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It’s really just four lanes, a median, and some on and off ramps.
The Interstate Highway system is no engineering marvel, no unprecedented undertaking, no massively
innovative concept.
It’s a simple idea—one that arose since the earliest days of the automobile.
It’s not exciting, which is why it often goes so under appreciated.
Take the Interstates away, though, and you have a weaker nation.
You have one with dramatically starker regional divides, one with increased decentralization—more
specifically, you have a nation absent of a noticeable portion of the late 1900s economic
development and transformation.
These words, like the system itself, still aren’t exciting, but put more simply: if
you are an American, regardless of whether you use the Interstate system, your life would
be noticeably different in a reality without the Interstates.
It’s a single collection of roadways, with an influence so great that it permeates into
every American’s life.
It all started here, 102 years ago.
79 vehicles departed from the White House’s Ellipse at 11:15 AM on July 7th, 1919.
They snaked through the District’s streets before crossing into Maryland and stopping
for lunch in Rockville at 12:30 PM.
The coupling on one of their kitchen trailers broke and a car’s fan belt too, but all
in all, it was an uneventful 7 hour, 46 mile, 74 kilometer journey to the Frederick Fair
Grounds.
12 and a half hours later, they woke up, left, drove, arrived, and slept again.
This cycle repeated itself.
Day after day, they cut 40 or 50 or 60 miles deeper into their westward journey.
The convoy climbed through the heights of the Appalachian mountains, trekked through
the mud of Ohio, before crossing the Mississippi River at 4:10 PM on July 22nd.
From there, they entered an area defined by desolation.
Few dared venture west in a motor vehicle in 1919—always opting for the relative comfort
and speed of passenger trains.
This convoy, though, was making the journey specifically to determine just how difficult
this feat was—to what extent such a journey was feasible for military logistics purposes.
The answer came quickly.
Despite routing themselves on the most developed transcontinental road of the time, the Lincoln
Highway, they constantly had to divert around disrepair, physically disassemble covered
bridges to get their trucks through, and fight physics on roads too narrow for an oncoming
car to pass.
Gas stations were few and far between, so such travel required truly expedition-level
planning.
Each time they entered a city, though, they were greeted by hoards of intrigued locals
and dignitaries, but those crowds thinned as the convoy crawled further into the desolate
west.
Most, but certainly not all, of their vehicles successfully traversed the Rockies, and the
same can be said for their trip across some of the Lincoln Highway’s roughest roads
in Utah.
With time, though, the trend reversed, roads improved, and they finally saw pavement again
as the convoy entered California—its final state.
After a final evening in Oakland, California, the vehicles loaded onto a ferry, crossed
the bay, and made a ceremonious arrival in San Francisco accompanied by a massive parade
and a formal dinner.
That was September 6, 1919—62 days after their departure from the White House Ellipse.
Having concentrated nearly all their waking hours on driving, the math works out to an
average travel speed of just 5.65 miles or 9 kilometers per hour—a staggeringly slow
pace on a road branded as a highway, in a year featuring technologies such as electric
refrigerators, airplanes, and long-distance phone service.
The convoy accomplished its mission of appraising the feasibility of this route for more practical
military purposes, but the report back to Washington was not positive.
One Lieutenant Colonel, tasked with observing the journey, wrote, “Extended trips by trucks
through the middle western part of the United States are impractical until the roads are
improved, and then only a light truck should be used on long hauls.”
It was clear that, for now, until roads were improved, transcontinental motor vehicle trips
would remain the domain of publicity stunts and enthusiasts.
But then the years started passing.
Administration after administration, observing the growing presence of motor vehicles in
the lives of increasingly everyday Americans, recognized that road construction was not
something that could be left the responsibility of states.
While individual states did make plenty of progress building high quality urban and rural
roads, their interests were insular.
Iowa, for example, would have no interest building a highway with the primary purpose
of connecting Illinois to Nebraska.
As Americans went off to fight in Europe during World War Two, they observed the efficiency
of Germany’s national Reichsautobahn highway system, but when they returned home, they
were forced to navigate a patchwork of state systems of varying quality to get anywhere
beyond their local areas.
In the 1950s, when America was a mere decade out from landing men on the moon, it still
took significant planning and the better part of 10 days to reasonably traverse from one
coast to the other.
While this might have been inconvenient for road-tripping Americans, it mostly meant that
there were regions that simply could not compete with coastal areas in the industrial sector
due to high transport costs and times.
