To Clear or Not to Clear

The holidays is a busy travel season for many people, so this article might come a little late for the holiday-only travelers, but for the road warriors who use this season to rest before hitting the road again, I hope this is helpful. 

Last week, CNN published an article featuring complaints regarding services that are meant to help reduce waiting times at airport security: 

“TSA PreCheck members are complaining on social media of longer wait times than regular security in some cases, while Clear members are grumbling that they paid more than TSA PreCheck members for slower service. Travelers are scratching their heads over which to choose.”

The reported complaint is simple: despite being a convenient option for frequent travelers, waiting times for TSA PreCheck and Clear are becoming longer and longer. Interestingly, on some occasions it seems more efficient to opt for the regular security lines instead. As a TSA PreCheck and Clear customer, I’ve experienced this firsthand, especially at Newark Airport. The lines for TSA PreCheck and Clear have been noticeably longer over the last year. 

Long-time readers of this newsletter know that it’s impossible for me to remain silent when the words ‘complaint’ and ‘waiting lines’ are mentioned, let alone if the phrase ‘paying for priority’ is thrown into the mix. 

In today’s article I will attempt to address the question of whether travelers should choose TSA PreCheck, Clear, or neither.

The Options

The choices available to passengers before they reach the airport are: 

• TSA-PreCheck, which costs $78 for five years. 

• Clear, which costs $189 for one year. 

• Neither option. 

When a traveler reaches airport security: 

• With neither option, they must stand in the regular line. 

• With TSA- PreCheck, they can stand in the regular line or the TSA-Pre line. 

• With Clear (but not TSA- PreCheck), they can stand in the regular line or the Clear line. 

• And if they have both TSA- PreCheck and Clear, they can choose either of the following lines: regular, TSA-Pre, or Clear. 

It’s important to note that not all airports offer all options. For example, PHL doesn’t have Clear, while Newark and SFO have them all. 

Given that travelers must commit to these choices in advance, our analysis will aim to determine which option is the most beneficial. This will involve considering various costs associated with wait times and other relevant factors. But first, let’s understand what each service actually offers. 

When comparing the two, we must acknowledge that they are quite different. TSA PreCheck offers a distinct set of resources—dedicated lines for expedited service for those cleared by a security process—whereas Clear provides a shortcut through only a portion of the line, with both services sharing the same ultimate resource: the security checkpoint. 

The following diagram shows the options:

One of the key distinctions between Clear and TSA PreCheck lies in the type of priority and efficiency they offer. TSA PreCheck provides a separate line with dedicated staff, which leads to shorter waiting times. Since fewer people sign up, and there’s no need to remove shoes, the waiting time is significantly less, and the variance in wait times is lower.

Clear operates differently. It offers two scenarios: one with TSA PreCheck and one without. The first scenario involves a short verification process to confirm your identity, after which you are escorted to the front of the TSA PreCheck line. This can be highly efficient, especially if there’s ample capacity, and allows you to bypass the line with only a brief wait for identity verification.

However, when there’s a larger group of people using Clear, it leads to waiting in multiple lines: first for identity verification, then for TSA PreCheck (which is fast since you are escorted to the head of the line), and finally, for physical screening. Additionally, if capacity for identity verification is insufficient—verifications are done one at a time—this can actually make the process more cumbersome than just going through TSA PreCheck, where there’s only one additional checkpoint.

Often, the dilemma is deciding between the efficiency of the person checking identities at Clear and the speed of TSA’s dedicated PreCheck line. As more people use Clear, without sufficient capacity, waiting time becomes an increasingly significant issue. While Clear can be useful, it comes at an additional cost, which raises the question of, “Why shouldn’t someone just choose the simple TSA PreCheck instead?”

My goal is to dissect the differences between the services, analyze the wait times—even with limited data—to model this behavior, and then interpret the comparative benefits of TSA PreCheck alone versus the combination of Clear and TSA PreCheck.

Strategic Decision-Making in Queues

Conventionally, service systems advocate for the ‘avoid the crowd’ strategy, where choosing the less popular option can be beneficial. For instance, if most people choose Line A, it might be wiser to join Line B. This is obvious, so if most people don’t have TSA-PreCheck, it makes sense to get TSA-PreCheck. And even if we were to remove the additional convenience of keeping your shoes on and your laptop in, it’s clear that, for frequent travelers, TSA-PreCheck is a no-brainer (and many airline loyalty programs actually cover the fee). 

However, this decision-making becomes more nuanced if we’re talking about buying priority access. Priority queues, have the feature of ‘join the crowd.’ If many opt for priority and you don’t, your position may be negatively impacted by being deprioritized. Conversely, if no one buys access to priorities, obtaining one could prove advantageous. This is true when buying a priority pass that gives you access to the same resource (imagine Disney or the London Eye). But what if the priority queue has its own resources, which can become overwhelmed with excess demand? Buying Clear is essentially like buying priority access, only with the additional caveat that you need an additional resource to verify your identity. 

