Do any engineers here favor Clearview?

[mcmc]

It's no secret that Clearview is unpopular among roadgeeks (to put it mildly). Clearview's advocates--academics and DOT types--however, cite its technical advantages over FHWA. There are plenty of engineers on here. Do any of you favor Clearview--and why?

I'm eager to see someone play the devil's advocate.

[cpzilliacus]

It's no secret that Clearview is unpopular among roadgeeks (to put it mildly). Clearview's advocates--academics and DOT types--however, cite its technical advantages over FHWA. There are plenty of engineers on here. Do any of you favor Clearview--and why?

I'm eager to see someone play the devil's advocate.

I work as an engineer, though my formal education is in IT/CS - I am definitely not a P.E.

But the research work that was done on Clearview was pretty compelling (from what I have read, its development was influenced by human factors studies and engineering, which I did study in college).

I don't consider Clearview to be especially less-attractive than the "traditional" FHWA fonts, or, for that matter, the official highway sign font in Sweden (Tratex) or one used in the U.K. (Transport) or the one in Finland (a commercial "clone" version is out there called Helsinki, though that is not what Finnish highway engineers call it).

[Alps]

I'm an engineer, and I believe that using Series E instead of E(M) would have made a big difference in the comparison tests. I'm not sold on Clearview until it's fairly compared with an FHWA variant with a similar stroke width. I think the shapes of the FHWA letters are not just more aesthetic, but easier to distinguish. Georgia's mixed-case D beats the snot out of anything Clearview can attempt.

[DaBigE]

I am a licensed PE, and I am not in favor of Clearview, at least not until further testing is done. As somewhat eluded to by Steve, I don't think enough testing was done with various configurations of the existing FHWA fonts. I still believe that changing to Series E or D, while retaining current letter height specs would have had the same (or better) effect than switching to Clearview. Taking off my engineer hat and just as Joe Taxpayer, IMHO, Clearview was a misappropriated use of monies, especially given the large holes left by not thorough enough testing (read: it was rushed to market).

On the other hand, my boss is a big advocate of Clearview and seems to love that flavor of Kool Aid. We've had some interesting discussions on the issue in the past. He understands my standpoint and the states that have banished Clearview, (Wisconsin, cough, cough), but remains a firm believer in it.

In any case, I especially do not like the high costs of obtaining the fonts.

[J N Winkler]

A few observations (from a technically trained non-engineer):

*  I believe one of the first TTI studies dealing with Clearview compared it with Transport Medium and FHWA Series E, with Series E falling in the middle of the pack.

*  Georgia DOT has now abandoned mixed-case Series D on freeway guide signs, in favor of the Series E Modified that had been used previously.

*  It is surprisingly common for the engineers I have seen commenting on this issue here and on MTR to take a stand that is at variance with the engineering policy decisions of their state DOT employers regarding Clearview.

I don't think there is a legibility bonanza to be had from tinkering with the stroke width or even the uppercase/lowercase ratio of the FHWA alphabet series to counter Clearview's advantages against microprismatic backgrounds.  The difference in stroke width between Clearview 5-W and FHWA Series E Modified is actually pretty small:  Clearview gains in legibility not because it uses a thinner stroke, but because the stroke width varies (it is a humanist typeface), and because the counters are bigger, which is possible because the ratio of lowercase loop height to capital letter height is larger than for FHWA Series E Modified.

The experience of the last ten years has shown that FHWA Series E Modified can hold its own against Clearview because the latter offers an increase in reading distance of only about 10% when sign surface area is held constant, which is less than the size step increment at typical freeway speeds (20" UC versus 16" UC, which is an increase of 25%).  As a result, Clearview has not broken through and adoption among the state DOTs has more or less stalled.  This is not Griliches and the hybrid corn; this is just another purported better mousetrap which couldn't live up to the hype.

[PHLBOS]

I'm an engineer, and I believe that using Series E instead of E(M) would have made a big difference in the comparison tests. I'm not sold on Clearview until it's fairly compared with an FHWA variant with a similar stroke width. I think the shapes of the FHWA letters are not just more aesthetic, but easier to distinguish. Georgia's mixed-case D beats the snot out of anything Clearview can attempt.

I am a licensed PE, and I am not in favor of Clearview, at least not until further testing is done. As somewhat eluded to by Steve, I don't think enough testing was done with various configurations of the existing FHWA fonts. I still believe that changing to Series E or D, while retaining current letter height specs would have had the same (or better) effect than switching to Clearview. Taking off my engineer hat and just as Joe Taxpayer, IMHO, Clearview was a misappropriated use of monies, especially given the large holes left by not thorough enough testing (read: it was rushed to market).

