Pushing the MUTCD envelope: arrow-per-lane diagrammatics

[J N Winkler]

From a recent Georgia DOT sign rehabilitation contract covering I-75 in Atlanta (GDOT is in the middle of a multi-year freeway sign upgrade program to get rid of Series D/"GDOT Turkish" for primary destination legend):

[SidS1045]

Apparently Massachusetts will begin using arrow-per-lane designs soon.  From the MA supplement to the 2009 MUTCD:

Section 2E.20 Signing for Option Lanes at Splits and Multi-Lane Exits
At present, "Arrow Per Lane"  guide signs are not being specified for use on highways within
Massachusetts in order to maintain consistency in sign messages at "optional lane"  interchanges on
the freeway system, given the large number of existing "conventional"  diagrammatic signs currently
in place.

NOTE: The Department will be phasing in the "Arrow Per Lane"  design, within the next ten to
fifteen years, along specific highway corridors as signs are updated during normal replacement. In
the interim, the support structures for any new "conventional"  diagrammatic sign installations at
these locations will be designed to accommodate future upgrading to the larger "Arrow Per Lane"
signs.

[Revive 755]

Why does the leftmost sign on the first sheet need arrows anyway?  A pull through with just the control cities would be fine.

[myosh_tino]

I was in the process of drawing the signs in JN Winkler's post when I realized that there are no option lanes in either of the two situations.  IIRC, the arrow-per-lane signs were only supposed to be used if there was an option lane as part of the upcoming exit.  Also, according to my calculations, the up arrows on the I-75/I-85 pull through are only 48 inches high versus the specified 72 inches.

[Eth]

Another new sign for the 75/85 split already? That one was just replaced a couple years ago, new enough to be Series E(M) and everything. And that's without even going into the ludicrousness of having a single BGS spanning 6+ lanes.

[roadman]

Unless I'm missing something, there's a problem here.  Georgia's proposed "arrow per lane" BGSes don't depict any 'optional' exit lanes - which is the only configuration these signs are supposed to be used for.

Plus, these signs illustrate a basic problem with the "arrow per lane" design - they are unnecessarily large for the message they convey.  And, if 'arrow per lane' signs are really so much better than the diagrammatic signs they are replacing (as the human factors 'experts' claim), it's interesting to note that only a total of four such signs existed in the entire country (as compared with hundreds of diagrammatics) before the 2009 MUTCD was issued.

[AsphaltPlanet]

Another new sign for the 75/85 split already? That one was just replaced a couple years ago, new enough to be Series E(M) and everything. And that's without even going into the ludicrousness of having a single BGS spanning 6+ lanes.

I wonder if there is a higher than normal accident rate approaching the interchange despite the new signage.  Sometimes that is motivation for an engineer to try and improve signage further.

[on_wisconsin]

Unless I'm missing something, there's a problem here.  Georgia's proposed "arrow per lane" BGSes don't depict any 'optional' exit lanes - which is the only configuration these signs are supposed to be used for.

Wait, I thought they are still allowed as an option when used as illustrated above.

[J N Winkler]

Unless I'm missing something, there's a problem here.  Georgia's proposed "arrow per lane" BGSes don't depict any 'optional' exit lanes - which is the only configuration these signs are supposed to be used for.

Wait, I thought they are still allowed as an option when used as illustrated above.

No, they aren't--in fact it is a MUTCD Standard statement that they shall not be used when there are no option lanes.  The MUTCD retains the old stippled-arrow diagrammatics for use on existing freeways but imposes an identical restriction (option lanes only).  This is a change from previous editions of the MUTCD, which allowed stippled-arrow diagrammatics at exits without option lanes.

My theory--assuming that GDOT's traffic people are not oblivious to the option-lane requirement, which I suppose is always at least a distant possibility--is that these installations are a test to determine whether it is really necessary to ban arrow-per-lane diagrammatics at splits without option lanes.  GDOT uses many stippled-arrow diagrammatics and under current MUTCD language these would have to be replaced with arrow-per-lane diagrammatics if those locations were ever reconstructed, but in fact neither kind of diagrammatic is currently used at either of the locations shown above.