Of course, this begs the question: Why are these lines, which are designed to be faster, becoming progressively longer? 

It might be due to the imbalance between capacity usage and the demand for them.

Enrollment in TSA PreCheck has seen a significant uptick, with figures reaching over 18 million—a 30% increase from 2022. Despite TSA’s encouragement for more sign-ups to PreCheck, there’s been a slight uptick in wait times amid this surge. Currently, 92% of PreCheck passengers experience less than a five-minute wait, a slight decrease in efficiency from 99% in 2016, though the vast majority—99%—still pass in under ten minutes.

However, the growing number of PreCheck passengers is not the sole cause of slower lines. The integration of new 3-D luggage scanners, which allow travelers to leave liquids and laptops in their bags, has also contributed to increased processing times. Additionally, airlines and airports are facing staff shortages, further impacting the flow of security lines.

So it’s clear that staffing levels must be adjusted to meet demand, and currently, it seems there’s room for improvement. But assuming that additional capacity isn’t coming any time soon, let’s look at the past year and try to understand which option is better. 

Estimating Waiting Times 

The goal of this newsletter is to help readers make better decisions, but also to highlight the depth needed to make these decisions. As I mentioned, PHL doesn’t have Clear but Newark does. So let’s base our analysis on the “data” that was possible to obtain on both services as well as Nerwark-specific data. 

To analyze TSA PreCheck airport security wait times, we’ll fit a mixture of two distributions to the data. Since our approach is somewhat speculative due to the absence of raw data, we’ll base our analysis on summary statistics: the average wait time is 16 minutes, end- to-end, and 92% of passengers wait less than 5 minutes (cited in the CNN article). The only way to get to these numbers is to have multiple scenarios, each with its own distribution —one when the airport is nearly empty and passengers experience short wait times, and one when the airport is more congested and passengers must deal with longer wait times.

For those interested, I used an Expectation-Maximization (EM), an iterative algorithm to achieve the best fit for the observed data, thus maximizing the likelihood of the model.

Given that we only have summary statistics and not individual data points, our fitting process is an educated guess about the proportion of passengers in each group and the parameters of their respective gamma distributions. After optimization, we find the following parameters for our two gamma distributions:

For the group that arrives at a less congested airport (Distribution 1): Shape (k1): 2.00 and Scale (θ1): 1.00 minute.

For the group that arrives at a more congested airport (Distribution 2): Shape (k2): 8.00, and Scale (θ2): 2.00 minutes.

The proportion of times a passenger encounters a less congested airport is about 70%.

For a visual perspective, we can plot these distributions. The mixture of the two gamma distributions is shown in blue, representing the PreCheck passenger wait times. The individual gamma distributions are also shown - Distribution 1 (less congested) in a green dashed line, and Distribution 2 (more congested) in a red dashed line. A purple dashed line at 5 minutes marks the 92nd percentile, showing that most passengers wait less than this time.

This model, although not perfect, provides a nuanced view of passenger wait times, suggesting there are distinct experiences within the population. 

We can do the same now for the Clear line (from start to finish, including the physical screening), given the information that, on average, it takes 5 minutes to go through both. 

Using a similar estimation process, the new parameters we determined are:

For Gamma Distribution 1 (less congested): Shape (k1): 1.38 and Scale (θ1): 2.19 minutes

For Gamma Distribution 2 (more congested): Shape (k2): 2.39 and Scale (θ2): 2.39 minutes

The proportion of the first gamma distribution in the mixture is approximately 26.25%. 

Again, to better understand the implications of these parameters, we can visualize the new mixture of the two gamma distributions:

To analyze and compare the waiting time distributions for TSA PreCheck and Clear, we’ll visualize both distributions on the same plot. The TSA PreCheck waiting time distribution is depicted in orange, while the Clear distribution is shown in blue. The average waiting times for Clear and TSA PreCheck are highlighted with purple and green dashed lines, respectively, at 5 minutes for Clear and 16 minutes for TSA PreCheck.

From the plot, it’s evident that the TSA PreCheck distribution is broader, indicating a more diverse range of waiting times with a tendency toward longer wait times. The Clear distribution is tighter, centered around shorter wait times, suggesting that passengers usually move through it faster. 

Don’t be Mean: It’s About Variances

Let’s take a look at the implications of our analysis. 

When compared to having no priority service, a significant benefit of TSA PreCheck, despite occasional longer lines, is the reduced uncertainty in wait times compared to regular lines. Regular lines can be unpredictable, leading to potentially long waits if you choose an inopportune time. This is also true when you compare TSA PreCheck+Clear and TSA PreCheck. Clear + TSA PreCheck generally offers a more consistent experience, with multiple lines moving smoothly, resulting in reasonable waiting times.