On the other hand, my boss is a big advocate of Clearview and seems to love that flavor of Kool Aid. We've had some interesting discussions on the issue in the past. He understands my standpoint and the states that have banished Clearview, (Wisconsin, cough, cough), but remains a firm believer in it.

In any case, I especially do not like the high costs of obtaining the fonts.

Agree with both of you 100% and I am a P.E. BTW.

[cpzilliacus]

I am a licensed PE, and I am not in favor of Clearview, at least not until further testing is done. As somewhat eluded to by Steve, I don't think enough testing was done with various configurations of the existing FHWA fonts. I still believe that changing to Series E or D, while retaining current letter height specs would have had the same (or better) effect than switching to Clearview. Taking off my engineer hat and just as Joe Taxpayer, IMHO, Clearview was a misappropriated use of monies, especially given the large holes left by not thorough enough testing (read: it was rushed to market).

How much testing is enough testing?  I ask that in a rhetorical sense.

From what I have heard at TRB Annual Meeting sessions, Clearview was extensively tested, and found to be better, especially for people with less than 20/20 vision.  And the U.S. population is aging. 

Note that while I like Clearview, I also like some other "highway" fonts (including the various traditional "FHWA Gothic" fonts), as stated above, and am not an "evangelist" for any of them.

I think it's also important to mention that Clearview is not approved by the FHWA for negative-contrast use (dark characters on a light background).

On the other hand, my boss is a big advocate of Clearview and seems to love that flavor of Kool Aid. We've had some interesting discussions on the issue in the past. He understands my standpoint and the states that have banished Clearview, (Wisconsin, cough, cough), but remains a firm believer in it.

Can you share why he likes it?  I ask out of curiosity.

In any case, I especially do not like the high costs of obtaining the fonts.

That is an excellent point.

[DaBigE]

From what I have heard at TRB Annual Meeting sessions, Clearview was extensively tested, and found to be better, especially for people with less than 20/20 vision.  And the U.S. population is aging.

Not to completely change topics, but how much age-related accommodation should we be considering in our designs? Signs can only grow so large before they become cost prohibitive. At least in for the short-term, changing fonts is not cheap when you factor in the costs of obtaining the fonts and labor to change detail drawings. Depending on the state, that can be a lot of manhours.

Some may see it as being crass, but a "benefit" to maintaining the status-quo is it gives a definitive point to tell drivers they may not have the skills to safely operate a vehicle any longer (or, at the very least, to get their eyes checked). It's a tough call to make, but it needs to be made.

On the other hand, my boss is a big advocate of Clearview and seems to love that flavor of Kool Aid. We've had some interesting discussions on the issue in the past. He understands my standpoint and the states that have banished Clearview, (Wisconsin, cough, cough), but remains a firm believer in it.

Can you share why he likes it?  I ask out of curiosity.

Basically, he finds it easier to read, mainly because of the thinner stroke width. He does agree that more could have been tested with variations of the FHWA fonts before creating a completely new font.

[PHLBOS]

I think it's also important to mention that Clearview is not approved by the FHWA for negative-contrast use (dark characters on a light background).

Tell that to both PTC and PennDOT; many of their light background signs have been Clearview for quite a few years.  Of the 2 agencies, the PTC is by far the worst offender in this category.

[1995hoo]

I think it's also important to mention that Clearview is not approved by the FHWA for negative-contrast use (dark characters on a light background).

Tell that to both PTC and PennDOT; many of their light background signs have been Clearview for quite a few years.  Of the 2 agencies, the PTC is by far the worst offender in this category.

Come to Virginia. Several of the signs shown on the FHWA's Clearview FAQ site as examples of incorrect Clearview implementation are VDOT signs that I pass almost every day. Come to think of it, I think I passed at least three relatively new–posted within the past month–negative-contrast Clearview signs this morning (two black-on-yellow and a black-on-white, all of them in all-caps as well).

I'm not an engineer and so have no comment on the original topic. I do find Clearview easier to read at a distance, though.

[Takumi]

^ VDOT also uses it in exit tabs a lot, an application which I believe is not approved, as well as gore signs, about which I'm not sure.

[J N Winkler]

At least in for the short-term, changing fonts is not cheap when you factor in the costs of obtaining the fonts and labor to change detail drawings. Depending on the state, that can be a lot of manhours.

