Ep 13: How Interstate Highway Numbering Works (and Why I-60 Doesn't Exist)

Mastering the Commute: Episode 13 – How Highway Numbers Really Work (and Why I-60 Doesn’t Exist)

 Ever seen a meme showing I-50 or I-60 running across the U.S.? Spoiler: they don’t exist—and there's a fascinating reason why. In this 6-minute episode, I take you through the history and logic of America’s highway and interstate numbering systems, from the old U.S. Highways like Route 66 to the massive Eisenhower Interstate system.

We’ll explore:
 🚧 Why I-50 and I-60 were skipped
 🛣️ The difference between U.S. Highways and Interstates
 🔢 How loops, spurs, and 3-digit interstates get their numbers
 🛑 The politics behind strange routes like I-99 and I-238
 🌎 Why California and New York freeways love naming things (hello “the 405”)
 🌾 What’s up with State Highways, County Roads, and Texas Farm-to-Market roads

🎯 Whether you’re a daily commuter or a fellow road geek, this one’s packed with facts you’ve probably never heard—plus a few rabbit holes for the truly curious.

📲 Get more maps, visuals, and extras for this episode at: 

[Episode 13 page on our website]

 📧 Have a highway mystery or a weird sign story? Email me: freewaytrafficexpert@gmail.com

 📺 Don’t forget to subscribe and check out our new daily YouTube Shorts: @MasteringTheCommute
 #InterstateSystem #HighwayMystery #MasteringTheCommute #RoadGeek #TrafficTips #USHighways #FreewayFacts #WhyNoI60

Transcript

Mastering the Commute: your six minute traffic fix

Episode 13: How highway numbers really work (and why I-60 isn't one of them)

[Segment 1 – The Meme and the Mystery]

So I was scrolling a couple of weeks ago, and this meme pops up— showing the U.S. Interstate System. 

And that’s when I saw something weird. It showed I-50 and I-60 running across the nation. 

But guess what … I’ve driven all across the U.S., and I’ve never once seen a sign for I-50 or I-60.  —because they  don’t exist! That tiny bit of “fake news”  led me down a rabbit hole of highway history, numbering logic, and some interesting facts and exceptions that I, the freeway traffic expert , just learned. 

To figure out why those I-50 and 60 don’t exist, we need to dive into a US History lesson..

[Segment 2 – The U.S. Highway System: Origins]

Before the interstates, America had the U.S. Highway System, which was launched in 1926. These are black lettered signs with white background that you can still see today. 

<This was the original national road network—created to bring order to the growing mess of local and regional roads popping up everywhere in the early days of cars.>

The numbering had a basic logic:

• Odd numbers ran vertically, north to south, increasing starting at the east coast going west. .

• Even numbers ran across the country east to west, increasing starting at the north to south.

So, US-1 runs along the East Coast, while US-101 hugs the West Coast.

And in between, you had roads like US-50, us-66 from Chicago to LA, which stretches coast to coast, and US-60, which runs from Arizona to Virginia.

This system worked great—until **everything including traffic started to boom post-WWII.**

[Segment 3 – The Interstate Vision: Eisenhower’s Push]

 During World War II, then General - Eisenhower had seen Germany’s Autobahn system firsthand—how it helped move troops quickly and efficiently. He realized that America needed something similar

So in 1956, Congress passed the Federal-Aid Highway Act, which launched the creation of the Interstate Highway System—officially called the “Dwight D. Eisenhower National System of Interstate and Defense Highways.”

<The original plan called for 41,000 miles of high-speed, limited-access roads.

The budget at the time? $25 billion, spread over 13 years. That was the largest public works project in U.S. history.

The vision was massive:

• to Connect cities for commerce, Enable quick evacuation in emergencies. and/or national security, and most importantly .

• it would Standardize road signage and quality control across the country.>

->>> I saw a sign 

[Segment 4 – Design and Standards]

Interstate highways follow strict design rules.

First off, every highway in the interstate system is designated by the red white and blue sign, usually with the state name in caps on top .

Here’s what you can expect on an interstate highway:

• Minimum of two lanes in each direction,

• 12-foot wide lanes with shoulders on both sides.

• Limited access, meaning no stoplights or cross traffic.. And what actually qualifies in my and many definition as a true “freeway.”

• interchanges That are grade- separated  (which means ramps and overpasses).

…and speed limits! .

<Are you old enough to remember the maximum 55 mph? My very first car had “55” printed in a different color on the speedometer — like it was some kind of sacred line you weren’t supposed to cross. 

But here’s something most people don’t realize: when the Interstate system was established in 1956, there actually was no federally mandated speed limit. States set their own — and in some rural places like Montana or Nevada, that meant no daytime speed limit at all. Just a general “reasonable and prudent” rule.

That all changed in 1974, during the oil crisis, when the federal government imposed a national maximum speed limit of 55 mph in an effort to conserve fuel. It was a bold move — and pretty controversial at the time.

The fuel savings didn’t exactly blow anyone away. Estimates suggested less than 1% actual reduction. But the safety benefits? Those were clear.

In the first year alone, traffic fatalities dropped by over 16% — from more than 54,000 deaths in 1973 to just over 45,000 in 1974.

