WEBVTT - What Do the Numbers on Interstate Signs Mean?

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<v Speaker 1>Welcome to brain Stuff production of I Heart Radio Pay

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<v Speaker 1>brain Stuff Lauren Boba blam here. If you've ever driven

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<v Speaker 1>west on Interstate A D through Nebraska, you've seen one

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<v Speaker 1>of the flattest and emptiest roads in America, and you

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<v Speaker 1>probably had some time to ponder life's most important questions.

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<v Speaker 1>For example, why is the highway called I A D anyway?

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<v Speaker 1>And why do different interstate names contain one or two

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<v Speaker 1>or three digits. Well, buckle up, because you're about to

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<v Speaker 1>learn about the codes behind the US interstate naming system.

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<v Speaker 1>But for starters, let's talk about how the interstate highway

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<v Speaker 1>system began. The formal name for these roadways is the

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<v Speaker 1>Dwight D. Eisenhower National System of Interstate and Defense Highways,

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<v Speaker 1>and the project was approved by Congress through the Federal

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<v Speaker 1>Aid Highway Act of ninety six that authorized the construction

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<v Speaker 1>of about forty one thousand miles or sixty six thousand

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<v Speaker 1>kilometers of highways stretching across the country from east to

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<v Speaker 1>west and north to south. One of the main purposes

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<v Speaker 1>of the interstate system was national defense. President Eisenhower had

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<v Speaker 1>served as the Supreme Commander of Allied Forces during World

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<v Speaker 1>War Two. In Europe and had witnessed the importance of

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<v Speaker 1>Germany's Autobahn network, which allowed for speedy transportation throughout the country.

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<v Speaker 1>Another slightly more ominous selling point the quick evacuation of

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<v Speaker 1>cities in the case of potential nuclear attacks. And of course,

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<v Speaker 1>the system was touted as a way for all Americans

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<v Speaker 1>to travel with fewer traffic jams and more efficient routes

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<v Speaker 1>with no at grade crossings, that is, intersections. The system

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<v Speaker 1>used overpasses and underpasses to allow for seamless, stop free,

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<v Speaker 1>high speed travel. There are now forty six thousand, eight

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<v Speaker 1>hundred and seventy six miles or seventy thousand, four hundred

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<v Speaker 1>and thirty nine kilometers of roadway within the interstate designation.

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<v Speaker 1>Construction began in nineteen fifty six in Missouri on what's

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<v Speaker 1>out named I seventy, but the system as a whole

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<v Speaker 1>wasn't completed until when crews finished a devilishly difficult stretch

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<v Speaker 1>in Glenwood Canyon, Colorado. There you'll find forty bridges and

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<v Speaker 1>viaducts on a single twelve mile or nineteen kilometer stretch.

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<v Speaker 1>The Interstate Highway System transformed American life. The cargo trucking

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<v Speaker 1>industry arose, gas stations and truck stops, blossomed, suburbs sprung

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<v Speaker 1>up around cities, and the concept of the road trip

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<v Speaker 1>entered the national lexicon. And as those road trippers zipped along,

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<v Speaker 1>some of them surely wondered why interstates have various numbering systems.

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<v Speaker 1>But why is one named I five while another is

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<v Speaker 1>I four eighty. Let's take a closer look at the

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<v Speaker 1>digits on those shield shaped white, red and blue signs.

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<v Speaker 1>The number of digits in the name tells you whether

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<v Speaker 1>an interstate connects more than one city, or if it

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<v Speaker 1>serves a single metropolitan area. Interstates with one or two

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<v Speaker 1>digits all interconnect several regions. Those with three digits, like

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<v Speaker 1>I to eighty five, on the other hand, are meant

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<v Speaker 1>to serve a single city and are called auxiliary interstate highways.