The argument that Clearview is more expensive needs further illumination.  Is it really that much more expensive to purchase a complete set of the Clearview fonts than a copy of the FHWA Series fonts?  How does the cost vary by sign design package used, and how are the licensing arrangements structured?

The cost I have heard is about $700 for a workstation license for a full set of Clearview fonts, which is quite small compared not just to the total cost of a sign replacement contract, but also a licensed copy of SignCAD (around $2000, I think).  And if the license is nonexpiring, then it is essentially a one-time expense.  Meanwhile, professional-quality font renditions of the FHWA alphabet series themselves are not free, though the glyphs are in the public domain.

Not to completely change topics, but how much age-related accommodation should we be considering in our designs? Signs can only grow so large before they become cost prohibitive.  [. . .]  Some may see it as being crass, but a "benefit" to maintaining the status-quo is it gives a definitive point to tell drivers they may not have the skills to safely operate a vehicle any longer (or, at the very least, to get their eyes checked). It's a tough call to make, but it needs to be made.

It is reasonable to pay more to accommodate aging drivers up to the point that the benefits to society arising from such accommodations are outweighed by the costs.  It is a conceptually straightforward cost-benefit calculation, although in practice it is somewhat complicated by the need to use hedonic pricing for some variables, such as any increases in crashes that are a potential downside of older drivers negotiating a highway network that is not completely adapted to their needs.

I would not want to sit before a committee in the state legislature and try to argue that my state DOT employer should stick with an (arguably) technically inferior traffic sign typeface just to give older drivers a clear signal that their skills are no longer adequate for negotiating the highway infrastructure.  It is much safer to argue that the benefits are sufficiently limited that switching costs and quality assurance problems are adequate reasons not to change over to Clearview.

[cu2010]

I think it's also important to mention that Clearview is not approved by the FHWA for negative-contrast use (dark characters on a light background).

Tell that to both PTC and PennDOT; many of their light background signs have been Clearview for quite a few years.  Of the 2 agencies, the PTC is by far the worst offender in this category.

NYSTA is a pretty bad offender too...they just love slapping Clearview on everything. And I mean everything.

Add to that the fact that they're terrible at using it properly, leading to butt-ugly signs...ugh.

[1995hoo]

^ VDOT also uses it in exit tabs a lot, an application which I believe is not approved, as well as gore signs, about which I'm not sure.

It's not approved for gore signs that use numbers because the FHWA's guidance says words in all-caps, and numerals, are supposed to be in the old typefaces. Because a gore sign has "EXIT" in all-caps, and often a number following underneath, it would violate the guidelines (boldface in original):

Q: Since Clearview is so much more legible than the old highway lettering, and it was based on using upper— and lower-case letters, should I now display all lettering on signs using upper- and lower-case letters as I've seen illustrated in some documents?

A: Mixed-case legends are restricted to place names and destinations; all other messages such as action and distance messages, cardinal directions, and auxiliary designations shall remain composed of all upper-case letters employing the the MUTCD criteria. Legends composed of all upper-case letters did not demonstrate a like improvement over the Standard Alphabets when displayed using Clearview. Accordingly, words composed of all upper-case letters continue to use the Standard Alphabets.

Q: Does this mean all letters, numerals, and characters of Clearview are significantly more legible?

A: Numerals and special characters have not been tested for legibility and concerns have been reported thereon in field applications. Therefore, numerals continue to be displayed on highway signs using the Standard Alphabets.


Figure 4. ACCEPTABLE: Example of appropriate use of Clearview for destination legend (mixed-case) and FHWA Standard Alphabets for other legends (all upper-case and numerals).

Incidentally, regarding "words composed of all upper-case letters," Figure 5a on that page shows one of VDOT's "bad-Clearview" signs on I-395. They're citing it as "unacceptable" because the fraction was done incorrectly, but it happens to include the word "MILE" in all-caps as well.

Source for the above: "Design and Use Policy for Clearview Alphabet" from the MUTCD site

[DaBigE]

At least in for the short-term, changing fonts is not cheap when you factor in the costs of obtaining the fonts and labor to change detail drawings. Depending on the state, that can be a lot of manhours.

The argument that Clearview is more expensive needs further illumination.  Is it really that much more expensive to purchase a complete set of the Clearview fonts than a copy of the FHWA Series fonts?  How does the cost vary by sign design package used, and how are the licensing arrangements structured?

