California Observations

[Alps]

I know of no such study offhand, but the FHWA has considerable archives. I trust that the MUTCD has put considerable thought into its rulemaking.

Having had some experience with the MUTCD rulemaking process, it is evident to me that the research support for individual provisions of the MUTCD is uneven.  For example, the stippled-arrow diagrammatics (part of the MUTCD since the 1970's) were the result of a major study incorporating both tachistoscope work and real-world test signs (including the famous 70S/Democracy Blvd. sign).  In comparison, the recent addition of arrow-per-lane diagrammatics was based entirely on tachistoscope work.

Not really - Canada has used arrow-per-lane signs for a long time. If someone else has already done field tests, why duplicate?

The MUTCD also now has a fair number of warning signs whose research origin appears to be a synthesis of existing practice among state DOTs, which did not and was not intended to investigate the effectiveness of those signs (this is the same study that was eventually discovered by MTR denizens and found to have many unattributed road enthusiast photos).

Individual DOTs get to apply to try out certain symbol signs. Others, such as PA's "EXCEPT RIGHT TURN" under stop signs, are all-text and thus pass right by the FHWA trial process. In either case, only if they have success at the state level would they be applied Federally.

The FHWA MUTCD team has very good access to research work, including work done by state DOTs and universities which has not yet entered a formal publications process.  However, I am skeptical that there is a major study into exit tab design which is hidden from TRIS and similar search engines.

The early days of exit numbers were inside the sign - see Merritt Parkway, NJ Turnpike, PA Turnpike, and others. The exit number plaque at some point won out. I have to think that in the course of this evolution, something determined that the separate plaque is superior. Otherwise, why would everyone be changing?

It is certainly true that the MUTCD does specify that exit numbers should be put on a "separate plaque at the top of the Advance Guide or Exit Direction sign," but this language has not changed between the 2003 and 2009 editions of the MUTCD (in 2003 it appears at § 2E.28; in 2009 it appears at § 2E.31).  While the illustrations have invariably shown part-width tabs which are not part of the main sign panel, I see little evidence that this particular provision has ever been interpreted (either by FHWA or a state DOT) to prohibit full-width tabs which are structurally part of the main sign panel, as used in Illinois DOT District 1 and in Washington state.  It could even be argued (rather jesuitically) that the California bitten-out tabs comply since they are bordered overlays on one part of the sign panel (thus visually separate from the main panel legend) and their top edges coincide with the top edge of the sign.

Exit number plaques have a certain minimum width, one that will go up in the forthcoming Standard Highway Signs. However, there is nothing prohibiting full-width exit tabs to my offhand knowledge. I could go back and check if there's any "MAX" cap on certain clearances within the sign, but I'm pretty sure there aren't (or otherwise EXIT 1 would create a contradiction between MAXes and MINs). What is undeniably certain is that these are separate plaques, and therefore cannot be included in part of the other sign. And the shape of the other sign MUST be rectangular per the MUTCD, as must the shape of the exit number plaque. The California practice violates these requirements.

[NE2]

The early days of exit numbers were inside the sign - see Merritt Parkway, NJ Turnpike, PA Turnpike, and others. The exit number plaque at some point won out. I have to think that in the course of this evolution, something determined that the separate plaque is superior. Otherwise, why would everyone be changing?

To nitpick, early NJ Turnpike exits were on "tabs" at the bottom of the sign. Texas did something similar at the top: http://www.texasfreeway.com/Houston/historic/photos/images/i45_safety_barrier_july_1956.jpg

Have any photos been found of the early NYC parkway exit numbers from 1938?

[myosh_tino]

Exit number plaques have a certain minimum width, one that will go up in the forthcoming Standard Highway Signs. However, there is nothing prohibiting full-width exit tabs to my offhand knowledge. I could go back and check if there's any "MAX" cap on certain clearances within the sign, but I'm pretty sure there aren't (or otherwise EXIT 1 would create a contradiction between MAXes and MINs). What is undeniably certain is that these are separate plaques, and therefore cannot be included in part of the other sign. And the shape of the other sign MUST be rectangular per the MUTCD, as must the shape of the exit number plaque. The California practice violates these requirements.

If you are saying full width tabs like those used in Washington are OK, then may I present the following illustration...



If full width tabs are OK, then why would the California method of adding exit numbers shown above violate the FHWA MUTCD's requirements?  I will concede that the height of tab, the legend and numerals are undersized but I would argue that this particular California method is better than the WSDOT full width tab simply because the tab would be justified for a right or left exit.

