Should I-19 BGS be All metric or standard?

[NE2]

Exit numbers on SH 130 in Texas increase in the wrong direction (violates MUTCD rules for progression of distance posts and exit numbers).

If you want to be that anal, we can call it a beltway, in which case the exit numbers increase in the correct direction.

[corco]

But where are all the people that are confused by metric signing?  If you yourself have driven on I-19, can you truthfully say you have been confused by the metric signing?

I wouldn't say I was confused, but I do definitely notice it. I've also got a decent education and a decent amount of experience driving/riding in Canada- I would hazard that to the truly uneducated (high school dropouts and the like), the metric system probably isn't something that is terribly familiar (unless they came from Mexico, which I'll admit a good chunk of the uneducated in southern Arizona do) and could lead to confusion on that level.

Lack of conformity goes well beyond instances of signs being "slightly disproportional."  I have seen Interstate guide signs intended for 75 MPH rural contexts with 10 2/3" UC/8" LC primary destination legend (violates MUTCD sizing rules).  Exit numbers on SH 130 in Texas increase in the wrong direction (violates MUTCD rules for progression of distance posts and exit numbers).  We still have holdouts with sequentially numbered exits (violates new MUTCD ban on sequential numbers).  Many states do not use exit numbers on non-Interstate freeways (violates new MUTCD requirement for exit numbers on all freeways).  Need I go on?

No, but is the general public more likely to notice any of those things or signage that is in kilometers instead of miles? I'd hazard that the latter is a lot more  A) obvious and B) likely to affect their navigation. For instance, a driver unfamiliar with the distance of 1 km could choose to pass a truck before exiting, and then not get into the exit lane in safe time, cutting off the truck and braking. A mis-sized speed limit sign still conveys the same message, and exit number anomalies are likely to be unnoticed by the majority of drivers, and certainly with advance signage any differences would be offset on site.

I like the metric signs on I-19 and I would like to see them replaced in kind.  But why resort to special pleading when there are perfectly rational arguments that can be made in favor of the current arrangement?  As the only Interstate with metric guide signing in a country where English units rule, I-19 is an anomaly, but we do not have traffic engineering standards merely to eliminate anomalies; instead, we have them to ensure that any which are allowed to exist do not interfere with safety.

The only argument I'd feel comfortable advancing is that they should be grandfathered because they already exist.

[J N Winkler]

I wouldn't say I was confused, but I do definitely notice it. I've also got a decent education and a decent amount of experience driving/riding in Canada- I would hazard that to the truly uneducated (high school dropouts and the like), the metric system probably isn't something that is terribly familiar (unless they came from Mexico, which I'll admit a good chunk of the uneducated in southern Arizona do) and could lead to confusion on that level.

Maybe--but I am still skeptical.  Aside from the different units system, the progression of advance guide and exit direction signs is pretty plain-vanilla on I-19, and that in itself is a pretty powerful navigational cue.

I-19 is actually the first highway signed in metric I ever drove since I got to it (in 1998) before I started driving in Canada (2001) or Mexico (2002).  I had no difficulty with the metric signing.

No, but is the general public more likely to notice any of those things or signage that is in kilometers instead of miles?

Trust me, you will notice it if you are a stranger driver.  "Why can't I read that sign?"  "Why are the exit numbers in the 400's and not going up in the right direction?"  "Passed Exit 1 a while back.  Why is it taking forever to reach Exit 2?"  "What number is the exit I want?  Why don't any of these exits have numbers?"  And so on.  The lack of MUTCD mileposts on California freeways caused me problems the first time I drove in California, believe it or not--far more than I experienced with metric signs on I-19.

I'd hazard that the latter [metric] is a lot more  A) obvious and B) likely to affect their navigation. For instance, a driver unfamiliar with the distance of 1 km could choose to pass a truck before exiting, and then not get into the exit lane in safe time, cutting off the truck and braking.

