How Are Highways Designed?

Exploring the relationship between speed, safety, and geometry of roadways.

Although many of us are regular drivers, we rarely put much thought into roads. That’s on purpose. If you’re thinking about the roadway itself at all while you’re driving, it’s probably because it was poorly designed. There are so many factors that go into highway safety, many of which are more philosophical or psychological than pure physics and engineering. But to a certain extent, highway design is an art form.

Writing/Editing/Production: Grady Hillhouse
Editing and Direction Help: Wesley Crump

This video is sponsored by Ting.

[bobthudpucker]

True story:
Where I live, the main street is perfectly straight the whole way through the town. It used to have a speed limit of 40 MPH. Then a family whose house was right on Main Street complained about the speed and asked the city if they could lower it. The city looked into it... and changed it to 45 MPH.

[zan]

In Australia where I live, potholes and kangaroos determine highway speedlimits.

Actually almost crashed into a kangaroo whilst passing over a crest as it appeared out of nowhere, just like you said. Thats why I always slow down when I'm going over crests or around tight corners where my sight distance is impeded. It surprises me how fast many people go when they are literally driving blind around these bends/curves.

[jordyhellemons]

This man can make anything interesting.
He single-handedly brought back my interest in learning about engineering.
Legend

[spikeevans]

I recall, as a young engineer in the '70s, being told that interstates were designed to hide changes of direction at the crest of slopes to make the road appear straight.
Also one of my pet peeves with modern highways are the spirals on exit ramps that sneak up on the driver and all of a sudden they are going too fast; a big problem on a motorcycle.

[BiffaPlaysCitiesSkylines]

I found this extremely interesting :-)

[SunlightAldo]

"Not many people think about roads"
Me: *a loyal subscriber with post notifications who pesters my friends about why theres cracks in side walks and about all the layers that go into road construction*

[blakebiermann]

Lane widening in curves is also very helpful when you're pulling a long trailer or driving something wide. Less chance of less skilled drivers getting too close to you

[mark-ish]

9:17
Draws a perfect moose/deer, contrasted with a brick "car" 😄

[EstebanFelipe]

Practical Engineering: There are many factors that come into play when designing a highway

My city: We don't do that here

[jonescg]

I'd love to hear more about railroad engineering - how are new railroad formations settled on? And how do they get the transitions and radii just right? I reckon that would be a fantastic video. Keep up the great work!

[TheAssassin]

This Traffic Engineer approves this video. although i must mention that set speed limits are mostly political.

[andrebartels]

I never cared about civil engineering until I found your channel. Now I gradually start to see the world I live in with different eyes. Thank you for widening my horizon 👍

[MukulVyas]

I'm a Civil Engineering graduate and due to a monotonous, quality lacking, banal and unfair education system and working culture, I've lost interest but your channel keeps me motivated. Thank you so much :) I wish I had a teacher like you. This is how Civil Engineering should be taught.
Thank you once again. :)

[rnrtruestories]

man i love your channel. I worked on the design side for almost 10 years for roads and bridges.

[visi]

As an ex-Road engineer, great video! you covered up the basics very well! Just another thing to add, the transition length for straight to curve is also dependent on the transition length required to transition from crown to Super elevation.

[rogerwilco]

Hills?
What is this magic you're talking about?
- The Dutch.

[TheOfficialCzex]

Engineer: "... So, anyway, the most effective speed limit for this section of highway is 75 MPH."

The State of Virginia: "35 it is then!"

[doggetay]

4:37 "If the superelevation angle is just right, and you're traveling at a right speed, your cup of coffee won't spill around the bend"

EUROBEAT INTENSIFIES

[ionmaster]

Practical Engineering: How are highways designed?
Cities Skylines players: Write that down! Write that down!

[stupidburp]

I noticed that the Autobahn in Germany had much longer on and off ramps, gentler curves, more reflectors on the sides, more signage, and a smoother road surface with less pooled water than I was used to from driving in the USA. It showed me that the details of how the roadway was designed could help safely enable faster typical speeds with fewer accidents. I have heard that the driver training in Germany is also more in depth and strict than in the USA which may also contribute to safety.