Cloverleaf Interchanges in NoVa (Chantilly: construction, disposal, dangerous)

[Curbed Enthusiasm]

I know this is kind of a technical engineering question, but why are there still so many cloverleaf interchanges in NoVa? They are such an inefficient, outdated way to move traffic, and totally inappropriate for NoVa's clogged highways. Yet there are still so many, and they don't appear to be getting replaced with more efficient road designs. The Route 123/ I-495 is a perfect example. There's tons of weaving back and forth from the loops on this heavily traveled interchange, and despite all the reconstruction, they kept the old design. In California, Caltrans has replaced most cloverleafs with new interchange designs except for those in lightly traveled areas. Anyone have a guess as to why VA keeps these old cloverleafs interchanges intact?

In case anyone is wondering what a cloverleaf is: Cloverleaf interchange - Wikipedia, the free encyclopedia

[tysonsengineer]

The era in which most of the infrastructure was built in NOVA is really why. You are looking at design standards used in the industry between 1975 and 1995 when major highway projects were largely complete in VA. Specifically the 495 interchanges. Is your particular issue with them the fact that they are both deceleration and acceleration lanes?

Compared to the new Caltran intersections they use far less right of way, which is one reason the federal highway system utilized them in the first place. Staggered flyovers can be seen, for instance look at the newly built Route 28 limited access system, but again those take up way more right of way than equivalent cloverleafs

BTW, this is the wonkiest thread ever created on the subject of transportation. Well played

[spencgr]

Originally Posted by tysonsengineer

BTW, this is the wonkiest thread ever created on the subject of transportation. Well played

Wonky?? No way. There is no way this thread was designed with anyone else but you, TE, to respond. I think they are courting you......

[tysonsengineer]

There are atleast 3000 civil engineers in the NOVA region. I'm sure there must be more people who could have responded... but I think you are right. OH NO. IT MUST BE AN AMBUSH!!

[spencgr]

Originally Posted by tysonsengineer

There are atleast 3000 civil engineers in the NOVA region.

Yes, that may be true.....but only one on NoVa CD.......

[jzcrandall]

An electrical engineer, a mechanical engineer, and a civil engineer are having a debate over who designed the human body. The mechanical engineer says, "it was clearly a mechanical engineer. Who else would design the skeletal and muscular system?" The electrical engineer says, "it was clearly a mechanical engineer. Who else would design the brain and the nervous system?" The civil engineer says, "it was clearly a civil engineer. Who else would think to put a waste disposal system next to a recreational area?"

[snowdenscold]

OK, I'm curious. What are these specific Caltrans interchanges you're referring to and how are they more efficient? I honestly don't know much about the subject.

I do know that in constructing the HOT lanes, they took at least 2 existing cloverleaf interchanges that used to have no traffic lights (Route 7 and Braddock Road), and have put in a traffic light at each one. Isn't that moving in the wrong direction?

[Curbed Enthusiasm]

Originally Posted by snowdenscold

OK, I'm curious. What are these specific Caltrans interchanges you're referring to and how are they more efficient? I honestly don't know much about the subject.

I do know that in constructing the HOT lanes, they took at least 2 existing cloverleaf interchanges that used to have no traffic lights (Route 7 and Braddock Road), and have put in a traffic light at each one. Isn't that moving in the wrong direction?

In CA, many cloverleafs are being replaced with partial cloverleafs (aka parcelos). Typically, the offramp loop is removed, and the offramp becomes a single ramp with a stoplight at the arterial road. Two remaining onramp loops are retained. This arrangement eliminates the dangerous weaving and accelerating/decelerating that clog up heavily used cloverleafs.

Partial cloverleaf interchange - Wikipedia, the free encyclopedia

I agree that the recent interchange reconfigurations are a step in the right direction, but the design is still so flawed given the level of traffic in this area. It's like VADOT is applying 1970s design to 21st century problems.

P.S. I'm thrilled that my thread won the wonky award!

[Curbed Enthusiasm]

Originally Posted by tysonsengineer

The era in which most of the infrastructure was built in NOVA is really why. You are looking at design standards used in the industry between 1975 and 1995 when major highway projects were largely complete in VA. Specifically the 495 interchanges. Is your particular issue with them the fact that they are both deceleration and acceleration lanes?

Compared to the new Caltran intersections they use far less right of way, which is one reason the federal highway system utilized them in the first place. Staggered flyovers can be seen, for instance look at the newly built Route 28 limited access system, but again those take up way more right of way than equivalent cloverleafs

BTW, this is the wonkiest thread ever created on the subject of transportation. Well played

What Caltrans intersections are you comparing the cloverleaf to? I would argue that the cloverleaf requires some of the most right of way of any interchange design.

You mentioned Route 28 - compare the right of way of a cloverleaf with that of the Willard Road (Chantilly) interchange. It's a Single Point Urban Interchange (SPUI), had a very efficient traffic pattern (one intersection for all ramps at the arterial road), and takes up very little land.

[reebo]

"parcelos" - Must work that into conversation today...