[kphoger]

My theory--assuming that GDOT's traffic people are not oblivious to the option-lane requirement, which I suppose is always at least a distant possibility--is that these installations are a test to determine whether it is really necessary to ban arrow-per-lane diagrammatics at splits without option lanes.  GDOT uses many stippled-arrow diagrammatics and under current MUTCD language these would have to be replaced with arrow-per-lane diagrammatics if those locations were ever reconstructed, but in fact neither kind of diagrammatic is currently used at either of the locations shown above.

Only a distant possibility?  I just assumed someone saw a big interchange with multi-lane exits and shouted, Arrow per lane!  Seriously, though, if we put our bias aside, is there really any reason not to allow APL in the absence of option lanes?  The only thing I don't like are the curvy arrows:  I'd prefer straight, angled ones.

[roadman]

I'm still waiting for substantive proof based on actual real-world installations (as opposed to polling people using driving simulators) that the benefits of APL over 'stipple-head arrrow' diagrammatics are great enough to justify the increased size and expense of the much larger panels and structures required for these signs.

[kphoger]

I'm still waiting for substantive proof based on actual real-world installations (as opposed to polling people using driving simulators) that the benefits of APL over 'stipple-head arrrow' diagrammatics are great enough to justify the increased size and expense of the much larger panels and structures required for these signs.

Right, but that's a separate debate.  The question is whether there's a real reason to allow them on option lane interchanges but not allow them on non—option lane interchanges.

[PurdueBill]

I don't get why the arrow-per-lane would be used in the first place in a non-option situation, even if allowed.  Ordinary pull-through and exit lane signs should do the job.  I thought that the arrow-per-lane was intended to deal with situations where ordinary signs would require dancing arrows and more than one arrow pointing to the same lane from separate signs, and because the stippled arrows were thought to be too subtle sometimes.  If there are no option lanes, then there doesn't seem to be a need for an arrow-per-lane sign at all, allowed or not.

[Alps]

Anyone wanna point out that you don't use "EXIT ONLY" on these particular signs? Besides the obvious "these are the wrong application" and "these are the devil's handicraft."

[Duke87]

Technicalities of the MUTCD aside, I see nothing functionally wrong with these signs. They convey the needed message clearly and concisely, if perhaps at an expense of extra panel space.

The only problem I have with "big signs" like these is that they lose their impact if overused. Really, a diagrammatic of any sort should only precede a major interchange. If it's an exit to some urban or suburban arterial that happens to have an option lane, the old method of one plain arrow, one arrow in exit only stripe (now banned, unfortunately) would be preferable because it is lower key. An exit like that should not be emphasized over the others around it just because of a lane striping quirk.

[roadfro]

Anyone wanna point out that you don't use "EXIT ONLY" on these particular signs? Besides the obvious "these are the wrong application" and "these are the devil's handicraft."

If an option lane with additional drop lane(s) were present, as with intended use in the MUTCD, you would use EXIT ONLY plaques for the drop lane arrows. Unless I'm missing something...?

Technicalities of the MUTCD aside, I see nothing functionally wrong with these signs. They convey the needed message clearly and concisely, if perhaps at an expense of extra panel space.

The only problem I have with "big signs" like these is that they lose their impact if overused. Really, a diagrammatic of any sort should only precede a major interchange. If it's an exit to some urban or suburban arterial that happens to have an option lane, the old method of one plain arrow, one arrow in exit only stripe (now banned, unfortunately) would be preferable because it is lower key. An exit like that should not be emphasized over the others around it just because of a lane striping quirk.

The MUTCD states that APL signs shall be used for all major interchanges/splits with multi-lane exits (with an option lane), and encourages their consideration for similar intermediate interchanges. They are not encouraged for use at service/minor interchanges--the signing method now encourages conventional signing (single arrow in advance but dual arrow at the exit) with lane-use regulatory signing.

I'll note that Nevada DOT has done a major sign replacement on I-80 in Reno since adopting the 2009 MUTCD--they implemented APLs for a major interchange, but still used the old method (of one standard arrow and one exit only arrow) for service interchanges with option lanes.

