Fads in highway construction

[hbelkins]

For quite some time, it seemed like SPUI's were the big fad in highway construction projects.

What now?

I'd say it's a tie between roundabouts and diverging diamond interchanges. Both seem to be quite popular at the moment.

What else could be described as faddish when it comes to highway projects, either at some point in the past, currently, or possibly in the future?

[J N Winkler]

I am not sure fad is the right word since the implication is that there is a subsequent decline in popularity, whereas I suspect the reality is that a saturation point is reached after a while as the existing opportunities to deploy a design innovation are exhausted.  Old, unfashionable clothes get taken to the Goodwill, but highway infrastructure is more durable, so there are still lots of SPUIs hanging around even though relatively few are being built at present (I-40 Morgan Road in Oklahoma City vicinity being one example); I haven't heard of any SPUIs being demolished and replaced with something else.  I expect much the same to happen with roundabouts and DDIs.  (Eventually we may reach a point where it is considered advantageous to convert roundabouts to "hamburgers," as has been done with several major roundabouts in Britain, but I think we are still a long way off from that.)

The design change that has the largest potential to be a fad in the classic sense is Clearview, and that is largely because--unlike SPUIs, DDIs, and roundabouts--it is a fashion choice rather than a substantial design improvement.

[wriddle082]

Tennessee seems to have stopped constructing Jersey barriers, both as median dividers and bridge parapets, in favor of constant slope barriers.  So far, I think I've only additionally seen them used in Georgia, but I don't get out to other states as frequently as I used to.

[agentsteel53]

convert roundabouts to "hamburgers,"

what would be the advantage of this intersection design?  in order to make a left turn off the mainline, you would have to cross all the lanes, as opposed to just the opposing ones.  seems to me that a mutual left-turn lane would be a better design in this case.

[agentsteel53]

as far as fads go, I cannot think of any.  there are certainly improvements in expertise which have deprecated certain construction types (cloverleafs, left exits/entrances, sharp RIROs onto freeways, etc) but none of those have been arbitrarily abandoned, like pet rocks and (hopefully) Clearview.

[roadman]

as far as fads go, I cannot think of any.  there are certainly improvements in expertise which have deprecated certain construction types (cloverleafs, left exits/entrances, sharp RIROs onto freeways, etc) but none of those have been arbitrarily abandoned, like pet rocks and (hopefully) Clearview.

My vote for current improvements that history will (hopefully) view as fads one day goes to Arrow Per Lane signs.

[Scott5114]

The SPUI fad is just now hitting the Oklahoma City area–the I-40 Morgan Road SPUI has been followed up by I-35 Main Street in Norman (which just opened a week or so ago), and another is in the plans for the next interchange south of Main Street (Lindsey Street).

[briantroutman]

I think the "fad"  aspect comes in–not so much in the Pet Rock sense–but in the sense that a trendy option is considered first and in greater depth than (or to the exclusion of) other alternatives.

Because the fixtures of highway infrastructure are durable to the point that service lives are typically measured in decades, we're obviously not going to see design features appear and disappear within a few years time. Even Clearview (if it's finally condemned by the FHWA) likely won't disappear until all of the guides have reached the end of their serviceable lives 10 or 20 years from now.

But I think the relatively quick change in policy  is as fad-like as anything in highway construction can be.

[jeffandnicole]

convert roundabouts to "hamburgers,"

what would be the advantage of this intersection design?  in order to make a left turn off the mainline, you would have to cross all the lanes, as opposed to just the opposing ones.  seems to me that a mutual left-turn lane would be a better design in this case.

I'm going to use NJ 70 & 73 as an example.  73 was the 'burger' which went thru the circle, and 70 followed the circle loop.

In order to make a left from Rt. 73, traffic on 73 had to turn right then go thru the circle.  Of course, NJ didn't factor in things like merge lanes, so the traffic waiting within the circle mixed in all so carefully (ha) with traffic on Rt. 70. 

Now, traffic on Rt. 70 that wanted to turn left onto Rt. 73 simply did so at the burger...traffic didn't have to loop all the way around.

The net result...it can add capacity and helps for a little bit, but it's not the greatest of designs.  Another case in point: The circle near the Atlantic City Airport was converted from a normal Jersey Circle to a 'Hamburger'...and congestion severely increased due to traffic light timings.  I remember at the time the local politicians and project engineers insisted the design was better...although that didn't appease motorists that saw minor or no congestion suddenly become a several minute wait to get thru the area (I'm guessing the timings got better, people stopped complaining, or the local paper stopped reporting on it).

