Ever wonder why a road curves or tilts a certain way? Discover the hidden physics and safety rules engineers use to keep traffic flowing smoothly.
A well-designed intersection—whether it’s a perfectly angled T-junction or a high-tech RCUT—is designed to make sure those human mistakes don't result in human tragedies.
How intersections, bridges, etc are designed in a city
Intersections are ideally placed on straight, flat sections of road to maximize safety and physics-based control. If an intersection must be on a curve, engineers limit the "superelevation" (the tilt of the road) to 0.04 or less to ensure cars stay on the road while turning. Similarly, they aim for a "grade" or slope of no more than 3 percent so that drivers can come to a safe stop without the interference of steep inclines or declines.
When designing the radius of a turn, engineers consider two types of vehicles. The Design Vehicle, such as a standard delivery truck, is expected to make a turn perfectly within its designated lane. The Check Vehicle, typically a much larger semi-trailer like a WB-62, is allowed a "Degree of Encroachment," meaning it is permitted to swing wide into adjacent lanes during a turn as long as it doesn't drive over the curb or cause a total traffic meltdown.
Modern roundabouts use "deflection" to force drivers to slow down to 15–25 miles per hour, creating a self-enforcing speed limit. Unlike traditional intersections where high-speed "T-bone" or head-on collisions can occur, the circular geometry ensures that any accidents are typically low-speed sideswipes. Additionally, roundabouts use "truck aprons"—textured inner rings—that allow large vehicles to navigate the turn while keeping the path narrow enough to slow down smaller passenger cars.
An RCUT, or Restricted Crossing U-Turn, is a design that eliminates dangerous left turns and straight-across movements from side roads onto busy highways. Instead, drivers must turn right and then perform a U-turn at a dedicated "loon" (a paved bulb-out) further down the road. This replaces high-conflict "gap of death" maneuvers with safer, same-direction movements and allows the main highway to have longer green lights, significantly increasing traffic flow.
Engineers use several geometric features to protect those not in cars, such as "curb extensions" or "bulb-outs" that shorten the distance a pedestrian has to walk across the street. They also design "refuge islands" at least 8 feet wide on high-speed roads to provide a safe space for people with strollers or bikes. Furthermore, sight lines are strictly managed to ensure drivers can see the actual ground (height of object at zero) rather than just the tops of other cars, making shorter pedestrians like children more visible.
From Columbia University alumni | built in San Francisco
avg rating
7.84k+ App Rating
BeFreed Community
Seriously I haven’t even explored this app fully yet but from using it the last few days I am so impressed... BeFreed is on a different level from any other learning app I have used. This makes it ultra engaging and can actually improve your concentration which is great for all the doom scrollers!
@ladyInfinity
I bought BeFreed exactly 23 days ago, and I have used it every single day since. It has completely embedded itself into my daily workflow and learning habit.
@jayallen
The truth is, the app has exceeded all my expectations. I can ask it to generate audio on any topic, whatever it may be, and the result is impressive. My professional field is a specialization in psychotherapy and it is multidisciplinary; however, the answers are very accurate.
@Raguipa
What I appreciate most is how much it's reduced my scrolling – I'm spending less time searching and more time absorbing information. The combination of full audiobooks, podcasts, the learning plans are brilliant.
@colonyofcreatorsNGO
I have been a PhotoReading Accelerated Learning Instructor for the past 24 years... books and reading and learning are my thing, and BeFreed has done a great job in providing an innovative approach to disseminating and delivering information in an easy to consume way.
@BeFreed user
It is not just a book summary app, I have used the 'fun reading' option and it's a much better summary and way to grasp ideas the traditional way, that alone is worth this deal.
@austinakon
I love this app. Used it for several days and I cannot stop listening. Such a great way to start.
@jcrules328
I really like the program; I have already tested it for around one month, and I feel that it's an amazing gem. It works so well because I can use BeFreed to create my own topics, and the voice is so good with unlimited choice of narrations.
@DanielCZ
I love the fact that I can get useful, condensed, information and ideas in a 8 - 15 minute podcast style audio. I'm not a general fan of podcasts because of all the fluff, but this cuts through all that.
@BeFreed user
I am finishing up my doctorate, and have to read a lot of unfamiliar material... With BeFreed, you simply enter a prompt, and the app finds source material for you and generates an audio podcast. I find the process in BeFreed to be more streamlined than NotebookLM.
@Brad
I often search YouTube for something to listen to whilst making breakfast, when I'm out walking, commuting, etc, and BeFreed has provided an even more targeted approach, without the adverts and the fluff!
@BeFreed user
The absolute best part about this platform is its versatility. There is literally no subject that is off-topic. It handles whatever you throw at it... It is rare to find an learning tool with zero limitations that actually delivers on its promises.
@jayallen
BeFreed is fantastic. The user-friendly design means I spend less time navigating and more time learning. The mix of audiobooks, podcasts, and learning plans is a genius combo that has completely changed my daily routine.
@BeFreed user
At the start I needed a while to understand how to create podcasts in italian language and boom! It is so great! I can ask to explain every argument and it does so well and so smartly!
@matteo77
BeFreed has become my daily app for audio books tools... What I like the most is the way you put your text and come with an audio that you can listen on the go.
@kotanzu1
This plan is essential for urban planners, architects, and community leaders who want to move beyond technical engineering toward human-centric design. It offers a critical framework for understanding how the built environment can either bridge or widen social divides in modern cities.
Understanding how engines work is essential for anyone interested in automotive technology, mechanical engineering, or simply wanting to know what happens under the hood of their vehicle. This knowledge is valuable for aspiring mechanics, engineering students, car enthusiasts, and professionals in transportation industries who need to grasp both the practical and theoretical aspects of engine operation.
Vehicle crash biomechanics is critical for professionals working in automotive safety, accident reconstruction, trauma medicine, and injury prevention. This interdisciplinary field combines physics, engineering, and medical science to understand how collisions cause injuries and how to prevent them. It's essential for automotive engineers, forensic specialists, emergency responders, safety researchers, and anyone involved in designing safer vehicles or investigating crash-related trauma.
This learning plan provides a comprehensive overview of how human design has shaped our world across centuries. It is ideal for aspiring architects, history enthusiasts, and urban planners looking to understand the structural and spiritual evolution of our cities.
This learning plan bridges the gap between high-level fluid dynamics and real-time competitive logic. It is ideal for aspiring engineers, data analysts, or dedicated fans who want to understand the technical and historical forces that define modern Grand Prix racing.
This plan provides a deep dive into the engineering and human operations that power modern refineries. It is ideal for aspiring chemical engineers, energy sector professionals, or anyone curious about the industrial backbone of the modern world.
In an era of information overload, understanding the hidden forces behind our decisions is a critical superpower. This plan is ideal for professionals, investors, and students looking to bridge the gap between abstract logic and the messy reality of human behavior.
This plan offers a rare holistic approach to the STEM fields by bridging the gap between abstract thought and physical application. It is ideal for students, aspiring engineers, and curious minds who want to understand not just 'how' things work, but the deep 'why' behind the laws of nature.
