A large road expansion project is taking place near our house and this has led to multiple busy intersections having lane closures where two lanes merge into one. As often happens, drivers in these situations often get amazingly territorial, deliberately moving over to block the closing lane hundreds of feet even before the lane is closed.

Here is the problem with this behavior: these protectors of the lanes are actually making the whole process more inefficient. Traffic moves like waves. Not everyone starts driving at once when they can so changes filter down through a line of cars. Therefore, making one single long line takes a lot longer to get through than having two lines half the size that merge at the end. We could all get to our destinations quicker if people could stop worrying that someone is getting ahead of them. People successfully merge from two lanes into one on highway ramps all the time so why can’t they don’t it construction situations?

A note: having two lanes that are supposed to merge into one is a lot different situation than one described in the Chicago Tribune yesterday. At the infamous and congested Circle Interchange, there are more dangerous situations where people try to cut into two dedicated lanes meant for another highway (say going east on the Eisenhower Expressway and getting off to exit for both the Kennedy and Dan Ryan) from a third lane that is headed in a different direction. As the article suggests, these late attempts at cutting in can be quite dangerous.

If you want to read more about this, I highly recommend Tom Vanderbilt’s book Traffic.