BUFFALO, N.Y. -- Long lines of passengers have an effect on the
speed with which airport security screeners do certain aspects of
their jobs, according to a study by researchers in the School of
Engineering and Applied Sciences at the University at Buffalo.
The study's findings demonstrate empirically for the first time
that security screeners do speed up when lines are long, but only
when inspecting laptop computers.
While the effect of long lines seems to be small, the
researchers say, the fact that it exists at all has potential
relevance for queues in all kinds of other settings, too, from
supermarket cashiers to tollbooths and border crossings.
The UB study found that the security screeners did not change
their behavior regardless of how long the lines were when
inspecting carry-on bags or plastic bins for overcoats, keys and
UB researchers made more than 40 separate trips to a mid-sized
airport, studying the correlations between how long lines were and
how long servers took to inspect each type of item.
The research was presented earlier this month at the 51st annual
meeting of the Human Factors and Ergonomics Society in Baltimore.
It also is in press with OR Insight journal.
"If you're going to have a speed-up anywhere, it's probably
safest to have it with laptops because that's a more difficult item
to hide something in," said Rajan Batta, Ph.D., professor of the
Department of Industrial and Systems Engineering and a co-author on
"We didn't see a speedup with carry-on bags when the lines were
long, so that's reassuring," he said.
The researchers, an interdisciplinary group of industrial
engineers, were interested in finding out if there is a
"speed-accuracy tradeoff" in security screening when lines are
"We conjecture that the screeners are more comfortable speeding
up inspections of laptops because that's an item they're
well-trained to inspect and because laptops are more uniform, as
opposed to carry-on bags, where there are many more variations,"
The UB researchers say that the study has implications for a
subfield of industrial engineering called queuing theory, which,
until now, has not looked specifically at how servers may change
their behavior when lines of customers get very long.
"In more than four decades of mathematical and modeling research
on queuing, there has been a general assumption that service time
is a random function with known properties and that no matter how
long the queue is, service time doesn't change," said Colin G.
Drury, Ph.D., SUNY Distinguished Professor emeritus in the UB
Department of Industrial and Systems Engineering.
Drury, an expert on the speed-accuracy tradeoff, has focused his
career on human factors, such as ergonomics, fatigue and training,
especially in the aviation industry.
Historically, segments of the service industry have developed
policies about how long their customers can be made to wait in
lines based on data that come primarily from mathematical
The UB study is one of the first to examine the question in a
"These findings will be reassuring to the Transportation
Security Administration, because the speedup we detected will not
have a drastic effect on security," said Drury.
But, the UB researchers say, the findings have implications that
go far beyond the security screening queues at airports.
"We think this study will open up a new set of theories on
queuing, because if service time does change with queue length,
then we're going to have to rewrite the models," said Drury.
He said that in some situations where it is critical that
servers not speed up when lines are long, it may be desirable to
hide or conceal the length of the line from servers, while in other
situations companies may want servers to be able to be fully
cognizant of the length of queues.
Comprised of experts in operations research, model simulations
and human factors, the UB research team takes a far more
comprehensive look at queuing than have previous studies.
In related work, the UB researchers have been able to predict
the amount of time passengers will typically spend waiting in
airline security queues.
In addition to Drury and Batta, the research was co-authored by
Li Lin, Ph.D., professor, and Clara V. Marin, doctoral candidate,
both in the UB Department of Industrial and Systems
The research was funded by the National Science Foundation.
The University at Buffalo is a premier research-intensive public
university, the largest and most comprehensive campus in the State
University of New York. UB's more than 28,000 students pursue their
academic interests through more than 300 undergraduate, graduate
and professional degree programs. Founded in 1846, the University
at Buffalo is a member of the Association of American