I think that scenario is unlikely.  I-19 is km-posted, and exit spacing is wide enough that a driver unfamiliar with kilometers (and who could be expected to be more alert to cues provided by distance posts because of that lack of familiarity) would have enough opportunity to learn how long a km is before he had to decide whether to overtake a truck.  Also, passing within 1 km of an exit means initiating the maneuver when an advance guide sign is in sight, which is always dicey--no matter what the unit system is--when you don't know the road but do know you want to take the upcoming exit.

Plenty of reckless people would attempt overtakes at 1 km distance from the exit they intend to take, but I don't think the units system would be a factor of any importance in that decision.  (Overtaking at 1 km is more or less the same as overtaking at 1/2 mile.)

I like the metric signs on I-19 and I would like to see them replaced in kind.  But why resort to special pleading when there are perfectly rational arguments that can be made in favor of the current arrangement?  As the only Interstate with metric guide signing in a country where English units rule, I-19 is an anomaly, but we do not have traffic engineering standards merely to eliminate anomalies; instead, we have them to ensure that any which are allowed to exist do not interfere with safety.

The only argument I'd feel comfortable advancing is that they should be grandfathered because they already exist.

I would not feel comfortable pushing that argument at all.  First, it runs out of road when the sheeting on the current I-19 signs wears out, a circumstance which will be at hand in probably another 10 years.  (The pending partial replacement in my view is somewhat premature, though I don't have access to any retroreflectivity measurements Arizona DOT may have done to justify it.)  Second, when equitable interests are not being protected (e.g., an investment in obsolete components of excess durability--California and porcelain enamel come to mind), it is a pretty poor defense for something that is a bad idea in the first place.

[myosh_tino]

Lack of conformity goes well beyond instances of signs being "slightly disproportional."  I have seen Interstate guide signs intended for 75 MPH rural contexts with 10 2/3" UC/8" LC primary destination legend (violates MUTCD sizing rules).  Exit numbers on SH 130 in Texas increase in the wrong direction (violates MUTCD rules for progression of distance posts and exit numbers).  We still have holdouts with sequentially numbered exits (violates new MUTCD ban on sequential numbers).  Many states do not use exit numbers on non-Interstate freeways (violates new MUTCD requirement for exit numbers on all freeways).  Need I go on?

Heck, look at the state of California... no numbered exits until the early 2000's, exit tabs incorporated into the guide sign (i.e. no external tabs), cutout US route shields, cutout and non black and white route shields, undersized exit "tabs", no reference markers (mileposts) and on and on.  Given the fact that a vast number of signs now violate the 2009 MUTCD, look for the lack of conformity to skyrocket in the Golden State (arrow-per-lane signs? Pfft, yeah right!)

As far as I-19 is concerned, I say leave it metric.  As much as I don't care for the metric system, I-19 has existed this long with metric units without a major outcry from the general public so I don't see what all the hub-bub is all about.

[vdeane]

Yeah, I imagine CA won't ever have arrow-per-lane signs... there's no way they'd stand up to the high wind loads unique to CA that prevent them from having tabs!

[english si]

I just think all highways should be in English.

So the correct spelling of 'through'? that would cost a lot to change. Not to mention using yards, and feet only being on height and weight restriction signs, and metric tons for weight limits (plus Celsius for temperature if that comes up)...

I think you meant American, rather than English

As you can see from the above, I can be pretty anal retentive, but I-19 (or if some road in the UK was signed in metric) doesn't bother me. It's a little quirk that makes life interesting, much like how we still use miles, etc on the road in the UK despite almost everything else being officially metric and all the nations around us being metric.

[corco]

Trust me, you will notice it if you are a stranger driver.  "Why can't I read that sign?"  "Why are the exit numbers in the 400's and not going up in the right direction?"  "Passed Exit 1 a while back.  Why is it taking forever to reach Exit 2?"  "What number is the exit I want?  Why don't any of these exits have numbers?"  And so on.  The lack of MUTCD mileposts on California freeways caused me problems the first time I drove in California, believe it or not--far more than I experienced with metric signs on I-19.

