Diverging Diamond Intersection at FM 60 & 2818

redd38
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91_Aggie said:

Ah. So you never wanted that intersection to change. You never wanted lights to go up for the traffic on hwy 60?
I see now.

I would imagine that lights were going to go up and they decided to use this model of intersection instead of one that we are more familiar with.

With the growing population, the medical school, and Rellis campus that intersection was not going to stay the little ol' country road it used to be.

Lights were going up whether they did it this way or with a more familiar method.


JFC, how back and read my posts. I feel like you're responding without actually reading the thread. My entire argument is DDI vs 2 lights in a traditional configuration. Try again.

Still waiting for you to prove me wrong.
redd38
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pants said:

To redd38: You always make both green lights on diamond interchanges?

I get the point about always having to stop at at least one light on the new design, but with a traditional design, you will get stopped sometimes.


For the vast, vast majority of the day both lights can be green for traffic traveling straight on 60 and blinking yellow arrows for left turns into 2818. No need to cycle, just leave it like that all day except for the 2 hours when there's actually traffic out there.

So yes, for the vast majority of the day everyone would make both green lights.
91_Aggie
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Each side of the crossing was going to be a 4 way intersection.

There was going to be lots of people stopping at this new intersection.

You may to have to show the video of whatever you are thinking about. It seems like you just want to make sure the people on 60 that want to stay on 60 never have to stop twice.

Again if those people have to stop twice but the overall flowrate is faster than in a traditional intersection then this method is better.

Maybe it wont work out that way. I doubt you would accept any proof even after it is in place unless they measured the flow rate for a year, then tore it down and put in your traditonal intersection and then measured it again.

91_Aggie
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redd38 said:

pants said:

To redd38: You always make both green lights on diamond interchanges?

I get the point about always having to stop at at least one light on the new design, but with a traditional design, you will get stopped sometimes.


For the vast, vast majority of the day both lights can be green for traffic traveling straight on 60 and blinking yellow arrows for left turns into 2818. No need to cycle, just leave it like that all day except for the 2 hours when there's actually traffic out there.

So yes, for the vast majority of the day everyone would make both green lights.


So in your scenario no growth/increase in traffic happens at this intersection that has a nearby airport, a gowing TAMU medical center, and a growing Rellis campus right down the road?

I'm pretty sure the traffic engineers are taking into consideration many other factors other than the current traffic patterns.

LOYAL AG
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Traffic planners and football coaches are the two professions where the best of the bunch are always busy doing something else to earn a living.
redd38
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91_Aggie said:

redd38 said:

pants said:

To redd38: You always make both green lights on diamond interchanges?

I get the point about always having to stop at at least one light on the new design, but with a traditional design, you will get stopped sometimes.


For the vast, vast majority of the day both lights can be green for traffic traveling straight on 60 and blinking yellow arrows for left turns into 2818. No need to cycle, just leave it like that all day except for the 2 hours when there's actually traffic out there.

So yes, for the vast majority of the day everyone would make both green lights.


So in your scenario no growth/increase in traffic happens at this intersection that has a nearby airport, a gowing TAMU medical center, and a growing Rellis campus right down the road?

I'm pretty sure the traffic engineers are taking into consideration many other factors other than the current traffic patterns.




None of the traffic to any of the things you listed (airport, medical center, Rellis) changes the problem with that intersection. The traffic to each of those could increase 10-fold and the previous incarnation of that intersection would have been fine. The problem with the intersection was people turning left to exit 60 onto 2818. That is what the new solution addresses. In fact, traffic to and from those three places support my argument to allow free flow of traffic on 60. Which I STILL haven't been proven wrong about.
1939
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We will see how this works out, I personally think that traffic there is not heavy enough to warrant the diverging diamond.

Also, this is similar but not the same as the setup as at 35/21 in San Marcos, there only the left turn lanes switch sides and thus you can only be stopped by a light on one side of the intersection, the main lanes stay on the right side of the road.
jamesf
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The beauty of the diverging diamond is that it takes away two cycles from the traffic signal. In a typical signal, you have four cycles (road 1 left, road 1 through, road 2 left, road 2 through). The DDI removes two cycles so that more traffic is able to progress through the intersection in the same amount of time. Plus, left turn movements can be made unencumbered with a traffic signal.

You can see the layout of this intersection at the link below.

https://www.txdot.gov/inside-txdot/projects/studies/bryan/fm60.html
histag10
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Has anyone figured out how you would proceed if you exit 2818 on to 60 to make a u turn back onto 2818?

Seems like it's not possible with this setup.
Tee
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If you look closely at the video, cars are running over each other ( the computer simulation). Not sure how reliable it is.
LOYAL AG
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redd38 said:

91_Aggie said:

redd38 said:

pants said:

To redd38: You always make both green lights on diamond interchanges?