The cost I have heard is about $700 for a workstation license for a full set of Clearview fonts, which is quite small compared not just to the total cost of a sign replacement contract, but also a licensed copy of SignCAD (around $2000, I think).  And if the license is nonexpiring, then it is essentially a one-time expense.  Meanwhile, professional-quality font renditions of the FHWA alphabet series themselves are not free, though the glyphs are in the public domain.

Except that what you describe is for an agency starting from scratch. New fonts can be plugged into most existing software packages. Retaining current designs/fonts has zero additional cost. For many agencies that design their own signs, they already have the full set of FHWA fonts. Similarly, many existing agencies have, in some cases, hundreds of individual sign plate detail sheets that would require upgrading, in addition to comprehensive sign layouts that require upgrading. As much as FHWA would like to believe, not all agencies copy and paste their standard sign layouts.

I would not want to sit before a committee in the state legislature and try to argue that my state DOT employer should stick with an (arguably) technically inferior traffic sign typeface just to give older drivers a clear signal that their skills are no longer adequate for negotiating the highway infrastructure.  It is much safer to argue that the benefits are sufficiently limited that switching costs and quality assurance problems are adequate reasons not to change over to Clearview.

Sorry, I should have explained my point a little better. I didn't mean for a sign font being the end-all, be-all criterion for pulling unsafe drivers off the road. I have been a firm believer that states should have mandatory re-testing above a determined age (TBD by medical professionals). Frankly, I am appalled that my home state chose to renew licenses for eight years at a time. Once a person gets into their 60s and 70s, skills can change dramatically in a fraction of that time. "Helps older drivers" is an agrument I've heard time and time again, and not just in the case for Clearview fonts. At some point, we're making the roads more hazardous for other drivers by allowing people to remain on the road that should have turned in their keys years earlier. But that's another topic for another thread.

If the current fonts are so inferior, why wasn't this brought up decades ago? This is one place where I have to tip my hat to the U.K. Sign design is a science and not a popularity contest/political. Their sign design manuals are an interesting read for those who haven't seen them before.

[Quillz]

I don't really have a problem with Clearview. I don't think it looks that bad. I think for me, it looks awkward because I'm so used to the FHWA series. But I think had the two been reversed, ie the FHWA series was coming in to replace the decades old Clearview, I'd not like the former as much.

There is certainly a lot of research that suggests Clearview is better, at least when it comes to positive contrast signage.

[J N Winkler]

Except that what you describe is for an agency starting from scratch. New fonts can be plugged into most existing software packages. Retaining current designs/fonts has zero additional cost. For many agencies that design their own signs, they already have the full set of FHWA fonts. Similarly, many existing agencies have, in some cases, hundreds of individual sign plate detail sheets that would require upgrading, in addition to comprehensive sign layouts that require upgrading. As much as FHWA would like to believe, not all agencies copy and paste their standard sign layouts.

But the majority of standard sign plates are for negative-contrast signs, for which Clearview is not permitted and should not be used, so if an agency wanted to convert to Clearview as its primary typeface for guide signage, there would be only a fairly small number of standard sign plates to redo--mostly rest area signs, boundary/feature signs, certain types of tourist signs, and D-series signs:  probably fewer than 50 in all.  I could see Clearview resulting in a fresh need to re-do large numbers of sign designs only if the agency's routine practice was otherwise to "carbon-copy" designable signs through sign replacement cycles (i.e., use a given CAD design for one replacement in one year, and then re-use the exact same CAD design for the next replacement 20 years later).

For reasons of version stability, I think there are very few state DOTs that can do this.  WisDOT might be able to do it with its homegrown signing CAD bolt-on, and MnDOT might have been able to do it if it were still using its old Fortran-based sign design program, but I understand SignCAD has little version stability.  SignCAD-generated sign designs look different according to the version of the signcad.rsc file that is loaded into the MicroStation workspace.

This is aside from the fact that most state DOTs don't carbon-copy existing signs (and indeed deprecate the practice).  For example, I-19 in Arizona has not been upgraded aside from a few interchanges near Tucson since it was finished in the 1970's, but the signing has changed considerably, partly because Arizona DOT decided to drop city information from advance guide signs in the 1998 sign replacement (in the previous cycle, in 1981, Arizona DOT had put both street and city names on the advance guide signs).

Sorry, I should have explained my point a little better. I didn't mean for a sign font being the end-all, be-all criterion for pulling unsafe drivers off the road. I have been a firm believer that states should have mandatory re-testing above a determined age (TBD by medical professionals). Frankly, I am appalled that my home state chose to renew licenses for eight years at a time. Once a person gets into their 60s and 70s, skills can change dramatically in a fraction of that time. "Helps older drivers" is an agrument I've heard time and time again, and not just in the case for Clearview fonts. At some point, we're making the roads more hazardous for other drivers by allowing people to remain on the road that should have turned in their keys years earlier.