You might be able to convince me that people who are used to mileage based exits would notice sequential exits, but I'd bet the majority of travelers neither realize nor care that exits increase from south to north and west to east- certainly not enough to notice a difference.  A lack of exit tabs could be weird when you're used to navigating by exit number, but it's not something that could pose a safety threat.

A driver misjudging the distance of a kilometer could- it's unlikely, but it could actually pose a safety threat. A driver that doesn't know how far a kilometer is or mistakes it for a mile could very well make distance-based decisions that are dangerous. Just because you or I wouldn't doesn't mean that it couldn't happen.

You have to remember that roadgeeks are not standard travelers. The experience you or I or pretty much anybody reading this forum have driving down the road  is not a very good representation of what the actual traveler notices or cares about. Our experiences are nearly irrelevant, because we're trained to be hyper-astute to anomaly. Even if you're optimistic- say 75% of travelers notice and are aware of things like exit numbers and their function (I'd say that 75% is optimistic for being aware of how exit numbers are supposed to work), that leaves a full 25% of travelers who don't. That's a very significant number.

But I'd bet nearly 100% of travelers notice when things are posted in metric, and some of those have little idea how metric units play out over space.  I'd say that once again, the roadgeek brain seems to be a lot more spatially aware than the average bear- so your ability to adapt to a kilometer instead of a mile is probably a lot better than the general populus.

I would not feel comfortable pushing that argument at all.  First, it runs out of road when the sheeting on the current I-19 signs wears out, a circumstance which will be at hand in probably another 10 years.  (The pending partial replacement in my view is somewhat premature, though I don't have access to any retroreflectivity measurements Arizona DOT may have done to justify it.)  Second, when equitable interests are not being protected (e.g., an investment in obsolete components of excess durability--California and porcelain enamel come to mind), it is a pretty poor defense for something that is a bad idea in the first place.

Oh- I'm not advocating never replacing the signs, but I think an argument can be (and has been) made that you could replace the current signs with metric units simply because the old ones are and the difficulty in adjusting wouldn't be worth the gains from changing (You could argue the same thing with sequential exits).

One thing that does need to happen regardless is consistency in units- the border checkpoint signs, for instance, are in standard units, as are call box signs.

As far as reflectivity- the southbound are mostly OK, but some of the northbound signs are in pretty bad condition.

[1995hoo]

....

My desire for metric is selfish- I just like the uniqueness.

My preference that all signs be metric is based on the fact that I understand that system a lot better than the gibberish that predominates in the USA. All the bizarre conversions involving inconsistent amounts like 12s, 16s, 8s, 5280s, etc., simply don't make any sense to me.

[J N Winkler]

You might be able to convince me that people who are used to mileage based exits would notice sequential exits, but I'd bet the majority of travelers neither realize nor care that exits increase from south to north and west to east- certainly not enough to notice a difference.

I don't think that is necessarily true.  Information about progression of exit numbers appears in materials geared to lay audiences and it is something that becomes very obvious to people studying maps to plan long-distance roadtrips.  It is the kind of information you can expect to see in AAA TripTiks, for instance, which are not designed for roadgeeks by any stretch of the imagination.

I was not a road enthusiast in any meaningful sense when I started driving long-distance, but the correspondence between exit numbers and mileposts and the progression of milepointing from south to north and west to east was something I noticed early on.

A lack of exit tabs could be weird when you're used to navigating by exit number, but it's not something that could pose a safety threat.

By itself, probably not--but for drivers who expect that guidance to be provided and find it absent, it contributes to disorientation, which in turn can be a contributing factor in a crash.  For example, the lack of exit numbers and a relatable distance-posting system on I-10 in California made it difficult for me to plan rest stops, tell how far I was from Los Angeles, etc.

A driver misjudging the distance of a kilometer could- it's unlikely, but it could actually pose a safety threat. A driver that doesn't know how far a kilometer is or mistakes it for a mile could very well make distance-based decisions that are dangerous. Just because you or I wouldn't doesn't mean that it couldn't happen.

