The Transportation and Mass Transit Megathread

[Dale]

8 minutes ago, titanhog said:

^^Does it work?  

I suspect they keep traffic moving, but don’t slow speeds through neighborhoods.

[Bos2Nash]

1 hour ago, Dale said:

I suspect they keep traffic moving, but don’t slow speeds through neighborhoods.

They seem to be a great traffic calming measure. They keep traffic moving more then a four-way stop and they do slow cars down as you still have to slow down enough to navigate around the center island. 

We encountered these a lot around Ireland on our trip and we’re really impressed with their implementation. I’ve begun thinking some intersections around our city and other US cities could really benefit from them. 

[Dale]

38 minutes ago, Bos2Nash said:

They seem to be a great traffic calming measure. They keep traffic moving more then a four-way stop and they do slow cars down as you still have to slow down enough to navigate around the center island. 

We encountered these a lot around Ireland on our trip and we’re really impressed with their implementation. I’ve begun thinking some intersections around our city and other US cities could really benefit from them. 

I’m just reporting what I observe in neighborhoods near me. Also, people purposefully shorten the lives of their cars going over speed humps (for fear of losing 5mph.)

[Mr_Bond]

2 hours ago, Dale said:

Also, people purposefully shorten the lives of their cars going over speed humps (for fear of losing 5mph.)

Now I'll slow down even more.  I'll be doing a favor to those speedsters behind me.

[Bos2Nash]

3 hours ago, Dale said:

I’m just reporting what I observe in neighborhoods near me. Also, people purposefully shorten the lives of their cars going over speed humps (for fear of losing 5mph.)

Oh I totally agree that people’s impatience prolly do keep them from slowing down. And far too often do people fly over speed bumps. I do most of my own car work, so I try my best to take of it. 

We have to start getting more creative in terms of traffic calming because things like speed bumps are non-starters on public roads. And the amount of investment in traffic signals can creep up on outrageous quickly. I also think traffic signals make things worse as people (myself included at times) speed up to make lights at times. Small traffic circles are one way of this, but it’s definitely not a “one size fits all” solution. 

[Dale]

I do like roundabouts. They keep traffic moving.

[MLBrumby]

We have them all over Chattanooga. And they keep traffic moving. Only trouble is when some dolt actually stops when there's a single car entering from the other side. 

[timmay143]

I take speed bumps at 5 mph, LOL.  Need my car to last and me saving 0.5 seconds to the next stop is not important.

[Tennessine]

13 hours ago, Dale said:

I’m just reporting what I observe in neighborhoods near me. Also, people purposefully shorten the lives of their cars going over speed humps (for fear of losing 5mph.)

Yep. It hurts me to witness people charge over those things in their expensive sedans, clipping the undercarriage.

[PaulChinetti]

I fly over rail road tracks in my 12 year old hatchback like it's a truck. Always cracks me up when I see big F-150s creeping over the things. 

Though my car is paid off... And I did just have to replace my motor mounts... Hmmm maybe there is a lesson in there somewhere. 

[tragenvol]

16 hours ago, MLBrumby said:

We have them all over Chattanooga.. 

Tremont Street!

[KJHburg]

We have those mini circles in Charlotte in some neighborhoods and also a speed table or two. That is a raised intersection that is meant to slow people down does it work not so sure about that.  

NCDOT has gone roundabout crazy all over the state.  Roundabouts are popping up in more rural areas now instead of 4 way stops,  we have roundabouts on exit ramps from our beltway I-485 and NCDOT loves diverging diamonds.   Does Tennesse have these yet?  Here is a video and these are popping up all over the state when they do a new interchange or redesign one?  I love these but my mom still closes her eyes going through one (she is not driving!)

 

[MLBrumby]

They're being built everywhere now, but (as usual) TDOT is slow to get to the construction phase. I believe one is u/c at Hickory Hollow & I-24 and I might have seen one planned for Franklin Hwy 96 at I-65 (or somewhere in Williamson). 

[PruneTracy]

12 hours ago, KJHburg said:

NCDOT has gone roundabout crazy all over the state.  Roundabouts are popping up in more rural areas now instead of 4 way stops,  we have roundabouts on exit ramps from our beltway I-485 and NCDOT loves diverging diamonds.   Does Tennesse have these yet?  Here is a video and these are popping up all over the state when they do a new interchange or redesign one?  I love these but my mom still closes her eyes going through one (she is not driving!)

Tennessee has two extant DDIs, one at US Route 129 and Middlesettlements Road in Blount County and one (unfortunately) at Interstate 40 and State Route 66 in Sevier County.

11 hours ago, MLBrumby said:

They're being built everywhere now, but (as usual) TDOT is slow to get to the construction phase. I believe one is u/c at Hickory Hollow & I-24 and I might have seen one planned for Franklin Hwy 96 at I-65 (or somewhere in Williamson). 

I don't know about State Route 96, but one is planned at the new Buckner Road interchange in Spring Hill.

[Tennessine]

29 minutes ago, PruneTracy said:

Tennessee has two extant DDIs, one at US Route 129 and Middlesettlements Road in Blount County and one (unfortunately) at Interstate 40 and State Route 66 in Sevier County.

What is a DDI? I frequently drive on Alcoa Highway (US 129) from Knoxville to Maryville, so I have probably seen this

 

Edit: Diverging Diamond Interchange?

[PruneTracy]

20 minutes ago, nativetenn said:

What is a DDI? I frequently drive on Alcoa Highway (US 129) from Knoxville to Maryville, so I have probably seen this

 

Edit: Diverging Diamond Interchange?

