further, they will spend less time waiting at red lights.
And roundabouts don't work when traffic going in one direction is much greater than traffic going in another.
So does that decrease travel time overall then? I suppose it depends on how long those light phases were.
Quote from: thspfc on November 25, 2020, 11:22:05 AM
Quote from: kernals12 on November 25, 2020, 10:07:42 AM
Quote from: thspfc on November 25, 2020, 10:02:46 AM
Anyone care to explain the benefits of this versus a regular roundabout or even traffic light? It has to be more expensive, and there's no way it decreases travel time with all of that extra driving.
It gets rid of left turn phases at the main intersection so more green time can be given to people going straight. And while people making left turns will have to drive further, they will spend less time waiting at red lights.
And roundabouts don't work when traffic going in one direction is much greater than traffic going in another.
So does that decrease travel time overall then? I suppose it depends on how long those light phases were.
I'm guessing the number of people going straight on the Prince William Parkway outnumber all other traffic movements at that intersection, so on average, travel times would decrease. And I think the people who are going left will find it
feels faster since they aren't waiting at traffic lights.
Quote from: 1995hoo on November 25, 2020, 09:57:31 AM
Quote from: 1 on November 25, 2020, 09:53:22 AM
How does a median U-turn require so much ROW? There already appears to be a wide enough median.
This is a Street View of that intersection now, BTW.
https://goo.gl/maps/ttgKcFdH3Fp2JBFo7
I also want to point out that, in this particular instance, the roundabouts were specifically designed with airport truck traffic in mind. Trucks are less able to navigate median U-turns unless the median is of sufficient width.
Quote from: kernals12 on November 25, 2020, 11:30:22 AM
Quote from: thspfc on November 25, 2020, 11:22:05 AM
Quote from: kernals12 on November 25, 2020, 10:07:42 AM
Quote from: thspfc on November 25, 2020, 10:02:46 AM
Anyone care to explain the benefits of this versus a regular roundabout or even traffic light? It has to be more expensive, and there's no way it decreases travel time with all of that extra driving.
It gets rid of left turn phases at the main intersection so more green time can be given to people going straight. And while people making left turns will have to drive further, they will spend less time waiting at red lights.
And roundabouts don't work when traffic going in one direction is much greater than traffic going in another.
So does that decrease travel time overall then? I suppose it depends on how long those light phases were.
I'm guessing the number of people going straight on the Prince William Parkway outnumber all other traffic movements at that intersection, so on average, travel times would decrease. And I think the people who are going left will find it feels faster since they aren't waiting at traffic lights.
That makes sense.
It will cut down on travel time...if used properly.
These aren't conventional roundabouts. Traffic going straight will probably fly thru the roundabout. The traffic within the roundabout may have a tendency to yield. If you have two cars waiting, then you start jamming up the roundabout.
Why even have a roundabout anyway? What are the chances of a car making a u-turn on Clover approaching Prince William? If a motorist on Clover really needed to make a u-turn, they can just do so after going thru the intersection.
Quote from: jeffandnicole on November 25, 2020, 12:28:55 PM
Why even have a roundabout anyway? What are the chances of a car making a u-turn on Clover approaching Prince William? If a motorist on Clover really needed to make a u-turn, they can just do so after going thru the intersection.
I agree that dual teardrops would be better. On the other hand, if nobody will be making those movements, then it really doesn't hurt anything to have the pavement available there, plus it gives snow plows an extra option.
I've thought about something similar here (https://www.google.com/maps/@42.6488314,-71.3047633,16.63z) in Lowell. It's currently a 4-phase signal. There's a rotary interchange to the east, and there's an authorized vehicles only median U-turn to the west that could become public usage. This would make it a 2-phase signal if left turns are banned.
Quote from: 1 on November 25, 2020, 10:07:00 AM
Quote from: thspfc on November 25, 2020, 10:02:46 AM
Anyone care to explain the benefits of this versus a regular roundabout or even traffic light? It has to be more expensive, and there's no way it decreases travel time with all of that extra driving.
It's a 2-phase signal. If there are left turn lanes, it's a 4-phase signal.
The addition of left turn lanes has no bearing on the number of phases. Many large intersections have no protected turn phase.