[vdeane]

I like arrow-per-lane replacing diagrammic signs, but I hate it when they replace the old one plain arrow/one exit-only signs.

[Alps]

Anyone wanna point out that you don't use "EXIT ONLY" on these particular signs? Besides the obvious "these are the wrong application" and "these are the devil's handicraft."

If an option lane with additional drop lane(s) were present, as with intended use in the MUTCD, you would use EXIT ONLY plaques for the drop lane arrows. Unless I'm missing something...?

Hm, they don't seem to cover the case of 3+ lane exits. It seems aesthetically terrible to have the panels beneath every single arrow like that, not to mention confusing. I would really want to see at most one set of panels.

[agentsteel53]

Hm, they don't seem to cover the case of 3+ lane exits. It seems aesthetically terrible to have the panels beneath every single arrow like that, not to mention confusing. I would really want to see at most one set of panels.

I made a very quick mockup of what I think might be a more aesthetically pleasing solution.



don't mind the tilted rectangle and pixelated font.  it's a very quick mockup, not a joke at Mexico's expense.

(I googled "arrow per lane sign" and what I started with was one of the first images.  I believe the photo belongs to a poster here, but can't remember who.)

[Duke87]

That's fine for two arrows. As for the 75/85 example, you've got two multiplexed routes splitting. Really, neither direction is an "exit", so I would just forget about the whole "exit only" thing entirely and put all plain arrows.

[agentsteel53]

That's fine for two arrows.

my idea would work for exit-only lanes as well.

[realjd]

I'm still waiting for substantive proof based on actual real-world installations (as opposed to polling people using driving simulators) that the benefits of APL over 'stipple-head arrrow' diagrammatics are great enough to justify the increased size and expense of the much larger panels and structures required for these signs.

Think global. Arrow-per-lane signs have been in use used extensively in other countries for decades so its not exactly a new idea or some sort of grand experiment on our part.

[Scott5114]

I'm still waiting for substantive proof based on actual real-world installations (as opposed to polling people using driving simulators) that the benefits of APL over 'stipple-head arrrow' diagrammatics are great enough to justify the increased size and expense of the much larger panels and structures required for these signs.

Think global. Arrow-per-lane signs have been in use used extensively in other countries for decades so its not exactly a new idea or some sort of grand experiment on our part.

Perhaps they are not new, but if the existing sign types do a comparable job for less money, what exactly is the benefit of changing to APL? To make German tourists feel at home?

[realjd]

I'm still waiting for substantive proof based on actual real-world installations (as opposed to polling people using driving simulators) that the benefits of APL over 'stipple-head arrrow' diagrammatics are great enough to justify the increased size and expense of the much larger panels and structures required for these signs.

Think global. Arrow-per-lane signs have been in use used extensively in other countries for decades so its not exactly a new idea or some sort of grand experiment on our part.

Perhaps they are not new, but if the existing sign types do a comparable job for less money, what exactly is the benefit of changing to APL? To make German tourists feel at home?

I was making no claim as to their effectiveness or necessity. I merely was arguing that the fact that there aren't many in the US doesn't necessarily mean there is no research, testing, or experience with them.

[SignBridge]

I don't think OAPL signs as specified in the 2009 Manual will catch on in the US. I think state DOT's will be reluctant to use them because they are gross overkill. There is too much wasted space on the lower portion of the sign. This will require unreasonably huge signs, especially over very wide roadways.

I wouldn't be surprised if in the next MUTCD revision some years down the line, the FHWA modifies the design to a more reasonable format, something like that used on the German Autobahn system. They use similar arrows placed between and beside the legends, making much more efficient use of sign-space.

Having said that, I will also re-state my opinion from earlier discussions that the FHWA created a problem where there wasn't one re: 2 arrows for different directions over an optional lane.  The solutions they have come up with including OAPL signing (at major xchanges) and single arrow advance signs with double arrow at the gore point (for intermediate xchanges) are so "flat-footed" that the cure is worse than the disease in my opinion.