I get the point about always having to stop at at least one light on the new design, but with a traditional design, you will get stopped sometimes.


For the vast, vast majority of the day both lights can be green for traffic traveling straight on 60 and blinking yellow arrows for left turns into 2818. No need to cycle, just leave it like that all day except for the 2 hours when there's actually traffic out there.

So yes, for the vast majority of the day everyone would make both green lights.


So in your scenario no growth/increase in traffic happens at this intersection that has a nearby airport, a gowing TAMU medical center, and a growing Rellis campus right down the road?

I'm pretty sure the traffic engineers are taking into consideration many other factors other than the current traffic patterns.




None of the traffic to any of the things you listed (airport, medical center, Rellis) changes the problem with that intersection. The traffic to each of those could increase 10-fold and the previous incarnation of that intersection would have been fine. The problem with the intersection was people turning left to exit 60 onto 2818. That is what the new solution addresses. In fact, traffic to and from those three places support my argument to allow free flow of traffic on 60. Which I STILL haven't been proven wrong about.
Actually IMO the bigger problem was people turning left onto 60 from 2818. During morning rush that traffic was often stacked so deep that both sides were sitting in the straight lanes waiting to get into the turn lane. Worse still you had the occurrence when the turn lanes weren't stacked up and you had folks changing into the turn lanes from opposite directions at 60 MPH heading right towards each other because that space was used for people turning east and west onto 60. That's quite obviously bad and nothing in the previous incarnation of that intersection was going to make that better.

The existing interchange was dangerous on both 2818 and 60 and a light wasn't going to help anything at all other than to slow things down for everyone. The math shows that this arrangement will handle significantly more traffic than what you're proposing and it's really not close and it will handle it in a safer manner by eliminating the left turns across traffic.
LOYAL AG
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histag10 said:

Has anyone figured out how you would proceed if you exit 2818 on to 60 to make a u turn back onto 2818?

Seems like it's not possible with this setup.
That's really not where you want to do a U turn, is it? There are lights at both F&B and Bush where a u turn can be done significantly more safely than they can at 60.
jello123
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My prediction... Criss-Cross-Crash.
trouble
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There's one in Round Rock. It didn't take long for people to get used to it and it helped a ton with congestion by the outlet mall.
91_Aggie
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histag10 said:

Has anyone figured out how you would proceed if you exit 2818 on to 60 to make a u turn back onto 2818?

Seems like it's not possible with this setup.

Watch the video starting at about the 40 second mark (43 second mark shows the arrows for that).


The only thing I see that will be annoying is if you exited from 2818 to 60, but made a mistake and wanted to get back on 2818. It looks like you will have to go down 60 in either direction until you can turn around in some manner.

Since there is the aggie cemetery and airport on the side going to Snook, and research Park (and probably A&M property) on the other side. People shouldn't be exiting there to stop at a future gas station or shopping center and then not being able to easily get back on to 2818. So, it would only affect people who made a bad decision to exit 2818 there.
pants
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I don't think any of us have current traffic counts for this interchange, much less projected counts for years to come.

It's clear to me that the DDI design is a good one for handling larger traffic volumes, so if projected volumes are high enough, I applaud the effort to pre-emptively improve this interchange. I typically complain about construction not even starting until the problem is already bad. Assuming traffic gets worse here, nice job getting ahead of it!
EBrazosAg
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I think the bigger issue is going to be the changes on 2818 intersections between Wellborn and 60 that are coming up, although something is certainly needed at the "suicide turn lanes" in front of several of the apartment complexes. Going straight across 2818 is going to require turning right, then a u-turn back and another right turn at several intersections if I recall the scheme correctly......
duffelpud
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These computer sims are great, but they don't show what happens when a driver looking at their cell phone rear-ends another car and subsequent drivers start to snapchat it all while trying to navigate this unicorn interchange.

I'd like to see the 'flow rate' on that situation.
"What's this button do?"
chigger
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Driving through it really doesn't feel that weird. The only differnent thing is the lights situated at an angle. Other than that it just feels like you are driving straight through.

Again, it really isn't a big deal. It's design is meant to make it easier, not harder.
75AG
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chigger said:

Driving through it really doesn't feel that weird. The only differnent thing is the lights situated at an angle. Other than that it just feels like you are driving straight through.

Again, it really isn't a big deal. It's design is meant to make it easier, not harder.
It's different. It's bad.
91_Aggie
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duffelpud said:

These computer sims are great, but they don't show what happens when a driver looking at their cell phone rear-ends another car and subsequent drivers start to snapchat it all while trying to navigate this unicorn interchange.

I'd like to see the 'flow rate' on that situation.
Gonna have that problem at any intersection. Can't prevent dumb no matter how the intersection is setup.

trouble
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duffelpud said:

These computer sims are great, but they don't show what happens when a driver looking at their cell phone rear-ends another car and subsequent drivers start to snapchat it all while trying to navigate this unicorn interchange.