[roadman]

Even Clearview (if it's finally condemned by the FHWA) likely won't disappear until all of the guides have reached the end of their serviceable lives 10 or 20 years from now.

As use of Clearview by individual states is still subject to interim approval, if (when?) FHWA condemms it, they could mandate that those states revise their signs back to Highway Gothic within a given time frame.  But you're right.  Chances are very high that FHWA would likely allow existing Clearview signs to remain in place until the end of their service life.

[Henry]

I'll say turbine interchanges are the current fad, as the only one I knew with that design was the Circle Interchange in my hometown, and more are being built now.

[vdeane]

convert roundabouts to "hamburgers,"

what would be the advantage of this intersection design?  in order to make a left turn off the mainline, you would have to cross all the lanes, as opposed to just the opposing ones.  seems to me that a mutual left-turn lane would be a better design in this case.

I'm going to use NJ 70 & 73 as an example.  73 was the 'burger' which went thru the circle, and 70 followed the circle loop.

In order to make a left from Rt. 73, traffic on 73 had to turn right then go thru the circle.  Of course, NJ didn't factor in things like merge lanes, so the traffic waiting within the circle mixed in all so carefully (ha) with traffic on Rt. 70. 

Now, traffic on Rt. 70 that wanted to turn left onto Rt. 73 simply did so at the burger...traffic didn't have to loop all the way around.

The net result...it can add capacity and helps for a little bit, but it's not the greatest of designs.  Another case in point: The circle near the Atlantic City Airport was converted from a normal Jersey Circle to a 'Hamburger'...and congestion severely increased due to traffic light timings.  I remember at the time the local politicians and project engineers insisted the design was better...although that didn't appease motorists that saw minor or no congestion suddenly become a several minute wait to get thru the area (I'm guessing the timings got better, people stopped complaining, or the local paper stopped reporting on it).

What is a "hamburger"?

[sammi]

What is a "hamburger"?

A hamburger interchange is just like a roundabout, but with one road going through, instead of under/over, the roundabout.

[1995hoo]

What is a "hamburger"?

A hamburger interchange is just like a roundabout, but with one road going through, instead of under/over, the roundabout.

(image omitted)

I think that's Fairfax Circle, which is located near where I grew up. It's not really a true roundabout for a host of reasons, including the tangent lanes on two sides. It illustrates one of the quirks of the "hamburger" design: Traffic on the non-"hamburger" road (in this case, VA-237 and US-29, entering from the bottom and top of the image, respectively) can make left turns onto the "hamburger" portion because of the one-way circulation on the circle. There's no reason not to allow that maneuver. Traffic on US-50 (the "hamburger") has to go around the circle (and get stuck at another traffic light) in order to make the left-turn maneuver because allowing left turns from the "hamburger" would lock up the circle.

One of the things I hate at Fairfax Circle is that there is no turn on red if you want to make a right turn from US-50–for example, if the white truck at the left side of the image wants to make a right past the Shell station and head down VA-237, he has to sit there at the red light because there's no turn on red. That spot has been reconfigured from what's shown in the image above, incidentally, to provide more pedestrian protection, but the "No Turn on Japan" signs remain (see here: https://www.google.com/maps/@38.86446,-77.276052,3a,75y,99.89h,84.67t/data=!3m4!1e1!3m2!1s3-fN7FGka6onWR4q5j_MsA!2e0 )

I've always thought this style of circle works better when the "hamburger" road uses an underpass, though obviously that in turn is more expensive to build and may require more space depending on the design.

[roadman]

The current configuration of Bell Circle in Revere (MA), where MA 60 and MA 1A split/join is a good example of a 'hamburger' design.  However, in that case, traffic on the outside perimeter is not allowed to make direct left turns onto the bisecting roadway.

[J N Winkler]

convert roundabouts to "hamburgers"

what would be the advantage of this intersection design?  in order to make a left turn off the mainline, you would have to cross all the lanes, as opposed to just the opposing ones.  seems to me that a mutual left-turn lane would be a better design in this case.