So while the fuel logic didn’t quite add up, the life-saving impact made a strong case.

Over time, though, the pushback grew — and in 1987, Congress started allowing 65 mph on rural Interstates. Then in 1995, the national speed limit was fully repealed, and the power returned to the states.

Today, we’re back to a patchwork — >

some states still cap at 65 or 70, while others like Texas and Utah post limits as high as 80 mph in certain areas.

[Segment 5 – Nummbering the Interstates]

Now that we had a national network, it needed a national numbering system—one that wouldn’t conflict with the U.S. Highways already in place.

Here’s how the interstates are numbered:

• Even numbers run east to west, increasing from south to north.

• Odd numbers run north to south, increasing from west to east.

***So I-10 runs along the southern border, while I-94 hugs the northern U.S.

I-5 runs up the west coast, while I-95 hugs the east.

(Music)

 Major interstates end in numbers divisible by 5 - 0 or 5—these are the big, cross-country routes:

• I-10, I-40, I-70, I-80, and I-90.

• Or I-5, I-15, I-35, I-75, I-95.

Routes that don’t end in 0 or 5—like I-17 in Phoenix or , I-29 through Kansas City MO are considered minor interstates, often shorter or more regional.

And that brings us back to our mystery: why no I-50 or I-60?

Because US-50 and US-60 already exist. To avoid confusion—especially when two similar routes might run parallel in the same region—the numbers 50 and 60 were skipped entirely from the interstate list.

[Segment 6 – Three-Digit Interstates: Loops and Spurs]

Now what about 3 digit interstates? 

This is where, especially growing up in SoCal, I never really understood 

And another side note - the naming of freeways starting with @the” is apparently a strictly SoCal thing that will be reserved for a future episode or in depth video no my YouTube channel ..

Well, to make it absolutely clear, just because a highway is “called” an interstate doesn't mean it actually runs into multiple states, and we unofficially call these “intrastate “ highways though they are officially part of the interstate highway system, with all the standards I've already detailed. 

Here’s are the general rules for 3 digit interstates :

• The last two digits tell you which main interstate they branch off from.

these… the 710 to Long Beach, 605 through my San Gabriel valley and the 405 from the valley to South Orange County- all interstate highways. 

• The first digit tells you if it’s a loop or a spur:

• If it’s even, it’s a loop—it reconnects to the same highway. 

• If it’s odd, it’s a spur—it dead-ends in a city or business district.

again 605 doesn't make sense to me 

Nor does the 210

Nor does the lIE, 495 in new York 

Other states seem to have done a lot better with the rules than NY and California - 

A

2. I-275 (Tampa, FL): A loop around Tampa Bay, linking back to I-75.

3. I-195 (Rhode Island): A spur connecting Providence to Cape Cod.

Fun fact: the shortest signed interstate in America is I-375 in Detroit. It’s less than a mile long—a tiny spur that delivers you straight into downtown.

Also, some three-digit numbers exist in multiple states.

I-295, for example, exists in:

• New Jersey (around Trenton),

• Florida (Jacksonville),

• Maine (Portland area).

Each connects to I-95 but serves a completely different region.

[Segment 7 – Rule Breakers and Exceptions]

Not every highway follows the rules.

• I-99 in Pennsylvania was created out of sequence—placed between I-79 and I-81—but numbered purely due to a political push from a local congressman.

• I-238 in California doesn’t even make sense—there’s no I-38, so how can there be a 238? It’s a leftover from when CA-238 was upgraded to interstate status, and they didn’t want to renumber everything around it.

And what about names?

This seems to be another primarily California and Ny thing - 

405 San Diego freeway

10 is the Santa Monica or San Bernardino fwy

In my

• I-495 = Long Island Expressway

And 295 is cross Bronx expy.. 

Where as the rest of the country just says .. 

I-5 , I-65, I-95, you get the point 

• though In Texas, I-35 is sometimes just called “Main Street” by locals

[Segment 8 – State Highways, County Roads, and Farm Routes]

So what about the rest of the highways aside from interstates? 

(Aside from all the different types, each state has different systems and standards .. clearly don't have time to go into: so I'll just touch on…

• State highways are numbered and maintained by individual states… and usually have lots of exceptions to their seemingly nonsense rules. 

• County roads are local—quality varies wildly, and in rural areas, they may be unpaved.

• Farm-to-Market Roads (FM) in Texas were built to connect agricultural land to urban centers. FM roads like FM 1960 or FM 529 near Houston are practically full freeways now.)

Literally runs out of time . Instead check out the episode 13 page and my new daily video shorts on YouTube @masterinthe commute.

[Closing / Call to Action]

So the next time you’re cruising down a highway and you see a sign, ask yourself:

• Am I on a major or a minor interstate?

• Is this a spur, a loop, or a cross-country lifeline?

• And hey, where’s I-50 again?

If you want to dig deeper, check out the Episode 13 page on our website.

I’ve loaded it up with maps, videos, links, and extra info—the kind of rabbit hole that’s worth getting lost in.

And if you’ve got your own story about a highway mystery—or a sign that’s always confused you—email me at freewaytrafficexpert [at] gmail [dot] com.

subscirbe etc..: