Just to clarify the convention of numbers on city beltways, I'm assuming that the fact many beltways in several states choose to go clockwise with the exits ( and mile posts) starting with a point on the south end are either in the MUTCD or just an unwritten protocol.
All, but the well known Capital Beltway, that uses a counterclockwise system, and briefly has I-95's scheme in Alexandria, uses it. However the points of zero are inconsistent. Some use the southern interstate junction while others may use a river. Then places like I-610 in Texas use an unusual interchange like Texas SH 288 or like the Twin Cities picking a random exchange to reset.
So what is the " official" way that is to be, or isn't there a real way?
The MUTCD calls for clockwise exit numbering. The Capital Beltway is an exception because of the presence of I-95 on the eastern half. When Maryland switched to milepost-based exit numbers in the early 1980s, they numbered I-95 from Exit 2 (I-295 just east of the Wilson Bridge) up to Exit 109 (MD-279, just shy of the Delaware state line). For the other portion of the Beltway between College Park and the American Legion Bridge, they continued the I-95 numbering up to Exit 41.
I-265 in Louisville, being a 3/4 Beltway, is in process of being renumbered and unified mile marker/exit number wise, and the new markers will start at the KY 65/265 interchange, and CCW to the IN 64/265 interchange
Quote from: 1995hoo on November 11, 2024, 08:23:09 AMThe MUTCD calls for clockwise exit numbering. The Capital Beltway is an exception because of the presence of I-95 on the eastern half. When Maryland switched to milepost-based exit numbers in the early 1980s, they numbered I-95 from Exit 2 (I-295 just east of the Wilson Bridge) up to Exit 109 (MD-279, just shy of the Delaware state line). For the other portion of the Beltway between College Park and the American Legion Bridge, they continued the I-95 numbering up to Exit 41.
Way before that, the entire loop was also numbered in the clockwise direction from 1 (US 1 in Alexandria) to 38 (I-295), under the assumption that I-95 inside the Beltway would be completed between Springfield and College Park (of course, we all know what happened to that plan). From the early 1980s up until 2000, VA still used sequential numbers on its portion, which created a series of problems for certain exits, as they were duplicated in both states. Eventually, VA wised up and renumbered its solo portion of I-495 to a continuation of MD's numbers, currently ending at 57 in Springfield. The remainder from there to the Wilson Bridge became a continuation of I-95's mileage and exits (170-177).
As for the first exit/mile zero, I believe that the southernmost point of the loop (6:00) is where the scheme should begin (preferably a major junction), although not all beltways are set up like that, because some begin from the SE (4:00-5:00, i.e. I-695 in Baltimore, west of the Key Bridge collapse site) and others in the SW (7:00-8:00, i.e. I-285 in Atlanta, near the airport).
I-465's exit numbers start just west of the I-65 "south" junction and goes clockwise around the city of Indy.
I've always thought it was weird that IH 610 places exit 1 at SH 288 and not IH-10. I think it should start at IH-10, then proceed clockwise. So US 290 would be exit 3, and Woodway/Memorial would be exit 38
The other beltway that I'm aware of that uses counterclockwise exit numbers, is GA 10 Loop (Athens GA). GDOT has never officially said why it is that way, but I think it's because the segment most used by visitors is from GA 316 (US 29/78) to College Station Rd or US 78 (SR 10) on the east side, and it makes more sense for that stretch to be exit 1 to 7 or 8 compared to exit 1 to 14 or 13.
The STL Beltway consists of 2 states and 2 designations. The mileage/exit numbers reset 3 times. It is not a perfect beltway since I-270 and I/IL 255 cross in the Metro East IL
255 has decreasing/CW exit numbers starting at the aforementioned IL 270/255 interchange and ending at the MO 55/270/255 interchange. (The IL 255 Freeway north of the IL 270/255 interchange has its own exit numbers that increase to the north from the 270/255 interchange, but it is not a part of the beltway)
MO 270 has decreasing/CCW exit numbers beginning at the Mississippi/New Chain of Rocks Bridge/IL state line north of St Louis down to the 55/270/255 interchange.
IL 270 has decreasing/CCW exit numbers beginning at the 55/70/270 interchange (which is outside the beltway proper) and ending at the Mississippi/New Chain of Rocks Bridge/MO state line
IMHO and dabbing into Fictional, IDOT should just continue 270's increasing CCW mileage and exits to eliminate duplication in the Metro area, but whatever
Yeah, its complicated :hmmm:
I-635 in Dallas (LBJ Freeway) is not a full beltway but is about 60% of one. It starts at the bottom and is counterclockwise.