Quote from: 1 on November 25, 2020, 12:33:58 PM
I've thought about something similar here (https://www.google.com/maps/@42.6488314,-71.3047633,16.63z) in Lowell. It's currently a 4-phase signal. There's a rotary interchange to the east, and there's an authorized vehicles only median U-turn to the west that could become public usage. This would make it a 2-phase signal if left turns are banned.
That median U turn is way too far from the main intersection.
Quote from: kernals12 on November 25, 2020, 12:42:30 PM
Quote from: 1 on November 25, 2020, 12:33:58 PM
I've thought about something similar here (https://www.google.com/maps/@42.6488314,-71.3047633,16.63z) in Lowell. It's currently a 4-phase signal. There's a rotary interchange to the east, and there's an authorized vehicles only median U-turn to the west that could become public usage. This would make it a 2-phase signal if left turns are banned.
That median U turn is way too far from the main intersection.
Also how much is that rotary used? You don't want to send more traffic to use the rotary if it results in the rotary overloading. Which the view here (https://www.google.com/maps/@42.6481076,-71.2997311,3a,75y,142.71h,71.86t/data=!3m6!1e1!3m4!1sVK-AAUWcsmL_u1Sl1N-O1w!2e0!7i13312!8i6656) shows how adding those additional vehicles could be problematic since there's already evidence that the rotary can jam due to the number of vehicles going towards the bridge. Or is that due to traffic backing up across the bridge?
The time has come that we seriously need to start drug-testing engineers.
^^ During my last stint as an Engineer, I has to take a pre-employment drug test.
Quote from: hbelkins on November 25, 2020, 02:02:46 PM
The time has come that we seriously need to start drug-testing engineers.
How is this not at least as good as Michigan lefts?
One change I would make is to add slip lanes for traffic getting onto the parkway. That ensures that people going left don't hit a red light more than once.
Quote from: kernals12 on November 25, 2020, 02:52:54 PM
One change I would make is to add slip lanes for traffic getting onto the parkway. That ensures that people going left don't hit a red light more than once.
Ped/Bike Safety advocates like it this way though.
Quote from: jeffandnicole on November 25, 2020, 03:29:29 PM
Quote from: kernals12 on November 25, 2020, 02:52:54 PM
One change I would make is to add slip lanes for traffic getting onto the parkway. That ensures that people going left don't hit a red light more than once.
Ped/Bike Safety advocates like it this way though.
People walk across this road??
Quote from: kernals12 on November 25, 2020, 03:46:05 PM
People walk across this road??
There are crosswalks that connect to nothing. However, that was
only half (https://goo.gl/maps/5pJzWCKoK1BieKWF7) of what J&N was talking about.
Quote from: kernals12 on November 25, 2020, 03:46:05 PM
Quote from: jeffandnicole on November 25, 2020, 03:29:29 PM
Quote from: kernals12 on November 25, 2020, 02:52:54 PM
One change I would make is to add slip lanes for traffic getting onto the parkway. That ensures that people going left don't hit a red light more than once.
Ped/Bike Safety advocates like it this way though.
People walk across this road??
Maybe not a bunch, but some certainly. Not building infrastructure for them isn't sound practice.
As to the slip lanes: they can be designed to better facilitate pedestrian movements. They are not universally hated. In fact, they can actually reduce crossing distances and provide refuge spots, two important features for pedestrian safety. As well, the crossings at the signal itself are usually safer, as there is no right turning traffic to deal with (and left turns can be protected).
Quote from: jakeroot on November 25, 2020, 06:26:38 PM
Quote from: kernals12 on November 25, 2020, 03:46:05 PM
Quote from: jeffandnicole on November 25, 2020, 03:29:29 PM
Quote from: kernals12 on November 25, 2020, 02:52:54 PM
One change I would make is to add slip lanes for traffic getting onto the parkway. That ensures that people going left don't hit a red light more than once.
Ped/Bike Safety advocates like it this way though.
People walk across this road??
Maybe not a bunch, but some certainly. Not building infrastructure for them isn't sound practice.
As to the slip lanes: they can be designed to better facilitate pedestrian movements. They are not universally hated. In fact, they can actually reduce crossing distances and provide refuge spots, two important features for pedestrian safety. As well, the crossings at the signal itself are usually safer, as there is no right turning traffic to deal with (and left turns can be protected).
This intersection will have no left turns as I explained.