My point was really about presentation.  I don't disagree that there is an argument in favor of refraining from sending older drivers false signals that the highway infrastructure has been comprehensively redeveloped to meet their needs.  The problem is that this view needs to be expressed carefully, otherwise it comes across as "Let them eat cake."

There are significant collateral costs to taking the decision to continue driving out of older drivers' hands.  Since they lose mobility immediately, they become customers for a subsidized paratransit system, and they can also be forced to move into assisted living, which causes morbidity to go way up.  The added costs of re-testing and administrative surveillance for older drivers are also a significant burden on driver licensing systems which already struggle to meet basic expectations for customer service.

Society is considerably less out-of-pocket when it allows older drivers to use their greater emotional maturity, experience of life changes, and more precise understanding of their own capabilities to decide how to limit their driving and, if and when the need arises, to surrender their driver's licenses.  The costs are incurred only when such drivers make errors in judging their own capabilities, as is a problem to some extent for all age groups, not just senior citizens.

These factors do not absolutely prevent the state taking a greater role in deciding when older drivers must stop driving, but they do mean that any proposed change has to be carefully considered as to costs and benefits.

If the current fonts are so inferior, why wasn't this brought up decades ago? This is one place where I have to tip my hat to the U.K. Sign design is a science and not a popularity contest/political. Their sign design manuals are an interesting read for those who haven't seen them before.

The current FHWA alphabet series are research-led.  Once they were adopted, their legibility characteristics were accepted as a baseline for design purposes, and other design criteria for signs were structured around them.  This, however, did not mean that a better mousetrap could not be invented years or decades down the road (an observation which, by the way, also applies to Clearview).  The legibility performance of the typefaces was never controversial until the traffic research community started looking for ways in the late 1980's to provide for the demographic bulge of older drivers that is coming as the baby boomers age.  The research effort that spawned Clearview originally began with a study (I think by McGee) which suggested that the standard letter size for freeway guide signs would have to be increased from 16" UC to 20" UC to accommodate older drivers at some point in the future.  This was considered unaffordable and technically difficult, so tinkering with the intrinsic legibility of the standard typeface seemed like the most fruitful direction for further research.

In Britain, the legibility characteristics of the Transport typefaces have been subsumed into general design criteria for signs and are uncontroversial because Britain has no great demographic bulge of older drivers to cater for.  There is therefore no Clearview debate in Britain.  Driver licensing arrangements are also different--instead of periodic renewals at fixed intervals as in the US (which arguably can no longer be justified since license renewal is no longer used to administer refresher written tests), the license is valid until age 70 (though photocards need to be renewed every 10 years--a process which is normally handled by mail), at which point refresher written and driving tests become necessary at fairly short intervals.  In urban Britain it is much easier for elderly people to get around without a car and without having to resort to specialized and expensive paratransit services.  With free medical care for everybody, the typical elderly Briton is much more healthy and active than the typical elderly American to begin with.  The typical American scenario--older driver still on the road in his own car because public transit alternatives just aren't viable--is almost unknown outside the thinly populated Scottish Highlands.

I have some familiarity with the development of the current British signing system and, although it is in some respects more well-thought-out than ours, its development has not been altogether free of beauty-contest politics.  Background colors for direction signs were chosen largely on the basis of personal taste, as filtered through the Worboys committee.  Red slashes were eliminated from prohibitory roundels (contrary to the recommendations of the Worboys report) even though research later showed that the red slashes improved comprehension.  Adoption of the Worboys signs themselves entailed a massive conversion from word-message to symbolic signs--again, research showed that sign comprehension went down.  Our three-destination (exceptionally four-destination) limit for D-series signs is based on design criteria fixed by Forbes in a couple of studies in the late 1930's and early 1940's; Britain has a six-destination limit, which is based on a different theory of sign reading (which requires only that drivers be able to pick out the destination they are looking for) and is arguably less conservative than ours.

A major argument against the adoption of Clearview in the US is that it is too easy for inexperienced or naïve sign designers to make mistakes with it.  This problem is far worse in Britain, where sign designers have to observe a multiplicity of very precise rules and keep constantly in mind a far greater array of basic design concepts.  Over time and with the casualization of employment in design offices, this has led to so many quality assurance problems that a major head of investigation in the last traffic signing review was simplification of the design rules so that they can be applied consistently and accurately by relatively unskilled personnel.

