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01/11/2008 Can We Blame Highway Congestion on Cell Phones?
As if those who depend on highways for their living did not have enough reasons to dislike drivers talking on cell phones, researchers at the University of Utah have found that these drivers may be contributing to a very large problem. According to a recently completed study, drivers speaking on cell phones could very well be contributing to the traffic congestion throughout the country.
The main finding of the study- “Drivers’ Lane Changing Behavior While Conversing On a Cell Phone in a Variable Density Simulated Highway Environment”- was that drivers talking on the phone were less likely to change lanes when traffic was high or medium, which led to “significantly” higher travel times. Drivers on the phone changed lanes less, averaged a lower speed and experienced a significant increase in travel time in high- and medium-density traffic. When a vehicle spends more time behind a slow lead vehicle, it affects the speed of other vehicles behind it, adding to congestion.
The study argues that while the delays might seem trivial when looked at individually, given the extensive use of cell phones throughout the country, the cumulative effect of thousands of distracted drivers “could lead to dramatic differences in traffic flow characteristics.
“Given that 10 percent of drivers are conversing on a cell phone during a typical daylight moment, the overall impact of cell phone use on traffic flow could be substantial,” the study reports.
Study Results
With the data collected, researchers examined: lane change frequency, turn-signal count, time following a lead vehicle (the time the lead vehicle position was either less than or greater than 60 meters from the participant vehicle), driving speed, following speed (lead car is within 60 meters), speed while not within 60 meters of lead vehicle, and travel time saved.
Based on data gathered from the experiment, researchers were able to reach four main conclusions:
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Drivers on the phone changed lanes less in medium- and high-density traffic
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Drivers on the phone followed a lead vehicle longer, increasing travel time.
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Whether a driver was on the phone or not did not observably affect following distance.
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There was no noticeable effect on use of a turn signal.
Speaking on the phone while driving and traffic density “significantly impacted” lane change frequency. When drivers were speaking, they made 21 percent fewer lane changes in the medium-density condition and 19 percent fewer in the high-density condition.
Drivers who changed lanes more often finished a 9.2 mile drive up to 90 seconds faster in medium-density traffic.
Overall, drivers on the cell phone took 2.3 percent and 2.7 percent longer to complete the medium- and high-density scenarios, respectively.
While the study found that talking on the phone did not impact the vehicle’s speed or following distance, drivers conversing spent “significantly” more time behind a slower lead vehicle. “This indicates that the overall speed decrease for drivers on the cell phone was a direct result of their increased reluctance to change from the slower to the faster lanes.” Compared to drivers not conversing, drivers on the cell phone spent 31, 16, and 12 percent more time following a slower lead vehicle in the low-, medium- and high-density scenarios, respectively.
Previous research on the subject has found that 55 percent of the time, a lane change is initiated because the driver wants to pass a slower vehicle, and when this is done safely and efficiently, it will have a beneficial impact on traffic flow. This argument was supported by the study.
“Considered in isolation, these figures may not be sufficient to dramatically alter traffic flow, however, when coupled with other observed characteristics of the distracted driver such as reductions in brake reaction time, changes in acceleration/deceleration profiles, and modifications to following behavior in braking situations, the effect of distraction on traffic flow could be substantial,” the study said.
About the Study
The experiment was prompted as researchers and engineers have been looking at ways to alleviate traffic and congestion other than through highway expansion. They have determined that cell phone use could very well be contributing to congestion throughout the country. According to the study, “research suggests that many critical components involved in traffic flow, such as individual following distance, speed, and acceleration/deceleration, differ when drivers are conversing on a cell phone.”
The study was conducted by researchers at the University of Utah. It involved 36 University of Utah undergrads in a PatrolSim driving simulator.
Participants each drove six 9.2-mile scenarios. The study presented drivers with three traffic flow situations, light, medium and heavy, in order to mirror varying real-world driving situations. Drivers were allowed to freely change lanes and to drive at their own pace. The cell phone was adjusted and positioned before driving started to mirror a hands-free device.
About cell phone use
According to the Cellular Telecommunications and Internet Association (CTIA), wireless phone subscribers in the U.S. increased by 600 percent from 1995 to 2006. It is estimated that there are more than 240 million cell phone users in the country. A study performed by Nationwide Insurance found that as many as 73 percent of cell phone subscribers admit to using their phone while driving. The National Occupant Protection Use study estimated that 10 percent of drivers were using their cell phones at any time during daylight driving in 2005.
Previous studies have found that when drivers are speaking on the phone they are:
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Up to four times more likely to be involved in an accident. Researchers have determined that the risk of being in an accident while speaking on a cell phone is as high as driving while legally drunk (BAC of .08 or higher).
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Drive differently than non-distracted drivers.
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Drivers adopt increased time headways to traffic and reduce speed.
Cell Phone Laws
As a response to the increase of cell phone use, five states (California, Connecticut, New Jersey, New York and Washington) have adopted laws that require drivers to use a hands-free device. Researchers concluded that “once conversation is initiated, hands-free devices may fail to eliminate the distraction effect. Thus, the majority of current regulation appears to be misguided and is unlikely to eliminate the distraction effect.”
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