I'd like to see the 'flow rate' on that situation.


The soccer moms at the outlet mall figured it out. Students will too.
pants
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Unicorn? Does that mean you think they're rare, and you're humoring the inexperienced designer who doesn't understand that this design won't work?

As it turns out, this has been used extensively in the US and has proven to be cheap to build compared to other solutions for 60 and 2818, safer than other designs, and more efficient. If you think this is a "unicorn" interchange, maybe you're just unfamiliar with its widespread use. Check the map here: https://divergingdiamond.com

It's amazing how many people think they're experts in traffic engineering with no experience other than driving on roads. It would be like me judging a bridge design to be faulty before it's even built because hey, I drive on bridges all the time!

Edit: This is all assuming you're not a practicing traffic engineer. If you are, I apologize in advance.
75AG
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Nah, it was probably designed by someone on the TexAgs Politics board.
FlyRod
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Once again, the construction projects around town are far less bothersome than the townies who seem completely incapable of navigating them.
fourth deck
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Drove on one of these up in Asheville and it wasn't awkward at all. All of the markings/medians/barriers did a good job of taking away any confusion. The only better option is an SPUI. Have one of these by my house and having to wait for only 1 light to cross is great.

91_Aggie
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redd38 said:

pants said:


It's amazing how many people think they're experts in traffic engineering with no experience other than driving on roads. It would be like me judging a bridge design to be faulty before it's even built because hey, I drive on bridges all the time!


What do you think

Don't worry, it was designed by experts.


This guy makes a post and adds a smiley face for a video that shows multiple people dying.

Staff. You have said many times this is not the General Board. Time to clean this up.


[We aren't on here 24/7. Use the voting function. -Staff]
histag10
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EBrazosAg said:

I think the bigger issue is going to be the changes on 2818 intersections between Wellborn and 60 that are coming up, although something is certainly needed at the "suicide turn lanes" in front of several of the apartment complexes. Going straight across 2818 is going to require turning right, then a u-turn back and another right turn at several intersections if I recall the scheme correctly...


I always thought that 2818 should have been designed like most loops in other towns- with a feeder road, under/over passes, and ramps.
histag10
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LOYAL AG said:

histag10 said:

Has anyone figured out how you would proceed if you exit 2818 on to 60 to make a u turn back onto 2818?

Seems like it's not possible with this setup.
That's really not where you want to do a U turn, is it? There are lights at both F&B and Bush where a u turn can be done significantly more safely than they can at 60.


I think you are misunderstanding me. Most places (BCS not so much) discourage u-turns in the middle of intersections and at lights. Typically, when a road has a ramp on and off with an overpass/underpass, you are able to U-turn back into the road you exited off of by going off the ramp, and hanging 2 lefts (one onto the overpass, and one on the other side of the overpass - Like HWY 6). Doesn seem possible here.
fourth deck
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It's pretty straightforward to pull U-y on this design. Just turn left onto the bridge and then you have another left directly back onto the on-ramp going the opposite way without having to wait on a 2nd light or contend with oncoming traffic.
redd38
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pants said:


The only possibly valid argument you've made is to ask whether we need a major change - whether there will be enough of a traffic volume increase at that intersection to warrant a new design.


How many valid arguments do I need to make??? Is one not enough?

You say the new design is safer, more efficient, and cheaper. However, just adding 2 lights to the (previously) existing layout would have been monumentally cheaper (agree?), equally as safe (agree?), and more efficient 90% of the time (agree?). I will agree that the DDI is more efficient for 10% of the day (but how much more efficient?). So why spend millions of dollars for such a small improvement?

It might only be one valid argument, but it's a pretty damn good argument.
redd38
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Wait till y'all see what they're gonna do at Holleman



Not sure how I feel about that one yet.
fourth deck
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That will be annoying AF for anyone wanting to continue on Holleman across Harvey Mitchell. Would be better to make Harvey Mitchell an overpass than wast money on that.
WheelinAg
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They have that Holleman setup on 281 north of San Antonio, it's pretty annoying. I will use the diverging diamond twice a day though...
91_Aggie
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With everyone being lawsuit happy in today's world, it looks like TXDOT/TTI are moving to "better safer than the MOST convenient" roadways and intersections.

So, while it may be more efficient for certain people based on their daily routes, but is overall more dangerous for others, then they are going to build the "safer" option.

If there is an accident and the lawyer asks "When you designed this intersection, what led you to pick this specific design when there was a proven safer design that could have been implemented? It appears you were criminally negligent because you were worried about saving some people 1 minute on their commute. Is 1 minute in commuting time savings really worth the lives that were lost due to your negligence?!?! No, you don't need to answer... everyone knows the answer... except apparently you"

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