Quote from: kernals12 on November 25, 2020, 06:35:02 PM
Quote from: jakeroot on November 25, 2020, 06:26:38 PM
Quote from: kernals12 on November 25, 2020, 03:46:05 PM
Quote from: jeffandnicole on November 25, 2020, 03:29:29 PM
Quote from: kernals12 on November 25, 2020, 02:52:54 PM
One change I would make is to add slip lanes for traffic getting onto the parkway. That ensures that people going left don't hit a red light more than once.
Ped/Bike Safety advocates like it this way though.
People walk across this road??
Maybe not a bunch, but some certainly. Not building infrastructure for them isn't sound practice.
As to the slip lanes: they can be designed to better facilitate pedestrian movements. They are not universally hated. In fact, they can actually reduce crossing distances and provide refuge spots, two important features for pedestrian safety. As well, the crossings at the signal itself are usually safer, as there is no right turning traffic to deal with (and left turns can be protected).
This intersection will have no left turns as I explained.
I was speaking more generally (and mostly towards
jeffandnicole's comment) about slip lanes and this impression that they may not be compatible with pedestrians and cyclists.
QuoteThere are many so-called innovative intersections that do the same thing such as the RCUT, the Michigan Left, the Jughandle, and the Continuous Flow Intersection, but those require a massive amount of right-of-way.
The first two intersections you mention do
*NOT* require a "massive amount of right-of-way. In fact, many RCUT applications require
less right-of-way than the roundabouts in the bowtie proposal you showed.
Most Michigan Left applications occur with roadways that already have a wide median, so no additional right-of-way needed there either.
As for the bike/ped comments of the latest posts, Strava heat map data suggests that a number of bicyclists do cross 234 at this intersection.
Quote from: jakeroot on November 25, 2020, 07:38:11 PM
Quote from: kernals12 on November 25, 2020, 06:35:02 PM
Quote from: jakeroot on November 25, 2020, 06:26:38 PM
Quote from: kernals12 on November 25, 2020, 03:46:05 PM
Quote from: jeffandnicole on November 25, 2020, 03:29:29 PM
Quote from: kernals12 on November 25, 2020, 02:52:54 PM
One change I would make is to add slip lanes for traffic getting onto the parkway. That ensures that people going left don't hit a red light more than once.
Ped/Bike Safety advocates like it this way though.
People walk across this road??
Maybe not a bunch, but some certainly. Not building infrastructure for them isn't sound practice.
As to the slip lanes: they can be designed to better facilitate pedestrian movements. They are not universally hated. In fact, they can actually reduce crossing distances and provide refuge spots, two important features for pedestrian safety. As well, the crossings at the signal itself are usually safer, as there is no right turning traffic to deal with (and left turns can be protected).
This intersection will have no left turns as I explained.
I was speaking more generally (and mostly towards jeffandnicole's comment) about slip lanes and this impression that they may not be compatible with pedestrians and cyclists.
I didn't say they weren't compatible...I'm just saying that ped/buke people tend to want to stop traffic as much as possible, and even slip lanes are looked upon negatively.
Quote from: kernals12 on November 25, 2020, 06:35:02 PM
Quote from: jakeroot on November 25, 2020, 06:26:38 PM
Quote from: kernals12 on November 25, 2020, 03:46:05 PM
Quote from: jeffandnicole on November 25, 2020, 03:29:29 PM
Quote from: kernals12 on November 25, 2020, 02:52:54 PM
One change I would make is to add slip lanes for traffic getting onto the parkway. That ensures that people going left don't hit a red light more than once.
Ped/Bike Safety advocates like it this way though.
People walk across this road??
Maybe not a bunch, but some certainly. Not building infrastructure for them isn't sound practice.
As to the slip lanes: they can be designed to better facilitate pedestrian movements. They are not universally hated. In fact, they can actually reduce crossing distances and provide refuge spots, two important features for pedestrian safety. As well, the crossings at the signal itself are usually safer, as there is no right turning traffic to deal with (and left turns can be protected).
This intersection will have no left turns as I explained.
You mean no left turns will technically be permitted. People on Clover Hill are still going to turn left at the light regardless of what the signs say.