[J N Winkler]

For example, the stippled-arrow diagrammatics (part of the MUTCD since the 1970's) were the result of a major study incorporating both tachistoscope work and real-world test signs (including the famous 70S/Democracy Blvd. sign).  In comparison, the recent addition of arrow-per-lane diagrammatics was based entirely on tachistoscope work.

Not really - Canada has used arrow-per-lane signs for a long time. If someone else has already done field tests, why duplicate?

Be specific.  Which Canadian province?  If you are talking about the option-lane diagrammatics which were introduced in Ontario around the time that province went bilingual (mid-1990's), then yes, those were based on a human-factors study Bob Dewar carried out (which I believe is now downloadable from the MTO Library website as a scanned PDF).  But the design criteria are different and the MUTCD makes no attempt to imitate Canadian practice as regards provision of these signs (for example, the Canadian signs don't attempt to get straight-ahead and exit information on the same sign panel).  I am not aware that the Katz tachistoscope study, which gave rise to the MUTCD arrow-per-lane diagrammatics, even cites Dewar's previous study.

The MUTCD also now has a fair number of warning signs whose research origin appears to be a synthesis of existing practice among state DOTs, which did not and was not intended to investigate the effectiveness of those signs (this is the same study that was eventually discovered by MTR denizens and found to have many unattributed road enthusiast photos).

Individual DOTs get to apply to try out certain symbol signs. Others, such as PA's "EXCEPT RIGHT TURN" under stop signs, are all-text and thus pass right by the FHWA trial process. In either case, only if they have success at the state level would they be applied Federally.

That synthesis study does not attempt to evaluate effectiveness.  It does note that the symbol signs use graphics not covered by the FHWA experimentation process.

The early days of exit numbers were inside the sign - see Merritt Parkway, NJ Turnpike, PA Turnpike, and others. The exit number plaque at some point won out. I have to think that in the course of this evolution, something determined that the separate plaque is superior. Otherwise, why would everyone be changing?

"Everyone" is not changing.  The British still have junction numbers toward the bottom left of the sign panel, well within the sign panel border.  Bottom placement of exit number information is also used in Sweden and Finland, albeit as structurally distinct tabs.  France puts exit numbering information on separate sign panels toward the top of signing assemblies, but these panels are the same width as the main sign panel, so the overall effect is similar to Washington state/Illinois DOT District 1.  Spain uses part-width exit number cartouches at the top which are however structurally part of the main sign panel and are not prominent as tabs because distance-to-exit is ranged to the left (for right exits) or to the right (for left exits).

So the contention that the separate part-width tab "won out" because it was superior does not survive scrutiny of international experience.  This is important because it suggests that any advantages of the vanilla MUTCD approach, compared to other approaches which are visually different but technically comply with the MUTCD verbiage, are slight at most.

I can think of many reasons agencies have chosen to adopt or not to adopt the vanilla MUTCD approach to tab placement and format, most having to do with substrate technology, sign mounting practices, and the perceived aesthetic felicity of equal-height sign panels.  You can expect to see plenty of strip-style tabs among agencies which use laminated sign panels (not just Caltrans, but also PennDOT); Caltrans uses bitten-out tabs because that style is most easily accommodated by formed panels in RSPFs; etc.  States which have gone for the vanilla MUTCD approach tend to use extruded aluminum or sheet aluminum with stiffeners combined with provision for securing structurally separate exit tabs to the stiffening assembly for the main sign panel.  Some Western states accomplish the same with plywood substrates for both tab and main sign panel.  In the US these approaches are very common (accounting, at a guess, for well over 80% of state DOTs) but are by no means universal.

What is undeniably certain is that these are separate plaques, and therefore cannot be included in part of the other sign. And the shape of the other sign MUST be rectangular per the MUTCD, as must the shape of the exit number plaque. The California practice violates these requirements.

You are assuming that this requirement entails structural separateness, and cannot be met by using overlays or a format which separates the exit number information from the main sign legend by one or more ruled lines.  I do not think it is the intent of the MUTCD authors to require this and, more importantly, I don't think FHWA would insist on such an interpretation in view of the cost implications for large state DOTs like Caltrans.

[Brandon]

If full width tabs are OK, then why would the California method of adding exit numbers shown above violate the FHWA MUTCD's requirements?  I will concede that the height of tab, the legend and numerals are undersized but I would argue that this particular California method is better than the WSDOT full width tab simply because the tab would be justified for a right or left exit.

Use Illinois's and Michigan's method for full width tabs.  These are right or left aligned with the side the exit ramp is on.

