The Big Problem With Cloverleaf Interchanges - Cheddar Explains

it's been called a hair-raising motorist mosh pit a traffic generator an abomination to free-flowing cars but once upon a time it was heralded as a miracle of design that would allow drivers to seamlessly merge on and off highways with the greatest of ease you might not know what they're called but you've probably driven on one and they're actually hated most by urban planners this is why this is a cloverleaf interchange they were built to allow two highways to cross without the need for traffic lights or even harsh left or right turns the advantage of the design was that drivers could turn from one road to another without stopping and without having to make a left turn across the path of oncoming traffic with a cloverleaf drivers transition left by swinging right on the circular loop under an overpass there are some definite benefits to the cloverleaf it has a relatively low construction cost because only one bridge needs to be built other interchanges like the directional interchange require many more bridges ramping up the cost significantly clover leafs can be easily upgraded by realigning slip roads which are those roads you speed up on to get on the highway and if you make a wrong turn it's easy to correct by just going around the circles cloverleaf interchanges were built for a world where land is cheap and bridges are expensive and by that i mean the 1920s new jersey roadways back then were atrocious traffic density was 10 times the national average because of cars commuting between new york and philadelphia it was a huge economic problem that government officials were eager to fix traffic was of course heaviest where two roads meet and at the time efficient highway interchanges simply didn't exist edward delano an engineer who worked at the pennsylvania based contracting firm rudolph and delano saw an illustration of a planned cloverleaf interchange in argentina on the cover of an engineering journal the light bulb went off that interchange would be perfect for the overused roads of woodbridge new jersey delano brought the design to government officials and because the traffic was so high they agreed to test the innovative design the woodbridge cloverleaf was hailed as an outstanding development in traffic engineering on the cover of the november 1931 issue of engineering news record it beat out the hoover dam which was banished to the back pages of the same issue cloverleaf interchanges began sprouting up all over the country governments loved them because they were cheap and fix the obvious traffic problems but the same problem that created the cloverleaf was going to become its downfall over the next 40 years the amount of cars on american roads increased by 600 percent the federal highway act of 1956 which created the massive interstate highway system paved the way for a massive increase in drivers which clogged american roadways and this increase exposed the biggest flaw in cloverleaf design notice how these two roads which are where traffic enter are placed before the exit loops this means that drivers are trying to merge into the lanes at the same place that other drivers are trying to merge to exit this traffic conflict called weaving severely limits capacity and causes huge backups into the leaves the buildup of congestion in the leaves causes another problem accidents new jersey transportation department records show that from 1992 to 1994 123 accidents were recorded at the woodbridge cloverleaf a hundred of those accidents were fender benders involving cars going in the same direction indicating an attempted merger that failed a 1999 study by the virginia department of transportation concluded that cloverleafs have the most fixed object accidents of any interchange design the study said that these accidents usually happen when a driver is forced off the road and into a wall or tree in a battle to merge with other drivers it also showed that cloverleaf interchanges were overfilled when traffic surpassed a thousand vehicles an hour during peak rush hours a cloverleaf intersection between the riverside freeway and the pomona freeway in virginia carried about 14 600 vehicles per hour in each direction and because of all this traffic governments are upgrading them which costs a lot of money the same cloverleaf interchange in virginia was rebuilt for approximately 320 million dollars clover leafs were made in a world where land was cheap and building bridges was expensive but now land is expensive and building bridges is slightly less expensive once upon a time clover leafs could have been fixed by making the loops bigger but now all of that land is taken up and engineers have to construct expensive tunnels and flyover bridges to remedy the tight loops take a look at this reconstruction project in ohio at the i-270 to route 161 interchange the cloverleaf built in the 1960s caused numerous accidents and lots of traffic to fix this problem engineers eliminated three of the four ramps by constructing a tunnel from the west to the south and a flyover ramp from the 270 southbound to the eastbound they constructed another flyover ramp and left the last loop intact the construction of these two flyover ramps and a tunnel in 2007 cost 134 million dollars even the first cloverleaf in the country in woodbridge wasn't safe from being updated in 1998 the new jersey department of transportation announced they were going to start a 68 million dollar project to reconstruct the interchange they added a new loop twice as big as the original which involved acquiring the land around it a large expense building longer ramps to new street-level intersections and added merger lanes this is what it used to look like and this is what it looks like today part of the reason why clover leafs are being built less now is because of space if you play city skylines you'll know just how much space they take up the dead space within each leaf takes up a lot of land and if you try to reduce that excess it makes tighter loops which increases traffic and the likelihood of accidents where city planners may have once built cloverleaf interchanges they're now building different more efficient types of interchanges today engineers are more likely to choose either a diamond directional or stack interchange diamond interchanges are best suited for areas where land is limited and traffic volume is high cities with a higher budget and more traffic tend to choose directional interchanges that being said the cloverleaf interchange still can be the best option in certain situations clover leafs in spacious rural areas continue to work rather efficiently due to a lower traffic density [Music] but in most places it just doesn't make sense and it's a problem that not all american cities can afford to fix it's another visible symptom of america's infrastructure woes in 2019 the american society of civil engineers gave the u.s a d-plus grade on their infrastructure this is mainly because most of our large roads and bridges were built over 50 years ago engineers could have never anticipated the massive boom in population and vehicle use according to the asce our roads were never meant to be used this much and to last this long the asce predicts that it would take over 4.6 trillion dollars to improve our infrastructure over the next decade it doesn't look like that's going to happen so you can plan on seeing more potholes but maybe plan on seeing slightly less cloverleaf interchanges if you like this video make sure you like comment and subscribe and don't forget to ring the bell for post notifications we'll see you next [Music] time

Channel: Cheddar

Views: 961,650

Rating: 4.7869792 out of 5

Keywords: Cheddar, cheddar explains, urban planning, highways, highway interchange, interchange, interchanges, cities skylines, directional interchange, stack interchange, diamond interchange, roads, streets, street design, city planning, architecture, turnpike, interstate system, traffic, roundabout, rotary, cloverleaf interchange, cloverleaf, exit ramp, infrastructure, american infrastructure, cities, freewway, highway, car accidents, cars

Id: 7GTZRSPry70

Length: 10min 1sec (601 seconds)

Published: Thu Jul 16 2020