It was clear something had to change, but efforts to increase highway construction at
the federal level were constantly stalled by funding issues and a general lack of volition.
But then came someone new.
One of the members of 1919 transcontinental convoy, in fact, the very Lieutenant Colonel
who provided the earlier report on the journey to Washington, continued on in his military
career, and rose through the ranks until he became Supreme Allied Commander of the European
theatre in World War Two.
Then, upon return to the US, he entered a political career, culminating with his inauguration
as president on January 20, 1953.
This was, of course, Dwight D Eisenhower.
With the groundwork laid by decades of planning and false starts, Eisenhower’s task was
centered on finally finding the political will and funding to turn this concept map,
a 1955 publication by the Bureau of Public Roads, into reality.
After nearly three years of political maneuvering, he succeeded.
On June 29th, the Federal-Aid Highway Act of 1956 was signed—dedicating some $25 billion
to constructing 41,000 miles or 66,000 kilometers of highway.
Unlike previous attempts at similar programs, the federal government would now pay 90% of
the costs of these Interstate highways, with individual states responsible for the rest—largely
funded by a hike in the federal gas tax.
Just three months after the bill’s signing, paving work began on a section of Interstate
70 in Kansas, and two months after that, the same section opened to the public—representing
the first miles of a system that would engulf the country over the coming decades.
Now, whether it’s I-40 in Tennessee or I-90 through Idaho, the way these roads were built
was highly, highly standardized.
That was, after all, the point.
These standards are codified in a simple eight page document entitled “A Policy on Design
Standards—Interstate System.”
To start with, fundamentally, Interstates must have controlled access—meaning, the
manner in which vehicles enter or exit the roadway must be controlled through on and
off ramps.
That’s why, unlike with many state highways, you never see intersections with stoplights
on Interstates, except when rules are violated.
The standards also set out a minimum speed—50 miles or 80 kilometers per hour or in urban
and mountainous areas, 70 miles or 110 kilometers per hour in rural areas—and maximum grade—up
to 7%, corresponding to 370 feet of elevation gain per mile of road, or 70 meters per kilometer,
depending on speed and topography.
There must be at least two lanes in each direction of travel, 12 feet or 3.5 meters in width,
with a cross slope—essentially, an angle to allow for rain run off—of at least 1.5%
and ideally 2% grade.
Tunnels and bridges must have at least 16 feet or 5 meters of vertical clearance, although
less is allowed through urban areas as long as an alternate route with 16 foot clearance
is available.
Aside from a few smaller details, that’s the entirety of the Interstate highway design
standards.
It’s incredibly simple.
Implementing this nationwide, however, was no simple endeavor.
When the project started, in the 50’s, one mile of Interstate cost some $8.5 million
to construct, or $5.3 million per kilometer, however, through the decades, as labor costs
rose and the simplest sections stood completed, this ramped up to over $34 million per mile,
or $21 million per kilometer.
Unsurprisingly, the Interstate system quickly blew past its original $25 billon budget allocation,
but people and governments were convinced—the project gained more and more funding, and
was reaching completion by the time the 80s turned into the 90s.
To complete the original vision, just one last section remained: a 12.5 mile, 20 kilometer
stretch through Glenwood Canyon, Colorado.
With thousand foot walls flanking on each side, little room exists aside the Colorado
River for a roadway, but a complex collection of bridges and tunnels were constructed at
a cost of $960 million, inflation adjusted, corresponding to $75 million per mile or $47
million per kilometer of roadway.
Once this engineering marvel was completed in 1992, however, the nation was connected,
and more than two decades after his death, Eisenhower’s vision was realized.
His 62-day transcontinental expedition from 1919 now takes a mere 42 hours.
In such a decentralized country, consisting of a patchwork of states each with unique
governments, laws, cultures, and more, the consistency of a nationwide, federal transportation
system is, in and of itself, unique.
It is one of the most regular interactions Americans, especially in far-flung western
and southern regions, might have with a federal program.
Today, the largest urban center located further than 25 miles or 40 kilometers from an Interstate
highway is Fresno, California, with a population of about half a million.
In fact, only 14 cities with over 100,000 people are located further than this distance.
Even Alaska, Hawaii, and Puerto Rico are now included in this program, despite the fact
that their Interstates don’t actually extend Interstate.
With wide lanes, smooth turns, consistent grades, and more, these highways are remarkably
safe.