A lot of Swiss-cheese holes would have to line up in order for it to happen, though.

The suggestion that a driver unfamiliar with kilometers could misinterpret distance and initiate a maneuver without a full appreciation of the danger involved assumes that most drivers can take information given in miles and relate it to maneuvers they wish to carry out.  I don't think that is actually true.  I think most drivers rely on a visual assessment of relative speeds, which is invariably imprecise, and make their decision based partly on that and partly on their assessment of where they are in the advance guide signing sequence for an exit.

You have to remember that roadgeeks are not standard travelers.

I have not forgotten that.  I traveled on I-19 before I was a roadgeek, so I have an ordinary driver's perspective on metric signing on I-19.

The experience you or I or pretty much anybody reading this forum have driving down the road  is not a very good representation of what the actual traveler notices or cares about. Our experiences are nearly irrelevant, because we're trained to be hyper-astute to anomaly. Even if you're optimistic- say 75% of travelers notice and are aware of things like exit numbers and their function (I'd say that 75% is optimistic for being aware of how exit numbers are supposed to work), that leaves a full 25% of travelers who don't. That's a very significant number.

There is not much in this argument since drivers vary in their level of familiarity with the roads they are using.  A local driver, for example, doesn't really need to have information about exit numbers because he or she is relying on underlying knowledge of the road system.  A stranger driver, on the other hand, will be aware of exit numbering (especially if trying to follow directions which presume some familiarity with them), partly because he or she will have had to invest in some study of maps in order to come to grips with an alien road network.  The pie piece to worry about, which I think is actually very small, is the stranger drivers who don't understand the basic affordances of the freeway guide signing system.

Think about the people in Wichita who say "I-35" when they mean Canal Route (I-135), or in Tucson who say "I-10" when they mean I-19.  Do you think these people get lost every day on the way to work?  No.  They know their way around, so they have the freedom to be sloppy.  Outsiders can lecture them about their road systems because they have actually had to put some effort into studying them.

But I'd bet nearly 100% of travelers notice when things are posted in metric, and some of those have little idea how metric units play out over space.  I'd say that once again, the roadgeek brain seems to be a lot more spatially aware than the average bear- so your ability to adapt to a kilometer instead of a mile is probably a lot better than the general populace.

Not really.  I know that 1 mile = 1.6093 km, but this doesn't really help me when I am driving, because I don't have any way of accepting, let alone reacting to, precise speed and position inputs.  When I approach an exit, I make a decision as to whether to stay on or turn off, and if the latter, whether to overtake or not, based on whether I can see advance guide signs for that exit.  Placement of advance guide signs is pretty standard on I-19 notwithstanding the use of metric units.  If a sign tells me "Arivaca Rd 500 m," I interpret that as "get ready to exit for Arivaca Road here," the same way I would if I saw a sign saying "Arivaca Rd 1/4 mile."

For drivers of whatever level of familiarity with traffic signing standards, consistent progression of advance guide and exit direction signs is more important than the units actually expressed on the advance guide signs.

Let me try to illustrate with an example taken from a different context.  Per UVC, it is legally required to signal 100 feet in advance of a turn or lane change on a conventional road, and 300 feet in advance on a high-speed road.  Do you think the police pull people over for not turning on their blinkers until 99 feet before the turn on conventional roads, or 299 feet on high-speed roads?  No.  In practice the usual criterion for turn-signal enforcement is whether the signal is visible at all.

P.S.  I actually find metric signing a bit harder to deal with in Canada and Mexico than on I-19, because I-19 still has a speed limit in customary units.  I like to comply with speed limits when I am on long-distance roadtrips (I don't want to be constantly looking out for American bears, let alone foreign ones), and setting the cruise control for speed limits in km/h means looking for figures on a hard-to-read second dial.

[Quillz]

Switch all BGS back to customary units. I prefer metric, but the USA uses customary units.