The main rationale for roundabout-to-hamburger conversion is to secure an incremental improvement in traffic flow at a location where a more competent improvement (such as a grade separation) is not possible to build for planning reasons.  I used to live fairly near this example:

A40 Headington Roundabout, Oxford

In this case, the hamburger roadway serves a right turn (the A40 westbound turns here to bypass Oxford to the north).  Before it was built, the roundabout was already signalized, which roundabouts tend to need to prevent lockup when they handle traffic volumes in excess of 20,000 VPD.  The hamburger roadway gives westbound traffic coming off the A40 Wheatley bypass (some of which stays on the A40 and some of which continues straight ahead into Oxford proper) more lanes, which reduces queue depth and intersection delay.

You could argue that instead of resorting to a hamburger conversion, Oxfordshire County Council should have grade-separated Headington Roundabout.  But this is a large-scale improvement because of the demolition that would be required (essentially everything in the immediate vicinity of the roundabout, as opposed to nothing for the hamburger conversion), and the economic case cannot be considered in isolation from the costs and benefits of grade-separating other flat intersections on the Oxford ring road.  Since the Oxfordshire structure plan (somewhat similar to an American MPO's constrained long-range plan, except it includes housing as well) embodies a policy that car commuting will be discouraged in favor of other modes, a decision to grade-separate the entire Oxford ring road will be a long time in coming if it ever arrives.  This leaves  plenty of time to milk the benefits of smaller-scale improvements such as hamburger conversion; forgoing it on the basis that the roundabout should be grade-separated instead would amount to making the perfect the enemy of the good.

I'll say turbine interchanges are the current fad, as the only one I knew with that design was the Circle Interchange in my hometown, and more are being built now.

I don't think there is anything particularly faddish about turban interchanges--there are plenty of others from approximately the same time period as the Circle Interchange:  I-40/I-27 in Amarillo, I-135/US 54 in Wichita, etc.  What does seem to be fashionable at the moment is stack/turban hybrids, like the Big I (I-25/I-40 interchange) in Albuquerque, planned I-235/US 54 in Wichita (a cloverleaf upgrade), planned K-254/US 54 near Goddard, etc.  I don't understand why agencies prefer them to true stacks because the opposite-facing left-turning direct connectors that cross in plan (the "turban" element of the design) seem to entail more bridge deck square footage and lower design speeds, both of which are disadvantages compared to a true stack design.

My vote for current improvements that history will (hopefully) view as fads one day goes to Arrow Per Lane signs.

Given the thin evidence base for them (tachistoscope studies only), their great cost in terms of sign panel area, and the problems they cause with ramp divergences and closely spaced exits, I'd say the odds for eventual discard are more favorable on this one than on many others.  GMITC has talked about getting FHWA to legitimize "sawn-off" OAPLs (OAPLs that omit the pull-through information), so this may signal the beginning of a retreat from the OAPL concept.

[lepidopteran]

Fads that I've observed, though I realize that some of these are based on practicality rather than style:

• From the mid-'70s to most of the '80s, using a half-Jersey-wall, only, as a bridge parapet.  Formerly, most freeway bridges used tubular steel parapets, often but not always angled or curved inward somehow.  But eventually, tubular steel parapets made a return, though usually atop the safety taper of a Jersey wall. (In Ohio, if the bridge was only over water, a regular guardrail would often suffice.)


• Two other parapet-related fads:  I think this was mostly in Michigan, a blocky concrete "railing" with openings, sometimes with a tubular metal railing on top.  IIRC, some of these were retrofitted with a Jersey wall blocking the openings, when that fad started.
  Another, much older fad, if we can call it that, was a flat concrete parapet with "corrugated" openings.


• Fluorescent street lighting.  This was popular in the late-60s/early-70s.  The fixtures had a long, angled head.  I suspect that these were popular because they were "cool" looking, at least at the time.


• Another street light style where both the pole and the head were colored brown, the pole usually had a square cross section, the head was square shaped, and there was little or no space between the head and the pole.  I saw some of these at a rest area under construction in the mid-80s on I-95 in Florida.


• Trapezoidal box girders, either steel or concrete, seemed to be popular in stack-like interchange projects of the '80s.  Now I only seem to see them used in water crossings or in rapid-transit systems.


• Bridge beams made from weathering steel, better known by the brand name COR-TEN.  I thought I heard that the problem was when salt was applied to the overhead road and leaked down on the structural steel.


