Diverging Diamond Proposed in Kansas

[route56]

http://www.kansascity.com/2010/11/29/2481894/kansas-drivers-to-get-british.html

According to the Kansas City Star, a diverging diamond design is proposed for I-35 at Homestead Lane, between Edgerton and Gardner in southwest Johnson County.

Unlike other diverging-diamond proposals in the KC area, this is a new interchange. The new exit will be part of the new BNSF intermodal facility to be located in the area. Currently, the nearest exits are at Sunflower Road (202) and Gardner Road (207). Construction is slated to start in 2012.

[Revive 755]

^ If it wouldn't be so close to the Gardner Road interchange (1.3 miles estimated using the measuring tool in Google maps), I would think 199th Street would be the better spot for a new interchange; if the area is expected to develop it would be a much more useful service interchange since 199th goes a decent distance while Homestead peters out.

The KDOT website for this project needs to get the EA up.

http://i35swjohnsoncointerchange.ksdot.org/ProjectOverview.aspx

[J N Winkler]

"British treatment"?  Please.  This is more the "French treatment" because this interchange design was first used in Versailles, not that many Kansas drivers are going to be negotiating this in a Citroën DS.

[route56]

"British treatment"?  Please.  This is more the "French treatment" because this interchange design was first used in Versailles, not that many Kansas drivers are going to be negotiating this in a Citroën DS.

I think the "British treatment" is a play on the fact that drivers would be driving on the left hand side of the road.

[J N Winkler]

Yes, it is, and I suppose as a lead it is more eye-grabbing than, say, "French interchange design being tried in Kansas."  However, it tends to obscure the facts that the left-hand driving is essentially for the length of an overpass bridge, and the relative positions of the driving and overtaking lanes don't change (i.e., you drive right and overtake on the left even when you are actually on the left side of the center island, rather than driving left and overtaking right as in Britain).

[AZDude]

And I thought round abouts were bad...  I'm nervous.

[Scott5114]

I've gone through the MO 13 DDI, and it's not terrible, but if you're building from scratch, why not use a SPUI? Isn't the only real advantage of the DDI over the SPUI the fact that it can be retrofitted onto an existing bridge while the SPUI cannot?

[Revive 755]

Isn't the only real advantage of the DDI over the SPUI the fact that it can be retrofitted onto an existing bridge while the SPUI cannot?

A SPUI requires either a larger bridge deck or a longer span bridge while a DDI does not.

I'd like to see the actual justification for a DDI over a partial cloverleaf (or a diamond with the ability to add loops as needed in the future.)  I'd guess cost/ROW issues (even though there are maybe only three houses that may need to be taken now, it would be cheaper to get extra ROW now than waiting until an interchange is surrounded by commercial developments).

EDIT:  Found an old public meeting handout online that shows the old plan for this interchange was a diamond with a possible loop in the SW quadrant added in the future:
http://i35swjohnsoncointerchange.ksdot.org/PDF/4-29-2010%20Public%20Mtg%20Handout%20FINAL.pdf

[route56]

KDOT held a public open house on the interchange project this evening.

The proposal calls for two lane ramps from SB Homestead to NB I-35, and from SB 35 to NB Homestead. There will be separate NB and SB bridges. The NB bridge is two lanes, while the SB bridge is three lanes.

A DDI was picked over a SPUI because of the high volume of left-turning traffic. The loop ramp proposal was scrapped because it was determined that the loop ramp could not handle the projected capacity. A flyover ramp was rejected as too costly.

KDOT had a very nice CGI video of the interchange proposal, complete with signs, signals, and guardrails. It should be posted soon.

[Revive 755]

A DDI was picked over a SPUI because of the high volume of left-turning traffic. The loop ramp proposal was scrapped because it was determined that the loop ramp could not handle the projected capacity. A flyover ramp was rejected as too costly.

Did KDOT even consider a two lane loop, or did they just look at a single lane loop?

[route56]

Did KDOT even consider a two lane loop, or did they just look at a single lane loop?

Is there even such a thing as a two-lane loop ramp?

[okroads]

Did KDOT even consider a two lane loop, or did they just look at a single lane loop?

Is there even such a thing as a two-lane loop ramp?

The ramp from I-215 West to I-15 South in Salt Lake City has a 2-lane loop ramp.

[mightyace]

Is there even such a thing as a two-lane loop ramp?

The ramp from Moorse Lane (TN 441) EB to I-65 NB is such a ramp.

http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=Brentwood,+TN&aq=1&sll=37.0625,-95.677068&sspn=50.956929,49.658203&ie=UTF8&hq=&hnear=Brentwood,+Williamson,+Tennessee&ll=35.96519,-86.807093&spn=0.003209,0.003031&t=k&z=18

[J N Winkler]

KDOT engineering decisions are not always easy to understand.  Case in point:  I-235/US 54 interchange expansion (replacement of the present severely overloaded cloverleaf with a multi-level interchange).

At the investment study stage, two options put forward included a full Maltese cross stack (45 MPH speed on all left-turning ramps) and a stack/turban hybrid (45 MPH speed on one left-turning ramp pair and 35 MPH speed on another left-turning ramp pair).  Community consensus was strongly in favor of the Maltese cross stack option.  KDOT chose the stack/turban hybrid instead.  The design team maintains that the option chosen was, in fact, a Maltese cross stack.  I queried this decision on the K-TOC board and rapidly reached a situation where, to go any further, I would have had to tell the design team, "I'm sorry, but you are flat-out wrong about this being a Maltese cross stack," which is not a recipe for success.  Oddly enough, KDOT also proposes the same interchange type for the future K-254/US 54 interchange near Goddard.

[Henry]

KDOT engineering decisions are not always easy to understand.  Case in point:  I-235/US 54 interchange expansion (replacement of the present severely overloaded cloverleaf with a multi-level interchange).

At the investment study stage, two options put forward included a full Maltese cross stack (45 MPH speed on all left-turning ramps) and a stack/turban hybrid (45 MPH speed on one left-turning ramp pair and 35 MPH speed on another left-turning ramp pair).  Community consensus was strongly in favor of the Maltese cross stack option.  KDOT chose the stack/turban hybrid instead.  The design team maintains that the option chosen was, in fact, a Maltese cross stack.  I queried this decision on the K-TOC board and rapidly reached a situation where, to go any further, I would have had to tell the design team, "I'm sorry, but you are flat-out wrong about this being a Maltese cross stack," which is not a recipe for success.  Oddly enough, KDOT also proposes the same interchange type for the future K-254/US 54 interchange near Goddard.

Just wondering: Does anyone have an illustration of each? These two terms are new to me.

[J N Winkler]

Easier to show in Google Maps:  Maltese cross stack (I-75/US 35 in Dayton, Ohio) and stack/turban hybrid (I-25/I-40 in Albuquerque, New Mexico).

[route56]

The presentations documents from the recent meeting, including the very spiffy video of the DDI concept, have now been posted on the project website.

http://i35swjohnsoncointerchange.ksdot.org/MeetingSchedule.aspx