[Roadsguy]

If that sign is where I think it is, then I just passed it yesterday (maybe today).

Lemme guess, somewhere on I-81 in PA.

[mcmc]

If so many engineers are indeed against Clearview, why hasn't there been a backlash among the professionals the various DOTs?

Adoption of Clearview has always been optional--and even then for very limited uses (mixed-case use on guide signs). Its usage, generally, has been adopted far beyond its approved uses (exit signs, tabs, all caps usages, etc.). Why the headlong rush--and virtually no ensuing backlash? Clearview is still only approved for "interim" usage. Is there any chance of stopping Clearview's march?

[Scott5114]

FHWA didn't add Clearview to the 2009 MUTCD. I think that speaks to FHWA, while not outright rejecting it (yet), not being quite sold on it yet. They could very well at some point decide to yank the interim approval, forcing everyone to go back the FHWA Series fonts (unless they spend no federal money on them).

[J N Winkler]

If so many engineers are indeed against Clearview, why hasn't there been a backlash among the professionals the various DOTs?

There has been.  Massachusetts' MUTCD supplement now actively forbids the use of Clearview in the state.  Some other state DOTs (e.g., WisDOT) have carried out localized experiments with Clearview and decided to stick with Series E Modified.  Meanwhile, still others (e.g., Arizona DOT) were enthusiastic initial adopters of Clearview but have come to see that there are problems with aspects of it, such as digits that are hard to read, and have pruned their usage accordingly.

My judgment, speaking as one who has been collecting pattern-accurate sign design sheets from various state DOTs over the years, is that Clearview adoption has already passed its high-water mark.

Adoption of Clearview has always been optional--and even then for very limited uses (mixed-case use on guide signs). Its usage, generally, has been adopted far beyond its approved uses (exit signs, tabs, all caps usages, etc.). Why the headlong rush--and virtually no ensuing backlash? Clearview is still only approved for "interim" usage. Is there any chance of stopping Clearview's march?

Regarding the last two sentences, see above.  In regard to all-uppercase legend on signs:  FHWA's interim approval for Clearview does not actually forbid the use of Clearview all-caps in positive contrast, or the use of Clearview typefaces other than 5-W and 5-W-R.  It is actually the Clearview FAQ on the MUTCD website, a separate document with no regulatory value which came out much later, which deprecates the use of Clearview typefaces other than 5-W and 5-W-R, the use of Clearview on non-designable signs even in positive contrast (e.g., the Interstate route marker), and the use of Clearview for all-caps legend even in positive contrast.

Negative-contrast Clearview has never been approved by FHWA.  Its usage is an indication of quality assurance problems in traffic design offices.  Remember that in sign design software, Clearview remains equally accessible to the user regardless of whether it is being applied in positive or negative contrast, and a sign design on a plan sheet nearly always appears as black letters or keylines against a white background, regardless of whether the actual sign is positive or negative contrast.

If a careless or poorly trained designer uses Clearview for a negative-contrast sign, and the engineer does not take the time to review the design carefully before he applies his seal (or other mark of approval) to the plan sheet, then the contractor takes on an obligation to fabricate and erect the sign to the erroneous design when the project is put out to bid and awarded.

[J N Winkler]

They could very well at some point decide to yank the interim approval, forcing everyone to go back the FHWA Series fonts (unless they spend no federal money on them).

They could indeed do that, but Clearview has been rolled out in so many states at this point that I think FHWA is unlikely to mandate its immediate removal--I think the more likely scenario is a phaseout program coordinated with AASHTO.  Clearview could easily be removed in the same gradual fashion as button copy and old "house style" signs in states which had their own custom typefaces.

[vdeane]

I don't see them ever forcing states to remove it, but forcing new sings to be FHWA is what they would likely do if the interim approval were removed.

[mcmc]

What are the real chances that interim approval will be revoked? And what about the opposite outcome: that Clearview will get permanent approval--perhaps even favored status over the FHWA series?

[Scott5114]

What are the real chances that interim approval will be revoked? And what about the opposite outcome: that Clearview will get permanent approval--perhaps even favored status over the FHWA series?

I dunno. It depends on how FHWA feels about it.  Judging by that page that FHWA has up about improper use of Clearview, there are only limited circumstances where the font has any advantage at all. FHWA might judge that those limited benefits aren't enough to mandate Clearview. They will have to mandate one or the other at some point; I don't see the two coexisting in the SHS at any point. And considering the mandate hasn't gone to Clearview yet...