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InTransition Magazine : Transportation Planning, Practice & Progress

Archive Edition

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Research Exchange

Research Exchange gathers brief summaries of ongoing or recently completed research about critical topics in transportation. We invite readers to suggest studies that merit inclusion by emailing intransitionmag@njtpa.org.

 

Worldwide Shipping Traffic Increases Four Fold in 20 Years

Ship traffic on the world’s oceans has increased four-fold over the past twenty years according to a paper published in the journal Geophysical Research Letters last November. Given that ship traffic is the major driver of anthropogenic ecological change in the open ocean, the study’s author, Jean Tournadre, a geophysicist from the French Institute for the Exploitation of the Sea, believes that this growth could have a lasting impact on the environment.

Using altimeter readings from seven satellite missions, Tournadre analyzed 300,000 data points collected between 1992 and 2002, generating vessel density maps to gauge trends. The largest increases in ship traffic occurred in the Indian Ocean and Chinese shipping lanes, jumping 300 percent and 200 percent, respectively, over the dataset’s 20-year span.

Every ocean experienced a boost in vessel traffic, apart from the waters surrounding Somalia, where commercial shipping has ground to a halt due to piracy activity beginning in 2006. Between 1992 and 2002, worldwide ship traffic increased a total of 60 percent, at an average rate of 6 percent growth per year. After 2002, this rate accelerated, peaking at 10 percent per year in 2011. The paper notes that the uptick in traffic is likely due to both an increase in international trade, and the expansion of merchant fleets.

Given the significant shipping growth rates established by the altimeter data, the paper raises concerns about pressures placed on the open ocean ecosystem. An atmospheric study conducted between 1997 and 2010 demonstrated that increased ship traffic is directly associated with a rise in pollutants: levels of nitrogen oxides above the Sri Lanka-Sumatra-China shipping lane increased 50 percent during those 13 years. Tournadre is hopeful that the vessel density data generated in this study could help scientists investigate ways to mitigate pollution resulting from continued traffic growth.

The paper, “Anthropogenic Pressure on the Open Ocean: The Growth of Ship Traffic Revealed by Altimeter Data Analysis,” was published in the November 2014 issue of Geophysical Research Letters.

 - Researcher: J. Tournadre, Spatial Oceanography Laboratory, French Institute for the Explotation of the Sea, Plouzané, France.

Car Commutes

Longer Car Commutes Reduce Wellbeing 

A Canadian study published last April in the journal World Leisure found that longer commutes by car reduce self-assessed wellbeing.  

Researchers from the University of Waterloo analyzed daily diaries kept by 3,409 men and women, cataloging the amount of time they spent working, commuting, or taking part in social and physical leisure activities. Participants were then asked to evaluate two factors that contribute to overall wellbeing: life satisfaction, and time pressure experienced on a day-to-day basis. Respondents with longer commutes felt increased time pressure, and reported lower levels of life satisfaction.  

Although commuting is sometimes viewed as beneficial by allowing for mental "transition time" between personal life and work, this study builds upon previous research linking car commutes to negative physical and mental effects, including increased stress, poor sleep quality, and higher rates of obesity.   

Notably, the study found an association between longer commutes and reduced physical activity. The researchers posit that this could amplify the negative effects of commuting, as physical activity is a known stress reducer. Additionally, the paper notes that certain demographic characteristics were associated with longer commutes: men, residents of urban areas, and workers with higher levels of education and household income all spent more time in the car.

The researchers believe that these findings could encourage employers to make changes that would benefit their employees and increase wellbeing – employees who are more satisfied are generally more productive. The paper suggests employers could achieve this by allowing flexible work hours or by providing either programs or facilities for employees to participate in physical fitness.

The study, "Highway to Health? Commute Time and Well-Being Among Canadian Adults," can be found at www.tandfonline.com.  

 - Researchers: Margo Hilbrecht, Canadian Index of Wellbeing, University of Waterloo, Canada; Bryan Smale and Steven E. Mock, Department of Recreation and Leisure Studies, Waterloo University, Canada.   

 

New Method Uses Taxi GPS Data to Assess Resiliency

Researchers from the University of Illinois’ College of Engineering have developed a computational method of assessing the resiliency of a city’s transportation infrastructure using GPS data recorded by taxis. The study focused on Superstorm Sandy’s effects in New York, given the wealth of data available from the city’s robust taxi network.

Typically, traffic patterns are monitored with expensive equipment which can be logistically difficult to install. The study’s authors propose that instead, taxis can serve as “pervasive, city-scale resilience sensors,” since they are constantly tracking location and trip duration data. The researchers filed a Freedom of Information Act request to obtain four years of records, which provided a dataset containing 700 million individual taxi trips.

