Walter Yu, P.E., LEED AP

The freeway, not the soda!

Growing up in Southern California, I grew accustomed to the sight of freeway interchanges with their flyovers arching gracefully over one another.

Even after moving to the Bay Area, I came to admire the MacArthur Maze for its (mostly) graceful combination of the I-80, I-580 and I-880 freeways through West Oakland.

So it’s a surprise to find a recent New York Times article citing them as works of art.

The article begins by discussing the Orange Crush interchange where the I-5, SR-22 and SR-57 freeways intersect.

It’s the first four-level interchange in the world and serves as a center of reference for commuters and traffic reports alike.

Aside from their size and complexity, interchanges are making a comeback as a part of shovel-ready projects being funded by the Obama Administration. The American Recovery and Reinvestment Act (ARRA, also mentioned in my post on California High Speed Rail) has committed over $20 billion to highway improvements and repairs (there are currently 5000 under construction out of a total 8000 authorized).

Many of these projects are intersection improvements, where freeways or roadways intersect. Most are much needed and would improve safety and traffic flow.

One safety improvement being made to many intersections is the circular interchange, which routes traffic in a loop around the intersection roads. I know first hand about these loops, having driving through them around the side streets of Berkeley.

In addition to discussing basic intersection design and current project funding, the article gives a brief history of intersections, which were first constructed to accommodate automobiles sharing the road in the late 1920’s. One of the first was a cloverleaf built near Woodbridge, N.J.

Intersection design varies with local conditions and culture – for example, New York famously prohibits right turns after stopping at red lights. Here in California, turning after stopping is one of the first rules taught in driving school.

States such as Michigan and New Jersey have their own designs, complete with nicknames: Michigan Left and Jersey Jughandle.

In conclusion, it’s comforting to know that much of the stimulus funding committed to roadway projects involve safety improvements, not just traffic flow. Although reducing traffic congestion is an important part of roadway design, it isn’t the top priority (safety is).