[Alps]

Exit number plaques have a certain minimum width, one that will go up in the forthcoming Standard Highway Signs. However, there is nothing prohibiting full-width exit tabs to my offhand knowledge. I could go back and check if there's any "MAX" cap on certain clearances within the sign, but I'm pretty sure there aren't (or otherwise EXIT 1 would create a contradiction between MAXes and MINs). What is undeniably certain is that these are separate plaques, and therefore cannot be included in part of the other sign. And the shape of the other sign MUST be rectangular per the MUTCD, as must the shape of the exit number plaque. The California practice violates these requirements.

If you are saying full width tabs like those used in Washington are OK, then may I present the following illustration...



If full width tabs are OK, then why would the California method of adding exit numbers shown above violate the FHWA MUTCD's requirements?  I will concede that the height of tab, the legend and numerals are undersized but I would argue that this particular California method is better than the WSDOT full width tab simply because the tab would be justified for a right or left exit.

The one on the right is noncompliant because the border is required to be at the edge of the sign. The one on the left is noncompliant because the exit number is centered instead of right-justified. Both should have Type A arrows instead of Type B.

[myosh_tino]

Both should have Type A arrows instead of Type B.

Is that a FHWA MUTCD requirement or is it a recommendation?  California uses the Type A (longer shaft) arrows only if there are two lines of text like this...


The shorter shaft Type B arrows are used when there is only one line of text or if the arrows appear at the bottom of the sign.  Examples...




FWIW, that WSDOT sign I drew is based on the actual sign found on I-5 in Vancouver, WA...

From the AARoads Gallery.

Also, I do believe Nevada uses the shorter shaft Type B arrows extensively on guide signs.

[Alps]

Both should have Type A arrows instead of Type B.

Is that a FHWA MUTCD requirement or is it a recommendation?  California uses the Type A (longer shaft) arrows only if there are two lines of text like this...

The shorter shaft Type B arrows are used when there is only one line of text or if the arrows appear at the bottom of the sign.

Also, I do believe Nevada uses the shorter shaft Type B arrows extensively on guide signs.

The MUTCD has guidelines for one or the other - yes, one-line signs can have Type B, but my general rule is, if the sign design allows a Type A without adding to the sign size, use a Type A. Type B should be reserved for constrained signs, especially ground-mounts, because it's a stubbier looking arrow that can be harder to make out from a distance. That said, it's not a critical error.

[myosh_tino]

The one on the right is noncompliant because the border is required to be at the edge of the sign. The one on the left is noncompliant because the exit number is centered instead of right-justified.

So if California went with full-width tabs but justified the exit number like this...

...that would be OK in your opinion?

How about this...

The only difference is the additional horizontal vertical line that sort of forms a "tab" for the exit number.  This sign was one of the first ones installed in the state to kick off the exit numbering project.

[roadfro]

Both should have Type A arrows instead of Type B.

Is that a FHWA MUTCD requirement or is it a recommendation?
(...)
Also, I do believe Nevada uses the shorter shaft Type B arrows extensively on guide signs.

Nevada only uses the shorter Type B arrow for arrows found on the bottom of a sign. Generally, these are on exit direction signs of multi-lane exits, or on guidance signs on ramp terminals and approaching interchanges where there is an arrow per lane for guidance.

[Brandon]

The one on the right is noncompliant because the border is required to be at the edge of the sign. The one on the left is noncompliant because the exit number is centered instead of right-justified.

So if California went with full-width tabs but justified the exit number like this...

...that would be OK in your opinion?

How about this...
{Image}
The only difference is the additional horizontal line that sort of forms a "tab" for the exit number.  This sign was one of the first ones installed in the state to kick off the exit numbering project.

Actually, your drawing looks great.  That is exactly what we use here in IDOT District 1 (which tends to make the signs the same height across the sign bridge).  Now if CalTrans can just remove that unsightly vertical line...

An IDOT example:

[blawp]

It seems to me that a lot of people just like to pick on California and the way things are done here, despite the fact our methods are typically no better or worse than most other places.

Sure, we might do exit tabs funny. I don't call out most of the rest of the nation for using span wire signals with no backplates and incandescent luminaries, or that no other state puts staggered loop detection at all signalized intersections on the major and minor approaches like we do to minimize the yellow light trap.

And, in general, our freeway landscaping is far superior to other states'.

[brad2971]

It seems to me that a lot of people just like to pick on California and the way things are done here, despite the fact our methods are typically no better or worse than most other places.

Sure, we might do exit tabs funny. I don't call out most of the rest of the nation for using span wire signals with no backplates and incandescent luminaries, or that no other state puts staggered loop detection at all signalized intersections on the major and minor approaches like we do to minimize the yellow light trap.

