Mile Marker 0 on Interstates: Documentation for Rationale?

[kinupanda]

I would surmise that, while they may not necessarily think about it on a regular basis, the average motorist in the U.S. knows that mile marker 0 on an Interstate is at the westernmost/southernmost point of the route within a state, and that the mile markers (and consequently exit numbers) increase before resetting at the state line.* However, is there any documentation as to why the westernmost/southernmost point was chosen instead of the easternmost/northernmost point, or some other combination? One may speculate that this scheme was deliberately chosen to match that of the grid: since 2di route numbers increase from west to east and from south to north, the powers that be may have decided to apply that logic to the mileposts on said routes as well. However, I'm looking for something sourced instead of speculative, and my searches (both on this forum and elsewhere) haven't turned up anything useful. Is there, for example, a document from the FHWA, meeting minutes, or something otherwise official that definitively indicates the rationale for the choice?

*: Again, they likely could point this out as a rule of thumb for 2dis. Let's not worry about clear exceptions such as circumferential routes, special situations such as I-24 reentering Tennessee after dipping into Georgia, other exceptions of interest to those of us on this forum, etc., since those are immaterial to the actual question in this topic.

[hotdogPi]

On a coordinate plane, numbers increase going up (y) and to the right (x).

[CtrlAltDel]

I would surmise that, while they may not necessarily think about it on a regular basis, the average motorist in the U.S. knows that mile marker 0 on an Interstate is at the westernmost/southernmost point of the route within a state, and that the mile markers (and consequently exit numbers) increase before resetting at the state line.*

I would disagree. I think the average motorist knows that mile markers start from the state line, but not that there's any systematic choice of which state line.

But as to your actual question, I don't know. The western border makes sense for me, though, while the southern border doesn't, since we read from left to right and from the top down, and the top is associated with north and not south.

[NWI_Irish96]

The numbers of the interstates themselves increase from west to east and from south to north, so it makes sense to have the mileage increase in the same directions.

[Rothman]

The numbers of the interstates themselves increase from west to east and from south to north, so it makes sense to have the mileage increase in the same directions.

NY laughs at you.

[ErmineNotyours]

But as to your actual question, I don't know. The western border makes sense for me, though, while the southern border doesn't, since we read from left to right and from the top down, and the top is associated with north and not south.

Plants grow from down to up, so mileage growing from down to up (on a North-up oriented map) makes sense.

[ilpt4u]

I always figured "Zero"  was Westpoint and Southpoint, because the US is so NE-centric, population-wise, and was even moreso when the Interstate System was born

Figured it was numbered that way so travelers from the NE Corridor traveling South and/or West have their mileage to the state lines they will encounter on their journey

I have never researched any actual reason West and South were set as "Zero"  points

[SP Cook]

Would it not be a function of numbering interstates in the reverse of the US system?  Lowest US highways are east or north, lowest Interstates are west and south.  Thus mile markers would be the same.

[Brandon]

The numbers of the interstates themselves increase from west to east and from south to north, so it makes sense to have the mileage increase in the same directions.

NY laughs at you.

Illinois got with the program, New York can too.

[kphoger]

I would surmise that, while they may not necessarily think about it on a regular basis, the average motorist in the U.S. knows that mile marker 0 on an Interstate is at the westernmost/southernmost point of the route within a state, and that the mile markers (and consequently exit numbers) increase before resetting at the state line.*

I would disagree. I think the average motorist knows that mile markers start from the state line, but not that there's any systematic choice of which state line.

But as to your actual question, I don't know. The western border makes sense for me, though, while the southern border doesn't, since we read from left to right and from the top down, and the top is associated with north and not south.

I think even that goes too far.  The only drivers who know mileage resets at state lines are those that have driven across multiple states on Interstate highways–and only the subset of those who actually paid attention and noticed.

For what it's worth, mileage in Mexico counts down/up to the next control city, not the state line that might be in between, and there's no consistent directionality that I've noticed.  This does mean that the numbers can reset multiple times within a state.  (Putting the zero point in the control city is, in my opinion, more intuitive than putting it at a state line.)

[Rothman]

The numbers of the interstates themselves increase from west to east and from south to north, so it makes sense to have the mileage increase in the same directions.

NY laughs at you.

Illinois got with the program, New York can too.

NY laughs at you, too.

[Brandon]

The numbers of the interstates themselves increase from west to east and from south to north, so it makes sense to have the mileage increase in the same directions.

NY laughs at you.

Illinois got with the program, New York can too.

NY laughs at you, too.

Can NY laugh at the feds though?

[Rothman]

The numbers of the interstates themselves increase from west to east and from south to north, so it makes sense to have the mileage increase in the same directions.

NY laughs at you.

Illinois got with the program, New York can too.

NY laughs at you, too.

Can NY laugh at the feds though?

NY has done so and been slapped on the wrist.

(personal opinion emphasized)

[kphoger]

In México, kilometer-posts count down to the next major city rather than a state line.  It makes sense, but it's also kind of humorous to see a distance sign that says [CITY NAME   68] right next to a km-68 post.

For what it's worth, mileage in Mexico counts down/up to the next control city, not the state line that might be in between, and there's no consistent directionality that I've noticed.  This does mean that the numbers can reset multiple times within a state.  (Putting the zero point in the control city is, in my opinion, more intuitive than putting it at a state line.)

To highlight the above bolded statement, I present the three examples below.

Carr. Fed. 57 – Coahuila – km 15 (zero point near Allende)

Carr. Fed. 57 – Coahuila – km 15 (zero point in Monclova)

Carr. Fed. 57 – Coahuila – km 15 (zero point at the junction with Fed. 40)

[Scott5114]

On a coordinate plane, numbers increase going up (y) and to the right (x).

Oh, dammit, I never made this connection, despite my self-education about the road system occurring about the same time I had to worry about coordinate planes in high school.

[kinupanda]

On a coordinate plane, numbers increase going up (y) and to the right (x).

Oh, dammit, I never made this connection, despite my self-education about the road system occurring about the same time I had to worry about coordinate planes in high school.

This is very logical, and I know I'd be pleased if that ended up being the true rationale. Even if not, it provides a meaningful association to help the average motorist (well, at least the ones who stayed awake in math class) remember how mile markers increase.