the “server.” A particularly slow server, like a particularly slow traffic light, bears the brunt of our frustration. As with traditional queues, traffic engineers try to estimate the flow of “arrivals.” Do cars arrive in a random way, or in a “Poisson” process (after the French mathematician Siméon-Denis Poisson), as in a bank queue? Or is it non-Poisson, nonrandom (think of immigration queues at airports, which are periodically flooded by “platoons” of deplaning passengers)? Traffic engineers extend the “cycle time” during peak hours in the same way a Starbucks might add employees during the morning rush.
There are also “moving queues,” as when you’re in the faster left-lane on a highway, stuck behind what engineers call a “platoon” of vehicles. As some vehicles shift to slower lanes, you can “move up” the queue. If someone is in your way you might flash your lights or crowd their tail, which is roughly the equivalent of lightly coughing or tapping the shoulder of someone who is daydreaming in line ahead of you and has forgotten to move. You may have noticed how we tend to do this even when it clearly will not change the overall wait time, as if the sight of empty space makes us anxious.
Traffic congestion baffles traditional queue logic. We are waiting in a queue, but we often do not know where it begins or ends. How are we to measure our progress? Whether or not traffic always acts like a traditional queue, what’s interesting is that it seems to affect us in exactly the same way. David Maister, an expert in “the psychology of queuing,” has come up with a series of propositions about waiting in line. Strikingly, they all seem to hold true for traffic.
Take proposition no. 1: “Unoccupied time feels longer than occupied time.” This is why grocery stores put magazines near the cashiers, and why we listen to radios or talk on cell phones in our cars. Or proposition no. 3: “Anxiety makes waits seem longer.” Ever been stuck in traffic on your way to an important meeting or when you were low on gas? Or proposition no. 4: “Uncertain waits are longer than known, finite waits.” This is why highway engineers use CMS, or “changeable message signs,” to tell us how long a stretch of commute will take. Studies suggest that when we know the exact time of a wait, we devote less attention to thinking about it. Traffic engineers in Delhi, India, have put up “countdown signals” on a number of traffic lights, marking the number of seconds until the light turns green, for this very reason.
Also worth considering is proposition no. 6: “Unfair waits are longer than equitable waits.” Think of ramp meters, those signals that delay drivers’ entrance onto the freeway. Drivers fume: Why should I have to wait on the ramp while the freeway is moving? One study found that people thought of waiting on the ramp as 1.6 to 1.7 times “more onerous” than waiting on the highway itself. The more people understand the purpose of ramp meters (which I will discuss in Chapter 4), the less bothersome the wait becomes. This relates to proposition no. 5: “Unexplained waits are longer than explained waits.” Hence our frustration when we find no “cause” for a traffic jam. If we know there is an accident or construction, the delay is easier to process. Proposition no. 8 is appropriate, too: “Solo waiting feels longer than group waiting.” One study found that solo drivers placed the highest value on saving time in traffic. The implication is that they are more affected by delays than people not traveling alone, which is ironic, considering that under HOV lane schemes people traveling in groups often move faster.
Queues, wherever they occur, play strange games with our perception of time, our feeling of satisfaction, even our sense of “social justice.” Studies have shown that people routinely overestimate the amount of time they have actually spent in a queue, and thus are less
There are also “moving queues,” as when you’re in the faster left-lane on a highway, stuck behind what engineers call a “platoon” of vehicles. As some vehicles shift to slower lanes, you can “move up” the queue. If someone is in your way you might flash your lights or crowd their tail, which is roughly the equivalent of lightly coughing or tapping the shoulder of someone who is daydreaming in line ahead of you and has forgotten to move. You may have noticed how we tend to do this even when it clearly will not change the overall wait time, as if the sight of empty space makes us anxious.
Traffic congestion baffles traditional queue logic. We are waiting in a queue, but we often do not know where it begins or ends. How are we to measure our progress? Whether or not traffic always acts like a traditional queue, what’s interesting is that it seems to affect us in exactly the same way. David Maister, an expert in “the psychology of queuing,” has come up with a series of propositions about waiting in line. Strikingly, they all seem to hold true for traffic.
Take proposition no. 1: “Unoccupied time feels longer than occupied time.” This is why grocery stores put magazines near the cashiers, and why we listen to radios or talk on cell phones in our cars. Or proposition no. 3: “Anxiety makes waits seem longer.” Ever been stuck in traffic on your way to an important meeting or when you were low on gas? Or proposition no. 4: “Uncertain waits are longer than known, finite waits.” This is why highway engineers use CMS, or “changeable message signs,” to tell us how long a stretch of commute will take. Studies suggest that when we know the exact time of a wait, we devote less attention to thinking about it. Traffic engineers in Delhi, India, have put up “countdown signals” on a number of traffic lights, marking the number of seconds until the light turns green, for this very reason.
Also worth considering is proposition no. 6: “Unfair waits are longer than equitable waits.” Think of ramp meters, those signals that delay drivers’ entrance onto the freeway. Drivers fume: Why should I have to wait on the ramp while the freeway is moving? One study found that people thought of waiting on the ramp as 1.6 to 1.7 times “more onerous” than waiting on the highway itself. The more people understand the purpose of ramp meters (which I will discuss in Chapter 4), the less bothersome the wait becomes. This relates to proposition no. 5: “Unexplained waits are longer than explained waits.” Hence our frustration when we find no “cause” for a traffic jam. If we know there is an accident or construction, the delay is easier to process. Proposition no. 8 is appropriate, too: “Solo waiting feels longer than group waiting.” One study found that solo drivers placed the highest value on saving time in traffic. The implication is that they are more affected by delays than people not traveling alone, which is ironic, considering that under HOV lane schemes people traveling in groups often move faster.
Queues, wherever they occur, play strange games with our perception of time, our feeling of satisfaction, even our sense of “social justice.” Studies have shown that people routinely overestimate the amount of time they have actually spent in a queue, and thus are less
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