• Bicycle lanes in a city separated by a flat concrete divider.  Granted, I only know of two of these locations.  One reason for eliminating them I heard was there was no simple way to remove trash that accumulated in the lanes.  Today, of course, bike lanes, if not a separate paved "trail", are demarcated with paintbrush stripes, maybe with a few diamonds.


• Painting Interstate shields on the pavement, in color, prior to ambiguous interchanges.  Did this ever catch on?


• How about arrows pointing upward, diagonally toward the right, rather than at a downward angle?


• Metric signs in the US, except in certain states.  Though except for the metric speed limits in Florida in the '80s, I can only think of a handful of locations where I ever saw them.

[Revive 755]

I haven't heard of any SPUIs being demolished and replaced with something else.

The SPUI at I-74 and 7th Avenue in Moline, IL, will be removed as part of the Mississippi River bridge replacement project.

Fads that I've observed, though I realize that some of these are based on practicality rather than style:

• Bicycle lanes in a city separated by a flat concrete divider.  Granted, I only know of two of these locations.  One reason for eliminating them I heard was there was no simple way to remove trash that accumulated in the lanes.  Today, of course, bike lanes, if not a separate paved "trail", are demarcated with paintbrush stripes, maybe with a few diamonds.

The separate bike lanes are making a comeback, although in this iteration there are flexible posts instead of a concrete divider -Dearborn Street in Chicago is an example of this new form.

[froggie]

The separate bike lanes are making a comeback, although in this iteration there are flexible posts instead of a concrete divider -Dearborn Street in Chicago is an example of this new form.

Not always.  I believe some of the newer Manhattan bike lanes are curb-separated, as are two brand new cycletracks currently under construction in DC.

[J N Winkler]

Fads that I've observed, though I realize that some of these are based on practicality rather than style:

(snip)

Trapezoidal box girders, either steel or concrete, seemed to be popular in stack-like interchange projects of the '80s.  Now I only seem to see them used in water crossings or in rapid-transit systems.

These are still being built--from memory, this type of box girder was used for both stacks on the Katy Freeway expansion (I-10 west of Houston).

Bridge beams made from weathering steel, better known by the brand name COR-TEN.  I thought I heard that the problem was when salt was applied to the overhead road and leaked down on the structural steel.

Weathering steel is still being used--in fact, since 2012 Florida DOT has had a policy that all new steel I-beam and box girder bridges will use weathering steel whenever feasible.  Weathering steel does have its problems.  In order to work properly, it needs time in moist air to develop the patina that stops further corrosion.  Deicing chemicals can cause it to corrode too rapidly for this to happen before significant section loss sets in, while in desert air the patina hardly ever develops (this is a problem in Arizona, for example).  In addition, the piers have to be detailed carefully so that rusty water draining off the girders does not stain bare concrete.  However, weathering steel has compelling advantages both for the environment and for the state DOT's bottom line.  Since it does not have to be painted, it saves 10% at construction and 30% over the bridge life cycle compared to painted girders while also eliminating VOCs from new paint and toxic chips from old paint.

There are a couple of flyover bridges being built near me as part of the I-235/13th Street project in Wichita--I haven't checked against the plans yet, but I suspect the girders are weathering steel.

Painting Interstate shields on the pavement, in color, prior to ambiguous interchanges.  Did this ever catch on?

Yup!  In the MUTCD (since 2003, I think--definitely since 2009 at least), and I see them every so often in construction plans.

How about arrows pointing upward, diagonally toward the right, rather than at a downward angle?

I'm not sure what you mean by this--most exit direction signs do still have arrows pointing upward and diagonally to the right.

Metric signs in the US, except in certain states.  Though except for the metric speed limits in Florida in the '80s, I can only think of a handful of locations where I ever saw them.

California's dual-unit signs (introduced in the 1970's) are deprecated now and have been removed from the sign specs collection.  However, Arizona is still keeping metric signs on I-19.  South Dakota has dual-unit signs which are still being replaced in kind.

[lepidopteran]

Fads that I've observed, though I realize that some of these are based on practicality rather than style:

How about arrows pointing upward, diagonally toward the right, rather than at a downward angle?

I'm not sure what you mean by this--most exit direction signs do still have arrows pointing upward and diagonally to the right.