Quote from: 1995hoo on November 26, 2020, 09:11:15 PM
Quote from: kernals12 on November 25, 2020, 06:35:02 PM
Quote from: jakeroot on November 25, 2020, 06:26:38 PM
Quote from: kernals12 on November 25, 2020, 03:46:05 PM
Quote from: jeffandnicole on November 25, 2020, 03:29:29 PM
Quote from: kernals12 on November 25, 2020, 02:52:54 PM
One change I would make is to add slip lanes for traffic getting onto the parkway. That ensures that people going left don't hit a red light more than once.
Ped/Bike Safety advocates like it this way though.
People walk across this road??
Maybe not a bunch, but some certainly. Not building infrastructure for them isn't sound practice.
As to the slip lanes: they can be designed to better facilitate pedestrian movements. They are not universally hated. In fact, they can actually reduce crossing distances and provide refuge spots, two important features for pedestrian safety. As well, the crossings at the signal itself are usually safer, as there is no right turning traffic to deal with (and left turns can be protected).
This intersection will have no left turns as I explained.
You mean no left turns will technically be permitted. People on Clover Hill are still going to turn left at the light regardless of what the signs say.
They can channelize it such that people can't turn left.
Quote from: kernals12 on November 26, 2020, 09:30:59 PM
They can channelize it such that people can't turn left.
IMO this is a drawback of MUT / bowtie - if both the major and minor road traffic can go straight, there isn't really a possible way to physically prevent left turns (as far as I know). That's unlike RCUT / superstreet, where islands force minor road traffic to turn right.
VDOT's tweet this afternoon made me think of this thread. Same intersection.
https://twitter.com/VaDOTNOVA/status/1363928216734416903
Put some jughandles in and be done with it. :sombrero:
Quote from: NJRoadfan on February 22, 2021, 02:36:48 PM
Put some jughandles in and be done with it. :sombrero:
These are essentially jughandles.
https://www.google.com/maps/@40.4853807,-74.4223007,3a,60.4y,314.88h,79.07t/data=!3m6!1e1!3m4!1sm38QTADzTPvD8hnaX8ltFg!2e0!7i16384!8i8192
Quote from: NE2 on February 22, 2021, 05:08:44 PM
Quote from: NJRoadfan on February 22, 2021, 02:36:48 PM
Put some jughandles in and be done with it. :sombrero:
These are essentially jughandles.
https://www.google.com/maps/@40.4853807,-74.4223007,3a,60.4y,314.88h,79.07t/data=!3m6!1e1!3m4!1sm38QTADzTPvD8hnaX8ltFg!2e0!7i16384!8i8192
I love that the standard Jersey left is basically just every other states' unofficial impatient left turn. Aka, "this left turn signal fucking blows, I'm going right and banging a uey".
Quote from: jakeroot on February 23, 2021, 07:20:54 PM
Quote from: NE2 on February 22, 2021, 05:08:44 PM
Quote from: NJRoadfan on February 22, 2021, 02:36:48 PM
Put some jughandles in and be done with it. :sombrero:
These are essentially jughandles.
https://www.google.com/maps/@40.4853807,-74.4223007,3a,60.4y,314.88h,79.07t/data=!3m6!1e1!3m4!1sm38QTADzTPvD8hnaX8ltFg!2e0!7i16384!8i8192
I love that the standard Jersey left is basically just every other states' unofficial impatient left turn. Aka, "this left turn signal fucking blows, I'm going right and banging a uey".
That sounds more like a Michigan left.
Quote from: kernals12 on February 23, 2021, 07:51:43 PM
Quote from: jakeroot on February 23, 2021, 07:20:54 PM
Quote from: NE2 on February 22, 2021, 05:08:44 PM
Quote from: NJRoadfan on February 22, 2021, 02:36:48 PM
Put some jughandles in and be done with it. :sombrero:
These are essentially jughandles.
https://www.google.com/maps/@40.4853807,-74.4223007,3a,60.4y,314.88h,79.07t/data=!3m6!1e1!3m4!1sm38QTADzTPvD8hnaX8ltFg!2e0!7i16384!8i8192
I love that the standard Jersey left is basically just every other states' unofficial impatient left turn. Aka, "this left turn signal fucking blows, I'm going right and banging a uey".
That sounds more like a Michigan left.
Fundamentally they're very similar: an indirect left.