So, focusing on the variance in wait times is crucial as people usually dislike unpredictability more than the wait itself. In systems like TSA PreCheck and Clear, reducing the variance in wait times is key to enhancing passenger experience, as it provides a sense of reliability and efficiency, even if, on occasion, the actual wait is longer.

If the variance in wait times increases, travelers who are risk-averse to missing flights (like me), must allocate a larger buffer time to ensure that they’re on time. This buffer time tends to increase significantly with the variance in wait times. 

And indeed, our analysis above shows that TSA PreCheck has a higher variance in waiting times compared to TSA PreCheck + Clear. This means that the waiting times for TSA PreCheck are more unpredictable and can vary widely when compared to Clear, which tends to have more consistent and predictable waiting times.

To Buy or Not to Buy?

To decide whether Clear + TSA PreCheck or TSA PreCheck is more cost-effective, we can conduct a cost-benefit analysis based on the value of a passenger’s time. This involves assigning a monetary value to each minute of waiting and calculating the annual cost of waiting for both services. This calculation also considers the annual membership fee for Clear, which is $189.

The results of this analysis depend on how much a passenger values their time. If the value assigned to each minute of waiting is high, Clear might be more financially beneficial despite its membership fee due to shorter waiting times. However, if the value of time is lower, TSA PreCheck could be more economical despite longer waits.

In a cost-benefit analysis for passengers who fly once a month (an assumption that can be changed), I looked at how the value of time (ranging from $0 to $100 per hour) affects the choice between TSA PreCheck and Clear. This analysis considers both the waiting time and membership costs for Clear.

The orange line indicates the annual waiting cost for TSA PreCheck. The blue line shows the total annual cost for Clear, including the membership fee. I’m assuming that the person already has TSA PreCheck and is only deciding whether or not to also puchase Clear. 

The plot suggests that for a person flying once a month, the total annual cost of Clear (including both membership and waiting time) is higher than the annual waiting cost of TSA PreCheck for almost all hourly time values up to $100.

This outcome highlights the significant impact of Clear’s fixed membership fee in the analysis, particularly for less frequent flyers. The actual cost of waiting becomes less influential due to the reduced frequency of flights. Essentially, for someone who doesn’t fly often, the high fixed cost of Clear membership might not be offset by the reduced waiting times, making TSA PreCheck a more economical choice in most scenarios.

But, if you visit the airport once a month, and you value your time more than $90 per hour, you should get Clear. If you visit the airport more often (say, once a week), it’s almost a no-brainer to get Clear. 

Other Considerations 

Other things to consider are the potential criticism on Clear for allowing customers to bypass the TSA line, considering it a violation of a basic societal norm against cutting in line. This can be particularly frustrating for travelers who have been patiently waiting their turn. But this is part of a broader debate on whether priority for a public good should even be a commodity to be bought and sold. My personal response is YES. Based on the assumption that people value time differently, passengers should be allowed to buy priority to security lines as a way to allow the system’s manager to elicit the right value of time from each passenger. In turn, the additional funds can be used to further improve the system for everyone. So in general, I would say that priority makes sense in this case, but not always. For example, I’ve written about priority queues and why I don’t think they make sense on ski slopes. 

Another point raised is that Clear is primarily a biometric-data company, which requires customers to share sensitive personal information (like iris and fingerprint scans) for convenience. This raises privacy concerns regarding how the data is managed and used. While Clear states that it doesn’t sell user data, the article highlights concerns about how the company might use the extensive data it collects, given the potential value of such information.

I think there’s also a question of whether this should be run by a public firm or the government. My experience with TSA agents is that they’re usually very good and careful in how they do their job, but also very courteous (personal experience, clearly anecdotal). I can’t say the same for all Clear agents. Most of them are ok, but I’ve been in several situations at Newark and SFO where I had to tell them how to do their job (for example that if there’s no one in the TSA PreCheck line, they can escort me there). I didn’t get the impression that the service is better because the process is carried out by a private company. 

To conclude, as someone particularly cautious about waiting too long and even more concerned about missing a flight, managing a tight schedule becomes challenging. Despite disliking the unpredictability and acknowledging the need for greater capacity at airport checkpoints, I still prefer to use services like Clear and TSA PreCheck. This preference remains even if it means occasionally having to wait in line. This approach allows me to balance my dislike for insufficient capacity with my need to manage risks associated with tight schedules and the potential of missing flights. 

So there you have it—my attempt to untangle the Gordian Knot of airport security lines. Whether you end up feeling like a VIP in the fast lane or just another traveler in the queue, remember: the only true certainty in travel is that there’s always a Starbucks on the other side (or La Colombe if you’re flying through PHL). 

Safe travels and may your coffee be strong and your wait times be short!