Oh, I should have been clearer here.  I meant overhead BGS's that tell multiple lanes where to exit, especially for "high-speed" splits.  Pretty sure the standard method is to point the arrows downward at an angle to the right, with arrows on the sign over the through lanes pointing straight down, one arrow per lane.  But I used to occasionally see them with the arrows pointed upward to the right.  I thought this was a fad, unless there's a difference in meaning that I'm not aware of (about to ascend an obvious hill, perhaps?)

[J N Winkler]

I haven't heard of any SPUIs being demolished and replaced with something else.

The SPUI at I-74 and 7th Avenue in Moline, IL, will be removed as part of the Mississippi River bridge replacement project.

This is true.  However, detailed study of the FEIS shows that the new crossing is being built substantially to the east of existing I-74, presumably to allow I-74 to remain open to traffic during construction.  The 7th Avenue SPUI is right at the point where the new alignment joins the new one, so it is not so surprising that the new configuration will not only not be a SPUI, but will also entail fairly indirect connections between I-74 and 7th Avenue for some movements, notably westbound 7th to southbound (book eastbound) I-74 and southbound I-74 to both directions of 7th.

Here in Wichita, the I-235/US 54 upgrade will affect the West Street SPUI immediately to the east since the overpass will have to be widened to accommodate ramp braiding, but US 54 is remaining substantially on its existing line, so as far as I know West Street will still retain the SPUI configuration.

[Zeffy]

I'm not sure what you mean by this--most exit direction signs do still have arrows pointing upward and diagonally to the right.

I think he means signs like this:



Rather than:

[J N Winkler]

How about arrows pointing upward, diagonally toward the right, rather than at a downward angle?

I'm not sure what you mean by this--most exit direction signs do still have arrows pointing upward and diagonally to the right.

Oh, I should have been clearer here.  I meant overhead BGS's that tell multiple lanes where to exit, especially for "high-speed" splits.  Pretty sure the standard method is to point the arrows downward at an angle to the right, with arrows on the sign over the through lanes pointing straight down, one arrow per lane.  But I used to occasionally see them with the arrows pointed upward to the right.  I thought this was a fad, unless there's a difference in meaning that I'm not aware of (about to ascend an obvious hill, perhaps?)

Thanks for the clarification.  Actually, the method with the lane assignment arrows pointing diagonally upward is now the standard one.  What you describe (arrows pointing diagonally downward) is called "dancing arrows" and is officially not allowed as of MUTCD 2009.  Previously (up to and through the validity period of MUTCD 2003), the standard solution was to use arrows that pointed straight down--no "dancing"--for both the through and exiting movements.

This is actually an interesting question.  An argument can be made for both approaches--"dancing arrows" and lane assignment arrows pointing diagonally upward--being fads.  Both have been around for a long time without any mention in the MUTCD.  However, I think I'd put my money on the diagonally upward lane assignment arrows staying the course, because (1) they look neater, (2) they now have official recognition in the MUTCD while the other approach is now forbidden, and (3) they improve positive guidance since they are now also required to be centered over the lanes to which they apply.

[pianocello]

I haven't heard of any SPUIs being demolished and replaced with something else.

The SPUI at I-74 and 7th Avenue in Moline, IL, will be removed as part of the Mississippi River bridge replacement project.

This is true.  However, detailed study of the FEIS shows that the new crossing is being built substantially to the east of existing I-74, presumably to allow I-74 to remain open to traffic during construction.  The 7th Avenue SPUI is right at the point where the new alignment joins the new one, so it is not so surprising that the new configuration will not only not be a SPUI, but will also entail fairly indirect connections between I-74 and 7th Avenue for some movements, notably westbound 7th to southbound (book eastbound) I-74 and southbound I-74 to both directions of 7th.

Unfortunately, the SPUI is getting taken down, but at least the interchange will actually be for the through route (IL-92/4th and 6th Avenue) when all is said and done.

Back on-topic, I feel like the cloverleaf was one of the biggest fads in construction. Obviously, they're the best fit for a freeway-to-freeway junction in a rural area, but there used to be a lot of freeway-to-surface-street cloverleaves in urban and suburban areas (I-55 in Chicagoland, I-80 in Chicagoland before upgrades, I-74 in Peoria before 2006ish)-- Okay, this may have just been an Illinois thing, but it sure was popular.