[SP Cook]

Borders mean things.  Things change at borders.  In the USA "standard" units are used, signs are in English, and certain driving rules apply.  When you get to a border, you are in another jurisdiction, and other rules apply.  You know this, because crossing a border involves an activity that is certainly more complex than merging from one interstate to another. 

This is safe.  Everyone, even the most casual driver, know exactly when the measurement system, language, and other rules of the road will change.  At the border.  Not when you get off I-10 (or worse yet, a side road) and onto I-19.  Safe, consistant, and simple.  And, as to "Mexicans not knowing what is going on", this is silly.  First, of course, it is naive and silly to think that I-19 is the only road driven by Mexicans, or any other people that use metric system.  Millions of people drive in the USA and adjust to "standard" signage every day.  But more importantly, millions of people (including myself) have certainly driven safely in both Canada and Mexico w/o any language or measurement issues.  Doping out the little bit of any of the three major North American languages used in road signage is not even hard, the words are near cognates and easily figured out from the context, sign shape, and such. 

[vdeane]

The myth that I-19 is metric because of Mexico was already debunked.

[kkt]

Keep I-19 metric.  I hope metric spreads to other highways.  The world has made its choice, based on merit.  The U.S. will have to convert eventually.  The longer we wait, the more painful it will be.

A special dumbbell award to California, for not adopting exit numbers based on km back around 2000 when they started signing the exit numbers.

[Bickendan]

Would have been interesting to see Exit 1274 at Hilt on I-5...

[Henry]

Or perhaps Exit 1416 on I-10 in Texas!

I say leave I-19 as is, because of its uniqueness. Also, when you first pass Exit 99 and think that you are 99 miles from Mexico, and then make it to the border thinking: "Wow, that was the quickest 99 miles I've ever driven", not realizing it was closer than you originally thought, it can make for a hilarious road trip story.

[texaskdog]

Only way metric will ever work in the US is to make everything metric & just force us to get used to it.  Just like the dollar coins, if you don't get rid of the paper dollars they will fail.

[Brandon]

Keep I-19 metric.  I hope metric spreads to other highways.  The world has made its choice, based on merit.  The U.S. will have to convert eventually.  The longer we wait, the more painful it will be.

A special dumbbell award to California, for not adopting exit numbers based on km back around 2000 when they started signing the exit numbers.

Why?  A dual system works just fine.  We don't need to switch our roads over to a system people don't want to use.  Hell, the Canucks still use Imperial for a lot of things even with the switch over in the 70s.

[TheStranger]

Why?  A dual system works just fine.  We don't need to switch our roads over to a system people don't want to use.  Hell, the Canucks still use Imperial for a lot of things even with the switch over in the 70s.

And the British - despite going metric for just about everything - still use miles like we do.

When I-19 and Delaware 1 are the ONLY examples - nationwide - of metric exit numbers, that really doesn't present a case that the switchover for distance units is going to happen any time soon in the US.

[myosh_tino]

A special dumbbell award to California, for not adopting exit numbers based on km back around 2000 when they started signing the exit numbers.

Wait... what?!?!?  Why should California do that and use a system that NO ONE (with the exception of I-19 and DE-1) else in the US uses.  There was absolutely NO push in the US to convert to metric in 2000 so why does California get the "dumbbell award" for using a system that the rest of the country uses, namely mileage based exit numbering.  That comment just doesn't make any sense to me.

Besides, IIRC, all metric signs were removed from the current MUTCD and in California's case, all of their standard plans, which were in metric, were converted back into Imperial units a few years ago.

[agentsteel53]

in California's case, all of their standard plans, which were in metric, were converted back into Imperial units a few years ago.

does this mean there are signs out there which are exact multiples of centimeters in key dimensions?  I have never been able to spot such a thing.  sometimes in Canada I can see what is a metric sign that is attached to an inch-based signpost because the bolts are just slightly askew, but I've never seen such a thing in the US.