Yes. Here is the TDOT video (about the proposed I-24 / Hickory Hollow interchange) explaining them:

 

[markhollin]

The midstate's most vocal backers of expanded mass transit known as Moving Forward put together new leadership on Tuesday, looking to jump start support for a transit overhaul.
 

Moving Forward unveiled its new objectives. Those goals include:

1. Facilitating a regional approach to improve mobility.
2. Updating the Nashville Area Metropolitan Planning Organization's 2045 regional transportation plan in 2021, as well as the WeGo Public Transit and the Regional Transportation Authority strategic plan, called nMotion, in 2022.
3. Advocating for near-term projects to improve mobility. 
4. Identifying and securing dedicated funding for mobility in the region by 2024.
5. Beginning construction on the first phase of the WeGo and RTA strategic plan in the region by 2026.

More behind the NBJ paywall here:

https://www.bizjournals.com/nashville/news/2019/03/19/business-backed-transit-group-re-emerges-with-new.html?iana=hpmvp_nsh_news_headline

[Dale]

5 hours ago, markhollin said:

The midstate's most vocal backers of expanded mass transit known as Moving Forward put together new leadership on Tuesday, looking to jump start support for a transit overhaul.
 

Moving Forward unveiled its new objectives. Those goals include:

1. Facilitating a regional approach to improve mobility.
2. Updating the Nashville Area Metropolitan Planning Organization's 2045 regional transportation plan in 2021, as well as the WeGo Public Transit and the Regional Transportation Authority strategic plan, called nMotion, in 2022.
3. Advocating for near-term projects to improve mobility. 
4. Identifying and securing dedicated funding for mobility in the region by 2024.
5. Beginning construction on the first phase of the WeGo and RTA strategic plan in the region by 2026.

More behind the NBJ paywall here:

https://www.bizjournals.com/nashville/news/2019/03/19/business-backed-transit-group-re-emerges-with-new.html?iana=hpmvp_nsh_news_headline

Does the airport rail connection figure into this, or is it separate ?

[PaulChinetti]

I was thinking yesterday as I was driving around, any of these plans is going to need to take zoning around any/all of the stops into consideration and increase it. Stops with 3 houses around them don't make as much sense as stops with 3 apartment buildings around them. 

[Vrtigo]

23 hours ago, nativetenn said:

What is a DDI? I frequently drive on Alcoa Highway (US 129) from Knoxville to Maryville, so I have probably seen this

 

23 hours ago, PruneTracy said:

Yes. Here is the TDOT video (about the proposed I-24 / Hickory Hollow interchange) explaining them

Is the McEwen Drive interchange in Franklin considered a DDI? If so, that might be a good example that more people would be personally familiar with.

[downtownresident]

6 minutes ago, Vrtigo said:

 

Is the McEwen Drive interchange in Franklin considered a DDI? If so, that might be a good example that more people would be personally familiar with.

McEwen is a SPUI, or a Single Point Urban Interchange.

[PruneTracy]

9 minutes ago, Vrtigo said:

Is the McEwen Drive interchange in Franklin considered a DDI? If so, that might be a good example that more people would be personally familiar with.

2 minutes ago, downtownresident said:

McEwen is a SPUI, or a Single Point Urban Interchange.

That's right. SPUIs are much more common both in Tennessee and nationwide. There are also examples in Nashville on Briley Parkway at Murfreesboro Pike (near the airport) and McGavock Pike (near Opryland). Bill Morris Parkway in Memphis (SR 385) has eight SPUIs which is all but one of its service interchanges.

DDIs and SPUIs were developed to serve similar goals, which is to facilitate heavy left-turn volumes at interchanges. The difference is that SPUIs are better at servicing opposing left-turns either from the ramps or the crossing road (but not necessarily both), while DDIs are better at servicing conflicting left-turns both from the ramp and the crossing street (although they do fine with opposing left turns too). But as shown at Bill Morris Parkway SPUIs are a good overall design for interchanges even if left turns aren't a problem (if you don't mind paying for larger bridges) because they only require one traffic signal, they're cheaper to construct, and you don't have the "TDOT is tripping balls" effect that people get driving through a DDI. They are also both generally for more compact, urban or suburban interchanges where right-of-way is a limiting factor; there are more efficient, conventional designs if you have more ROW available which is why the DDI in Sevier County is irritating.

2 hours ago, PaulChinetti said:

I was thinking yesterday as I was driving around, any of these plans is going to need to take zoning around any/all of the stops into consideration and increase it. Stops with 3 houses around them don't make as much sense as stops with 3 apartment buildings around them. 

The flip side of this is that areas not near transit corridors would need to be downzoned to keep high-density developments from being sited away from transit stops. And of course having a government willing to enforce both.

[PaulChinetti]

8 minutes ago, PruneTracy said:

The flip side of this is that areas not near transit corridors would need to be downzoned to keep high-density developments from being sited away from transit stops. And of course having a government willing to enforce both.

Having a government willing to do anything with zoning. I am not going to hold my breath. 

[MidTenn1]

Inside baseball; The first DDI was not welcomed warmly by TDOT design staff. It was shoved on TDOT by a prominent consulting engineering company who used their political clout to make it happen. It does make a nice item in their portfolio, however. 

 And that's how sausage is made my freinds.

[MidTenn1]

And the SPUI in Murfreesboro was ideally supposed to operate as a three phase signal operation with the standard SPUI design. HOWEVER, a few locals wanted to add an additional ramp to downtown which would have required an additional phase resulting in operational failure. I pointed this out in a design meeting in which the consulting engineer said it's going to fail anyway...implying he didn't care, just send me my check.

Fortunately, the project was tabled for a few years and finally built properly. You're welcome.