Quote from: kernals12 on November 25, 2020, 09:50:40 AM
At some point in the near future, the people of Prince William County, Virginia will bear witness to a great revolution in traffic engineering. The VDOT plans to turn the current intersection between the Prince William Parkway and Clover Hill Road into a Bowtie Intersection and it is a thing of beauty
(https://i.imgur.com/Z3v26BG.png)
2 roundabouts will be installed on Clover Hill on opposite sides of the Parkway. All Left Turns at the main intersection will be prohibited and instead drivers will use the roundabouts to make a u turn to complete their movements. It's essentially an at-grade version of a dogbone interchange. It means the main intersection can use a simple 2 phase signal. It improves traffic capacity and safety.
There are many so-called innovative intersections that do the same thing such as the RCUT, the Michigan Left, the Jughandle, and the Continuous Flow Intersection, but those require a massive amount of right-of-way. This does not, in fact, as you can see, by getting rid of the need for left turn lanes, it takes up less space than a conventional intersection. I hope that this is the beginning of a glorious revolution.
Here's a Median U-turn intersection in Michigan with the same median width as Prince William Pkwy. Admittedly I'm a little partial to Median U-turns but i don't see much advantage going with the BowTie intersection in the OP's example.
(https://i.imgur.com/VSZOFO1.png)
https://www.google.com/maps/@42.7520685,-83.2466276,545m/data=!3m1!1e3
Notice those loons. That means traffic going straight on the main road has to stop for those making a u turn. With the bowtie, all movements are done on the minor road so the smooth procession of traffic on the major road is uninterrupted.
Quote from: kernals12 on February 24, 2021, 08:07:56 AM
Notice those loons. That means traffic going straight on the main road has to stop for those making a u turn. With the bowtie, all movements are done on the minor road so the smooth procession of traffic on the major road is uninterrupted.
The U-turn points usually aren't signalized; this one appears to be a rare exception. Usually, if you're on the U-turn ramp, you just merge when you can. (Some median U-turn intersections add a lane for U-turners so that they don't have to wait for a gap in traffic.)
Quote from: kernals12 on February 24, 2021, 08:07:56 AM
Notice those loons. That means traffic going straight on the main road has to stop for those making a u turn. With the bowtie, all movements are done on the minor road so the smooth procession of traffic on the major road is uninterrupted.
The signalized crossovers are coordinated with the main signal so if you get stopped at the crossover you would have gotten stopped at the main signal anyways. The only main-street drivers delayed by the crossover are those wishing to make a right turn onto the side-street (and that's assuming there isn't a "no right turn on red" sign).
kernals12 got called out by CityNerd:
I did not know about this intersection. I learned about it from this v. I really hope this isn't built. If you really want a 2 phase inters, just make a superstreet. Which, BTW, wasn't mentioned in the video. You can absolutely make a median U turn wide enough for trucks, despite what VDot is evidently claiming.
Quote from: ErmineNotyours on October 19, 2022, 05:37:33 PM
kernals12 got called out by CityNerd:
He doesn't give any explanation for why it's a bad design. Clearly the people who watch his channel are just supposed to know why it's bad. It's an echo chamber
Quote from: kernals12 on October 21, 2022, 10:08:43 AM
Quote from: ErmineNotyours on October 19, 2022, 05:37:33 PM
kernals12 got called out by CityNerd:
He doesn't give any explanation for why it's a bad design. Clearly the people who watch his channel are just supposed to know why it's bad. It's an echo chamber
He seemed to be high on Diamond Interchanges at the beginning of the video because people could make left turns. The rest of the video tended to poo-poo any interchange design if it didn't require all movements to make standard left turns.
Quote from: jeffandnicole on October 21, 2022, 03:18:08 PM
Quote from: kernals12 on October 21, 2022, 10:08:43 AM
Quote from: ErmineNotyours on October 19, 2022, 05:37:33 PM
kernals12 got called out by CityNerd:
He doesn't give any explanation for why it's a bad design. Clearly the people who watch his channel are just supposed to know why it's bad. It's an echo chamber
He seemed to be high on Diamond Interchanges at the beginning of the video because people could make left turns. The rest of the video tended to poo-poo any interchange design if it didn't require all movements to make standard left turns.
So he's advocating *for* more car accidents?
Quote from: kernals12 on October 21, 2022, 03:20:03 PM
So he's advocating *for* more car accidents?
Only inasmuch as you're advocate for pedestrian fatalities.
