Photo Source: Google Maps
By Robert Nowinski and Reed Richards
Most people drive, most people hate traffic, and most people that drive and hate traffic have gone over a cloverleaf interchange in their life. Now when you do go over these, you probably see no problem with them. They let you go from one road to another and smoothly turn without slowing down too much. But, there is a dark side to these seemingly innocent interchanges. Cloverleafs have a few major problems that make them unreliable with heavy traffic and cause merging problems, along with being quite ugly and taking up too much space.
The principal disadvantages of the cloverleaf, according to the Missouri Department of Transportation, are the additional travel distance for the left-turning traffic, the weaving maneuver generated, the very short weaving length available, and the relatively large right-of-way area needed. They also cost more money than a diamond interchange, which is an interchange that could be a good replacement. Traffic flow is an important part of a good intersection and the cloverleaf fails in this regard. On a two lane freeway, a cloverleaf going into that will clog the lanes in high traffic because of the right lane having to weave into oncoming traffic or forcing the right lane to merge into the left, which can also be dangerous.
Cloverleafs also have major environmental problems. You turn at near freeway speeds, so the curves need to be rather large to accommodate larger vehicles to avoid tipping. The area that these interchanges take up can include greenery and plants that house small animals which are at a major risk living in these high traffic areas.
Runoff is also a factor. If the ramp does not have proper drainage, stuff from cars, such as oil, could get into the ground. Fortunately, the height of the side barriers means most of it is negated. Also, erosion can be a concern, but it typically is negligible since it takes a long time for it to happen.
A diamond is a possible replacement as seen above. Overall it’s better for navigation, eliminates last-minute lane changes, and improves sight distance at turns, which leads to fewer crashes. It also is more simple since it has fewer turns and takes up a lot less space, which leads to a reduction in animal risk. Also, it’s closer to the freeway, which leads to faster freeway access.
Urban design is a complex and expensive problem and innovations in freeway design are not necessarily the way to go. We could get rid of thousands of cloverleafs and make driving on the freeway easy, but that would just incentivize people to drive more which creates its own group of problems. Public transportation and shorter commute times would eliminate the construction of any more cloverleafs and defeat the evil forever.
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