From: Ron Newman (firstname.lastname@example.org)
Just for the hell of it, I decided to make a list of all known places
where the US Interstate Highway System's numbering system for
2-digit routes is violated.
The 2-digit numbering system is based on the principle that:
- north-south highways are numbered in increasing order as you go
from west (I-5 in California) to east (
- east-west highways are numbered in increasing order as you go
from south (I-4 in Florida) to north (
This standard is violated for a number of perfectly good reasons:
- Some interstate highways are diagonal rather than strictly
east-west or north-south, especially those that follow
the southeastern US coastline or the Appalachian Mountains
- Some highways were extended beyond their originally planned terminus
- Some highways were renumbered in the 1970s, when the authorities
decided to get rid of numbers like "15W" and "80S"
- Some highways were relocated from their original planned alignment
When you think about it, it's actually surprising how _few_ times
the standard is violated.
Anyway, here's the list, as taken from my 1993 AAA Road Atlas.
Additions and corrections are welcome.
- I-20: See I-26
- I-24: Crosses
I-40 at Nashville, Tennessee. The
section from Nashville
southeast to Chattanooga is south of I-40.
Reason: I-24 is a diagonal Interstate.
- I-26: Crosses I-20 at
Columbia, South Carolina. The section from Columbia
southeast to Charleston is south of I-20.
Reason: I-26 is a diagonal Interstate.
- I-40: See
Crosses I-40 at Oklahoma City. The Bailey
from Oklahoma City southwest to Wichita Falls, Texas,
is south of I-40.
Reason: I-44 is diagonal, and the Bailey
Turnpike was added to I-44
after the original numbering plan was designed.
I-70: See I-74
- I-74: Crosses
I-70 just west of Indianapolis.
The section from
Indianapolis southeast to Cincinnati is south of
I-74 is a (somewhat) diagonal Interstate.
(Note: If I-74 is extended into the
Carolinas as proposed, the
"violating" section will be much longer.)
- I-82: All of this highway, from Ellensburg,
Nowhere, Oregon (where it meets I-84), is
north of I-84.
Reason: I-84 used to be I-80N; when it was
changed, I-82 wasn't.
- I-84: see I-82
- I-90: Splits from
I-94 in Chicago, then crosses
it in Gary, Indiana.
The section from the Dan Ryan Expressway to Gary is
I-94. There is no violation west or east of this
Reason: No good reason that I can see. In fact,
I-90 and I-94
were originally numbered the opposite way here, and there
was no violation then!
See I-90, I-96
- I-96: Crosses
I-94 in Detroit, and continues for
southeast to I-75.
Go to the list of 2 digit Interstates
- I-59: Crosses
I-65 at Birmingham, Alabama. The
section from Birmingham
northeast to Chattanooga is east of I-65.
Reason: I-59 is a diagonal Interstate.
- I-65: See I-59
- I-69: Crosses
I-75 at Flint, Michigan, and
continues due east
to the Canadian border at Port Huron.
Reason: this section was added after the original numbering plan.
- I-71: Joins
I-75 a few miles south of Cincinnati,
and splits from
it in Cincinnati. The section from Cincinnati to Cleveland --
which is nearly all of I-71 -- is east of
Reason: I-71 is diagonal. But the
numbering is still a bit
puzzling, given the relative length and importance of
the non-violating and violating sections.
- I-75: See I-69, I-71, I-85
- I-77: see I-81
: Joins, then splits from, I-77 near
For a few miles you are actually going simultaneously
north on I-77 and south on
section of I-81
southwest of this point is west of I-77.
Reason: I-81 is a diagonal Interstate that
the Appalachian Mountain range. Much of it, including
this section, is largely east-west.
- I-85: Crosses
I-75 in Atlanta. Crosses
Charlotte, North Carolina.
The section from Montgomery to Atlanta is west of both
I-75 and I-77,
and the section from Atlanta to Charlotte is west of
Reason: I-85 is a diagonal Interstate, and
much of it
is largely east-west.
- I-87: Crosses I-95 in the
Bronx, New York City, and continues south
for another 3 or so miles. (Where does I-87
- I-89: Crosses I-91 at
White River Junction, Vermont. The section
from White River Junction southeast to Concord, New Hampshire,
is east of I-91.
Reason: I-89 is a diagonal Interstate.
- I-91: See I-89
- I-93: Crosses I-95 at
Reading, Mass, north of Boston. I-95 detours
counterclockwise around Boston on Mass. Route 128, while I-93
runs straight through the heart of the city, then
turns clockwise on Route 128 until it meets I-95
again in Canton.
Reason: I-95 was originally intended to go
not around it. In this plan, I-93 and
joined in Charlestown, just across the Charles River
from downtown Boston, and I-93 would not have
south of this point.
: See I-87, I-93