Sandy, which hit the east coast in October 2012, was a major event that affected transportation infrastructure for nearly a week, providing the perfect opportunity to test this methodology. After creating a baseline pace for typical travel times between different regions of the city, the researchers were able to determine when traffic deviated from that pace due to extreme events. Since each period of traffic disruption is described with a meaningful set of statistics – how many minutes were added to a trip per mile – this methodology allows for quantitative comparison between types of events to determine what a city can endure, and where improvements should be made.

At its worst, Sandy added two minutes of travel time to each mile driven by taxis. Surprisingly though, the study notes that while the evacuation process only caused minor disruptions, significant delays were encountered during the reentry process, suggesting that traffic management may need to focus more heavily on recovery.

The researchers hope that the valuable insights provided by this method of analysis will be applied in other areas of the country, helping to build more resilient infrastructure through real-time transportation monitoring.

The study, “Using Coarse GPS Data to Quantify City-Scale Transportation System Resilience to Extreme Events,” is available on University of Illinois’ Civil and Engineering Department website.

 - Researchers: Dan Work and Brian Donovan, Department of Civil and Environmental Engineering, University of Illinois College of Engineering.

 

Prevalence of self-reported drowsy driving in the United States

More than two in five drivers have admitted to falling asleep or nodding off while driving at some point in their lives, yet nearly all drivers – 97 percent – say it is unacceptable for a person to drive when they are so tired it is hard to keep their eyes open.

With car crashes among the leading causes of death in the United States, the AAA Foundation for Traffic Safety conducted a study aimed at updating data on drowsy driving. The research found that nearly a third of all drivers reported operating a vehicle in the 30 days prior to taking the survey while they were so tired they could barely keep their eyes open.

Of the 31.5 percent who admitted to driving while drowsy in the last 30 days, 3.5 percent said they did so fairly regularly, according to the study released in November 2015.

This behavior was most prevalent among drivers ages 19 to 24, of which 39.6 percent admitted to driving while drowsy, 3.1 percent of which said they did so regularly. They were closely followed by drivers ages 25 to 39, 34.7 percent of whom said they had driven while tired in the last 30 days. This group had the highest number of respondents – 5.3 percent – admitted to regularly driving while tired.

The study found that the nation’s youngest drivers, those ages 16 to 18, were the least likely to drive when tired, with only 16.3 percent saying they had done so at least once in the last 30 days.

Not surprisingly, the rate of drowsy driving is tied to the amount of sleep a driver receives. Drivers who reported sleeping less than 6 hours per day at least once a week in a typical one-week period were more like to have reported that they fell asleep while driving in the past year than those who slept at least 6 hours a night consistently.

The AAA Foundation also analyzes data from a sampling of crashes that were the subject of in-depth investigations to develop a model to estimate what percentage of those drivers were drowsy while operating a vehicle. A foundation analysis of data from 1999 to 2008 estimated that drivers were drowsy in 7 percent of all crashes in which a vehicle was towed, 13 percent of crashes that resulted in a hospital admission and 17 percent of fatal crashes during that time period.

Using the updated study data, AAA estimates that from 2009 to 2013, drivers were drowsy in 6 percent of all crashes in which a passenger vehicle was towed, 13 percent of crashes that resulted in a hospital admission and 21 percent of fatal crashes.

The AAA Foundation collected this data as part of its 2015 Traffic Safety Culture Index, a survey of U.S. residents ages 16 and older, which was conducted in English and Spanish from July 20 to August 12, 2015. The study is based on data collected from 2,545 participants who reported they were licensed drivers and had driven at least once within 30 days before completing the survey.

The AAA Foundation Study, “Prevalence of Self-Reported Drowsy Driving in the United States,” can be viewed on the foundation’s website.

Researchers: Lindsay S. Arnold & Brian C. Teft, AAA Foundation for Traffic Safety

 

Pedestrians and Cyclists: Cities, States and DOT Are Implementing Actions to Improve Safety

States across America have implemented safety programs, but a growing number of pedestrians and cyclists are being killed or injured in traffic incidents, according to a study released by the U.S. Government Accountability Office (GAO) in December.

From 2004 to 2013, overall traffic fatalities in the United States decreased by more than 10,000 people or about 24 percent, from 42,836 in 2004 to 32,719 in 2013. But the change in pedestrian and cyclist deaths and injuries has not been as dramatic. In 2004 there were 4,675 pedestrian fatalities and that number has ranged from 4,109 to 4,892 annually since. Meanwhile, the rate of pedestrian injuries has dropped only slightly from an estimated 68,000 in 2004 to an estimated 66,000 in 2013.

Similarly, there were 727 cyclist deaths in 2004 and that number has ranged from 623 to 786 annually since then. The estimated number of cyclist injuries was 41,000 in 2004 and that has increased to an estimated 48,000 in 2013.