And, in general, our freeway landscaping is far superior to other states'.

I don't have a problem with the way exit tabs are done by Caltrans. The process makes better use of the entire sign panel, which should be helpful should Caltrans ever decide to test-drive Clearview on its signs (San Diego will be the guinea pig on this one).

[Interstate Trav]

It seems to me that a lot of people just like to pick on California and the way things are done here, despite the fact our methods are typically no better or worse than most other places.

Sure, we might do exit tabs funny. I don't call out most of the rest of the nation for using span wire signals with no backplates and incandescent luminaries, or that no other state puts staggered loop detection at all signalized intersections on the major and minor approaches like we do to minimize the yellow light trap.

And, in general, our freeway landscaping is far superior to other states'.

I completely agree with ywhat your saying.

[andy3175]

@brad2971 ... how have you learned that Clearview will be test-driven in San Diego? While I know Caltrans has approval to use the font, I'd not seen anything indicating a planned roll out for usage. A link or reference would be helpful!

Thanks,
Andy

[brad2971]

@brad2971 ... how have you learned that Clearview will be test-driven in San Diego? While I know Caltrans has approval to use the font, I'd not seen anything indicating a planned roll out for usage. A link or reference would be helpful!

Thanks,
Andy

I've never seen any plans to go to Clearview in CA. I'm just...taking a guess

[myosh_tino]

The process makes better use of the entire sign panel, which should be helpful should Caltrans ever decide to test-drive Clearview on its signs (San Diego will be the guinea pig on this one).

Oh dear god, I DO NOT want to see signs that might look like this popping up in California...

[Alps]

The one on the right is noncompliant because the border is required to be at the edge of the sign. The one on the left is noncompliant because the exit number is centered instead of right-justified.

So if California went with full-width tabs but justified the exit number like this...

...that would be OK in your opinion?

How about this...

The only difference is the additional horizontal vertical line that sort of forms a "tab" for the exit number.  This sign was one of the first ones installed in the state to kick off the exit numbering project.

Interesting. I suppose I can't find fault with the second one because the border does go all the way around. So, yes, both would be okay.

[jrouse]

As I have a said a number of times, California's reasoning for putting the exit tab inside the sign panel was due to existing wind-loading requirements that precluded Caltrans from using "regular" tabs.  Simply put, the sign structures (sign bridges, mounting hardware, etc) cannot handle external tabs as currently designed.  I read somewhere that Caltrans has developed or updated some of this hardware to accommodate external tabs but I suspect existing hardware is going to be used until the supply has been exhausted.  Perhaps, jrouse can clarify this issue as he is a Caltrans employee.

Sorry, just logged onto here after a few weeks' absence and saw this.   

The Caltrans sign truss standards were significantly revised in early 2005.  At that time, it was noted that the new structures could accommodate exit number tabs.  However, to this day, there has not been a detail made available for mounting tabs.  I have spoken with the engineer who is responsible for the sign structure standard plans, and he has told me that he knows there is a need for such a detail, but it is not a high priority.

I have the plan sheets for the 1971 exit numbering experiment in San Diego.  It shows mounting details for the tabs for different types of sign structures.  I don't see why those details could not be incorporated onto a 2005 truss structure.  But that's just me...there may be more to it.

[ARMOURERERIC]

Fear not on the clearview in San Diego.  I was on WB I-8, and new overheads for CA 125 have been installed for both the exit split and the advance signage.  It is well done, neat, consistant and uses the standard fonts.

[KEK Inc.]

Any pictures of the Clearview in California?  I know some cities are using them, but I have yet to see a BGS with one.

[CentralCAroadgeek]

I noticed one Clearview sign last summer in the Inland Empire. It is a truck scales sign located along I-10 east between Banning and Cabazon.

I unfortunately didn't take a picture, so here's the GSV image.

[Bigmikelakers]

Any pictures of the Clearview in California?  I know some cities are using them, but I have yet to see a BGS with one.

Here's one of the few clearview signs in California. I'm sure ADOT probably installed this one though.


Interstate 10 Eastbound and US 95 Southbound in Blythe by bigmikelakers, on Flickr

[agentsteel53]

I'm sure ADOT probably installed this one though.

you are correct.  the sign is completely made to Arizona standards.

that said, on the Arizona side approaching the Blythe exits in California ... those are Arizona signs too!

[pctech]

How does Caltrans handle the "embedded" exit number tab with a left handed exit? In most states(that I've been to) a left exit number tab is labeled as "left exit" and has a yellow background with black lettering, similar to "exit only" labels.
I just joined the forum, hope to learn more about how roads/highways are designed/built etc.

Thanks