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<v Speaker 1>They connect to longer two digit highways. The last two

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<v Speaker 1>digits match the parent highway. For example, I four e

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<v Speaker 1>d in Omaha is a five mile stretch that connects

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<v Speaker 1>I e ight in Nebraska with I twenty nine in Iowa. Likewise,

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<v Speaker 1>the aforementioned I T eighty five circles Atlanta and connects

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<v Speaker 1>to I eight five going north and south. Continuing to

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<v Speaker 1>use that as an example, you can tell that I

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<v Speaker 1>A D five runs north to south because odd numbered

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<v Speaker 1>interstates move traffic north to south, while those with even

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<v Speaker 1>numbers stretch east to west. The numbering for east west

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<v Speaker 1>highways starts in the south and moves north, so I

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<v Speaker 1>ten anchors the bottom border Santa Monica, California, to Jacksonville, Florida,

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<v Speaker 1>and I ninety is near the country's northern border, a

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<v Speaker 1>Seattle to Boston. Meanwhile, for north to south running interstates,

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<v Speaker 1>numbering begins in the west, starting with I five parallel

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<v Speaker 1>to the west coast. The easternmost interstate is I N five,

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<v Speaker 1>running on the east coast from Maine to Miami. There

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<v Speaker 1>are some rare exceptions to this pattern in cases where

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<v Speaker 1>stretches of road were added after the first framework was

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<v Speaker 1>already in place. For example, I N nine didn't receive

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<v Speaker 1>its interstate designation until and so it lies to the

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<v Speaker 1>west of There are only two places across the country

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<v Speaker 1>where interstates split as they moved through major cities, both

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<v Speaker 1>on I thirty five, one around the Minneapolis St. Paul

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<v Speaker 1>metro area and the other to go through Dallas and

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<v Speaker 1>Fort Worth. Meanwhile, the first digit of a three digit

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<v Speaker 1>interstate tips you off to its purpose. Connectors or spurs

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<v Speaker 1>that only intersect one time mostly receive odd numbered first digits.

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<v Speaker 1>Even numbered first digits, how ever, tend to be bypasses

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<v Speaker 1>and loops that intersect with their parent interstate in two locations.

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<v Speaker 1>The names of major interstates are never repeated. They're always unique. However,

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<v Speaker 1>some lesser stretches do use the same two digit numbers.

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<v Speaker 1>For example, both New York and North Carolina have an

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<v Speaker 1>I eighty seven. There are also I seventy six is

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<v Speaker 1>in both Colorado and Pennsylvania. Three digit interstates, however, can

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<v Speaker 1>be used as often as necessary throughout the country, although

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<v Speaker 1>they can't be repeated in a single state. But this

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<v Speaker 1>numerical interstate system can get even messier. For instance, in

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<v Speaker 1>San Francisco, there's I to thirty eight, even though there's

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<v Speaker 1>no I thirty eight for it to connect to. Instead,

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<v Speaker 1>it's an artery between I e eighty and I five eight.

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<v Speaker 1>But because California already had so many roads, the more

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<v Speaker 1>appropriate digits were already in use with other roadways, and

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<v Speaker 1>there are other exceptions to Alaska, y E, and Puerto

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<v Speaker 1>Rico all have interstates Even though these roads don't connect

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<v Speaker 1>to other states, they have special lettered designations. Alaska has

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<v Speaker 1>A one through A four Hawaii and H one through

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<v Speaker 1>H three in Puerto Rico PR one and PR two,

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<v Speaker 1>and state highway naming convention differs a bit from the interstates.

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<v Speaker 1>These roadways, which are denoted by black and white signs

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<v Speaker 1>with badge symbols, use the same system of odd numbers

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<v Speaker 1>for north south routes and even numbers for east west routes. However,

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<v Speaker 1>the number system is flip flopped. The numbers on east

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<v Speaker 1>west roads gets smaller as you go from south to north,

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<v Speaker 1>and the numbers on north south highways increase as you

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<v Speaker 1>go from east to west across the state. Meanwhile, I

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<v Speaker 1>ninety is the longest U S inter state, stretching all

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<v Speaker 1>the way from Boston to Seattle and covering nearly three thousand,

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<v Speaker 1>one hundred miles or five thousand kilometers, traverses thirteen states,

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<v Speaker 1>and I, which connects Miami to Maine, cuts through the

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<v Speaker 1>most states of all the Inner States fifteen, and it

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<v Speaker 1>also goes through Washington, d C. Today's episode was written

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<v Speaker 1>by Natan Chandler and produced by Tyler clang Or. More

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<v Speaker 1>on this and lots of other numerous topics. Visit how

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