I-635 LBJ Express Lanes, Dallas, TX
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The point of priced express lanes can be easily summarized:  to work, they need people to explicitly not want to use them.  By design, they are not for everyone at all times of day — that’s what general purpose lanes are for.  Instead, they are for individuals who are willing to trade one kind of pain for another.

In congested freeway segments, we as travelers experience two kinds of pain:

  1. Travel Time Delay.  This is the actual amount of time that we spend waiting in traffic rather than going full-speed.  Let’s say your 15 mile trip usually takes 20 minutes, but congestion makes it 40 minutes, you have spent 20 minutes of travel time delay.
  2. Travel Time Reliability.  It’s one thing to know that your congested trip will always be 20 minutes more.  But, that’s not the case.  On congested facilities, your actual travel time may vary widely.  For example, I entered into Google Maps going from LAX to Downtown Los Angeles.  Leaving at 8:00 am on any given workday, Google tells me my trip may be between 30 minutes to 1 hour and 15 minutes.  Even if the trip is only 45 minutes (hence, 15 minutes of travel time delay), I’ll need to plan on it taking over an hour, giving me additional time penalty for the lack of reliability.

When Express Lanes are offered, they are actively managed by the transportation operator to maintain 45 miles per hour or better.  There are many ways to actively manage a facility, including restrictions on use (e.g., you must be in a carpool), flow control (e.g., traffic signals that temper the flow of vehicles into a facility), and price (e.g., using a variable toll rate that changes based upon level of demand).  This is the “tradeoff” pain.  You get to save not only the actual travel time delay but also the reliability penalty — but you must experience another pain, such as picking up a carpool partner or paying the variable fee.  Attempts to lessen this tradeoff — such as placing caps on fees or reducing the carpool requirement — can have a negative effect on the lanes’ ability to maintain 45 mph or better, and thus, eliminate the benefits of the lanes themselves.

This brings us to a recent article in the Dallas Morning News.  This article highlights that not everyone will see the value in paying to use new express lanes on I-635.  I say that’s perfectly OK, and should be embraced.  Management of the express lanes depends upon people not using the lanes as much as people using them — at any given time of any given day.  It’s the power of individual choice that allows us to make independent decisions as to whether it’s worth it to me to trade one type of pain (payment of toll, acquiring a carpool) for another (travel time delay, travel time reliability). Without the presence of the express lanes, I wouldn’t have this choice — I would only be forced to experience pain.

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