[myosh_tino]

in California's case, all of their standard plans, which were in metric, were converted back into Imperial units a few years ago.

does this mean there are signs out there which are exact multiples of centimeters in key dimensions?  I have never been able to spot such a thing.  sometimes in Canada I can see what is a metric sign that is attached to an inch-based signpost because the bolts are just slightly askew, but I've never seen such a thing in the US.

I think I may have misspoke.  I believe Caltrans' standard plans were in dual units (Imperial and metric) with the metric version being the "preferred" version.

[J N Winkler]

does this mean there are signs out there which are exact multiples of centimeters in key dimensions?  I have never been able to spot such a thing.  sometimes in Canada I can see what is a metric sign that is attached to an inch-based signpost because the bolts are just slightly askew, but I've never seen such a thing in the US.

I don't think so.  Back when Caltrans was still dimensioning signing plans in metric units, the measurements were typically odd multiples of 5 mm, rather than 1 cm:  so, for example, the word "MILE" in a distance expression (normally 12" tall in Caltrans sign specs approved as part of the Great Redrawing of 1971) was 305 mm rather than 300 mm.  Caltrans was one of the earliest state DOTs to attempt conversion to metric units for construction, and stuck with it after many other state DOTs abandoned their metrication initiatives, but with all the old English-units hardware it has and its emphasis upon reusing and recycling, I don't think Caltrans ever felt free to hard-convert instead of soft-convert.  (In the context of metrication, "soft conversion" implies near-exact conversion of English units into metric units, while "hard conversion" entails the added step of rounding the soft-converted values up or down to "nice" numbers in metric.)

It cannot be overstated that there is a huge divide between converting to metric for distance expressions on signs and converting to metric on construction plans sets.  The former is essentially window-dressing; it is possible to have metric unit expressions on signs made from construction plans dimensioned entirely in English units, and indeed that is how Arizona DOT has always done I-19.  The latter was popular among bridge designers because it allowed bridge strength calculations to be dimensionally correct and thus easy to check (they are not when done in customary units), but almost everyone else hated it.

[kkt]

A special dumbbell award to California, for not adopting exit numbers based on km back around 2000 when they started signing the exit numbers.

Wait... what?!?!?  Why should California do that and use a system that NO ONE (with the exception of I-19 and DE-1) else in the US uses.  There was absolutely NO push in the US to convert to metric in 2000 so why does California get the "dumbbell award" for using a system that the rest of the country uses, namely mileage based exit numbering.

Because the entire rest of the world uses metric, and eventually the US will have to as well.  Continuing to use a system that no one else uses makes our products less competitive in other countries, makes products more expensive for us here, and makes computation unnecessarily hard.  All this was obvious by the 1970s, but not pushed hard enough at the time, so California and other states had the expense of starting to convert a little bit, then converting back to US customary units, and in the future they'll have the expense again of converting back to metric.  Exit numbers based on km would have been a great opportunity to save that future expense without having to change miles to km in other signs at the same time.  Now the expense and confusion of changing exit numbers will be another reason to continue putting off the inevitable.

[english si]

In the UK, we're far more on the cusp of metric, yet I doubt we'll ever change over unless finally forced to go all the way by an outside, authoritarian force.

We have Continental European beer companies making pint (well 568ml) cans/bottles of beer for our market as it's more popular than 500ml cans/330ml bottles - selling them at no more expense (and when it comes to milk, containers in 500ml multiples, rather than 568ml multiples (it's illegal to sell anything but draft beer in pint multiples), tends to be more expensive).

I don't see America going metric unless something drastic has gone wrong. Metric doesn't win in a free market as people don't like it, nor want it, and the US market is big enough to make things in other units without affecting economies of scale - the use of customary measures are not driving prices up or hurting trade, or people would actually want it - other than the standardisation authoritarians.

Then again, while the UK and US going metric would be worrying for freedom and sovereignty, I think there would be far bigger (though probably less visible) infringements of our liberties taking place than our units being banned if it were to happen.

[NE2]

Since most of the US is surveyed in mile squares, changing would have a detrimental effect on distance estimation.