While nationwide the US averages 1.3 deaths per 100 million vehicle miles travelled, Interstates,
for the same 100 million vehicle miles, observe just 0.55 deaths each year.
Incredibly, that means that, assuming the alternative is equivalent travel on non-Interstate
roads, this system is responsible for saving about 6,500 lives per year.
Beyond the moral component—the innate human desire to preserve life—the US Department
of Transportation, on a statistical basis, values a human life at $11.7 million dollars
when evaluating potential safety standards, so the safety profile of the Interstate Highway
system by itself has a theoretical economic impact of about $75 billion per year—therefore
easily justifying its cost alone.
But then there’s the more direct impacts.
Among the more populated states, construction disproportionately took place in southern
states such as Georgia, South Carolina, or Arkansas on a basis of miles constructed per
capita.
Then, in less populous states, the Interstate disproportionately penetrated the American
west, with states such as Utah, Montana, Nevada, and Wyoming receiving the most miles per capita.
Therefore, it was the South and West that received the greatest impact.
In essence, what these roadways did was connect the US’ economic centers to the periphery,
so the periphery had the most to gain by, effectively, reducing the relative distance
to centers by a factor of 30%, on average.
In the case of Interstate 5, for example, which runs along the entire west coast from
the border to Mexico to that with Canada, California, the state that encompasses the
majority of its distance, actually sees the smallest benefit.
That’s not to say that benefit is small—the removal of the Interstate would correspond
to a 6% loss in overall income in the state—but Oregon, the 12th most sparsely populated state
in the nation, would lose 15% of its income if I-5 simply disappeared.
It’s worth fully considering just how staggering that statistic is—a single, simple four-lane
roadway, stretching some 300 miles or 500 kilometers through Oregon, attributable for
15% of its income.
This does, however, make sense.
Oregon’s economy—significantly undergirded by the natural resources, manufacturing, and
agriculture sectors—is highly trade dependent.
The state does not, however, have any major export ports, so when a manufacturer in Salem,
Oregon, for example, needs to transport finished products to the port of Oakland, it would
likely hire a truck to take the 9-hour journey south on I-5.
The shortest non-Interstate route, however, would take 13 and a half hours on roads with
potentially burdensome weight restrictions, inadequate facilities, low bridges, and other
constraints.
It just makes getting product out harder.
Now, ultimately, transport cost is rarely an enormous portion of a given product’s
cost—a five-cent increase on a $10 product produced further from Oakland isn’t massive—but
that’s not the context that matters in the competition between places for industry.
If the options are between a state that has a conduit enabling lower-cost, reliable, fast
transportation in and out, and all other factors are the same, why would a manufacturer decide
to locate is the more poorly connected place?
The economy is a competition, and in competition, the smallest margins matter, even when they
don’t in a non-competitive context.
Considering the alternate was the status quo—individual states building their own highways, disconnected
from any national program—this program caught the states that couldn’t afford massive
infrastructure projects, many of which were in the South and West, up to the rest.
Therefore, Interstates made these states more competitive by reducing their relative distance
to the rest of the world.
That’s not to say the program was perfect, though.
Just as much as it proved revolutionary to more rural areas, it gutted cities.
Neighborhoods, predominantly poorer ones, were leveled to the ground to make space for
Interstates and their associated infrastructure.
This often created clear, physical barriers between certain neighborhoods and urban centers,
which reduced opportunity in these excluded neighborhoods.
They also had the effect of encouraging reduced density, which increases the environmental
impact of cities, creates scenarios where job opportunity is linked to car ownership,
and additional potential negative impacts.
Altogether, the way in which Interstates interact with cities was often poorly planned and executed.
But when examined in aggregate, the Interstate highway system is one of the best investments
the United States ever made.
While by no means unique to the United States in concept, the vastness and regional disparities
in the country meant such a system had a uniquely powerful impact.
For every dollar spent on the program, it has returned at least six in economic benefit.
In the context of nations, connectivity is power.
Therefore, the reason why the Interstate highway system is the most impactful infrastructure
program in American history is simply because, as of now, it’s the largest.
I definitely enjoy nerding out about the Interstates, and hopefully you now do too, so I made a
whole other video about the strangest, quirkiest sections of the system, like why Interstate
180 exists—just connecting to a town of 700, and travelled on by only about 100 vehicles
per hour—or the town that essentially exists because of one of the only stoplights on an
Interstate.
You can watch that video on Nebula, the streaming site founded by myself and loads of your favorite
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