Quote from: MCRoads on October 20, 2022, 02:59:46 PM
I did not know about this intersection. I learned about it from this v. I really hope this isn't built. If you really want a 2 phase inters, just make a superstreet. Which, BTW, wasn't mentioned in the video. You can absolutely make a median U turn wide enough for trucks, despite what VDot is evidently claiming.
A reason for not doing so is the following two points. For what it's worth, the speed limit on there is 55, but traffic typically moves closer to 70 mph. I try to keep it to 60—65 when I go through that area and I don't wind up passing very many people at all. So that's a reason not to want trucks making U-turns across the median and trying to accelerate into traffic when they can.
Quote from: 1 on February 24, 2021, 08:15:17 AM
Quote from: kernals12 on February 24, 2021, 08:07:56 AM
Notice those loons. That means traffic going straight on the main road has to stop for those making a u turn. With the bowtie, all movements are done on the minor road so the smooth procession of traffic on the major road is uninterrupted.
The U-turn points usually aren't signalized; this one appears to be a rare exception. Usually, if you're on the U-turn ramp, you just merge when you can. (Some median U-turn intersections add a lane for U-turners so that they don't have to wait for a gap in traffic.)
Quote from: kphoger on October 21, 2022, 03:24:09 PM
Quote from: kernals12 on October 21, 2022, 03:20:03 PM
So he's advocating *for* more car accidents?
Only inasmuch as you're advocate for pedestrian fatalities.
Left turns are dangerous for cyclists and pedestrians too.
Quote from: tradephoric on February 24, 2021, 08:01:52 AM
Quote from: kernals12 on November 25, 2020, 09:50:40 AM
At some point in the near future, the people of Prince William County, Virginia will bear witness to a great revolution in traffic engineering. The VDOT plans to turn the current intersection between the Prince William Parkway and Clover Hill Road into a Bowtie Intersection and it is a thing of beauty
(https://i.imgur.com/Z3v26BG.png)
2 roundabouts will be installed on Clover Hill on opposite sides of the Parkway. All Left Turns at the main intersection will be prohibited and instead drivers will use the roundabouts to make a u turn to complete their movements. It's essentially an at-grade version of a dogbone interchange. It means the main intersection can use a simple 2 phase signal. It improves traffic capacity and safety.
There are many so-called innovative intersections that do the same thing such as the RCUT, the Michigan Left, the Jughandle, and the Continuous Flow Intersection, but those require a massive amount of right-of-way. This does not, in fact, as you can see, by getting rid of the need for left turn lanes, it takes up less space than a conventional intersection. I hope that this is the beginning of a glorious revolution.
Here's a Median U-turn intersection in Michigan with the same median width as Prince William Pkwy. Admittedly I'm a little partial to Median U-turns but i don't see much advantage going with the BowTie intersection in the OP's example.
(https://i.imgur.com/VSZOFO1.png)
https://www.google.com/maps/@42.7520685,-83.2466276,545m/data=!3m1!1e3
Quote from: 1 on February 24, 2021, 08:15:17 AM
Quote from: kernals12 on February 24, 2021, 08:07:56 AM
Notice those loons. That means traffic going straight on the main road has to stop for those making a u turn. With the bowtie, all movements are done on the minor road so the smooth procession of traffic on the major road is uninterrupted.
The U-turn points usually aren't signalized; this one appears to be a rare exception. Usually, if you're on the U-turn ramp, you just merge when you can. (Some median U-turn intersections add a lane for U-turners so that they don't have to wait for a gap in traffic.)
There are 2 advantages I can think of
1. It means vehicles making u-turns aren't doing it on a highway
2. Those roundabouts could be repurposed to provide access to future commercial development.
It's been two years since this thread started; has there been any movement on actually building these roundabouts?
Quote from: 1995hoo on October 21, 2022, 03:38:50 PM
For what it's worth, the speed limit on there is 55, but traffic typically moves closer to 70 mph. I try to keep it to 60—65 when I go through that area and I don't wind up passing very many people at all.
This needs a freeway treatment then. Don't even have a bowtie, just have a diamond interchange. (Perhaps double-deck the through lanes over/under the turn lanes and the cross street?) If it has high enough conflicting volumes that VDOT is even considering the bowtie, and the prevailing speed is 70, just build an interchange at that point.