Pedestrian fatalities comprised 14.5 percent of all traffic deaths in 2013, up from 10.9 percent in 2004, the study found. Similarly, cyclists represented 2.3 percent of all traffic deaths in the country in 2013, up from 1.7 percent in 2004.

The agency noted that walking and biking are becoming increasingly popular. The study aimed to identify challenges in addressing pedestrian and cyclist fatalities and injuries.

GAO interviewed Department of Transportation officials in three states – California, Florida and New York – and in six cities – Austin, Texas; Jacksonville, Fla.; Minneapolis, Minn.; New York City; Portland, Ore.; and San Francisco, Calif. The researchers also interviewed transportation officials from Washington, D.C., and 22 non-governmental organizations with an interest in pedestrian and cycling safety, which were selected to reflect a range of expertise. 

The states and cities were selected based on the number of fatalities, walking and cycling activities and recommendations from non-governmental organizations.

The researchers found that while a number of states and cities are implementing safety efforts, they continue to face challenges addressing pedestrian and cyclist safety. Some of the challenges transportations officials said they face are differing state and city perspectives on transportation investment prioritization; funding; incomplete data; and engineering.

For decades, the goal of street design was to move vehicles as quickly as possible. But while widening lanes and minimizing sharp curves may make it safer – and more expeditious – for vehicles to travel roadways, GAO found that many of these road improvements have contributed to the decrease in pedestrian and cyclist safety. For example, wider, straighter roads can encourage drivers to exceed posted speed limits. Crashes involving vehicles and pedestrians or cyclists are higher speeds are more likely to be fatal or cause serious injury.

GAO found that states have been more focused on moving people across longer distances and less likely to prioritize bicycle and pedestrian safety projects, however Vision Zero campaigns, which aim to implement initiatives to achieve no  pedestrian and cyclist fatalities, in places like New York City offer a more comprehensive approach to addressing the problem.

And transportation agencies are starting to implement safety features including dedicated bicycle lanes and road diets, which reduce the width and number of lanes in an effort to combat speeding.

The U.S. Department of Transportation oversaw $676 million for 13 funding programs that promote cyclist and pedestrian safety in 2013, but GAO noted that if more people chose to live and work in urban settings, there will be a need for additional programming.

The full report is available on the U.S. Government Accountability Office’s website.

Researcher: Susan Flemings, director of physical infrastructure issues, U.S. Government Accountability Office
Contributors: Sara Vermillion, Assistant Director; Carl Barden, Leia Dickerson, Georgette Hagans, Terence Lam, Leslie Locke, Joshua Ormond, Daniel Paepke, Cheryl Peterson, Michelle Weathers, Elizabeth Wood, and Friendly Vang-Johnson.

 

Modeling the Safety Impacts of Off-Hour Delivery Programs in Urban Areas

Trucks navigating city streets to make deliveries during business hours contribute to traffic congestion due to the volume of vehicles and lack of parking, which can lead to double-parking. One proposal to cut down on day-time truck traffic in urban area has been to shift deliveries to off-hours – between 7 p.m. and 6 a.m. But this shift raises concerns about safety. Although there are far fewer vehicles travelling at night, more than 50 percent of fatal crashes occur during those hours, according to the U.S. Department of Transportation.

Finding that there were few truck traffic safety studies focused on urban roadways – and those that do exist don’t distinguish between daytime and nighttime deliveries – a team of researchers at New York University’s Center for Urban Science and Progress and Rensselaer Polytechnic Institute used Manhattan, a densely populated city with a high demand for truck deliveries, as a model to study whether shifting truck delivers to off-hours would lead to safety problems.

The study used truck crash data in Manhattan from May 1, 2008 through April 30, 2011. The data was split into daytime crashes – 6 a.m. to 7 p.m. – and nighttime crashes – 7 p.m. to 6 a.m. During that time period there were 1,745 crashes, 1,404 of which happened during the day and 341 at night. Each crash was then labeled minor (property damage only, possible injury and non-incapacitating injury) and serious (incapacitating injury and fatal).

The data shows that there was a slightly higher rate of serious crashes during nighttime hours.

The researchers also collected traffic characteristics and geometric design features for all 256 road segments in Manhattan to calculate the annual average daily traffic for each roadway. This information, along with the crash data was used to develop a model to study whether increasing truck traffic at night would create safety problems in Manhattan.

The results found that for each 1 percent increase in truck volume, there would be a predicted 0.235 percent increase in daytime minor crashes and a 0.273 percent increase in daytime serious truck crashes. There’s a slightly higher, but not significant, increase during nighttime hours, a 0.238 percent increase for minor crashes and a 0.281 percent for major truck crashes.

Under a scenario where 10 percent of the truck traffic shifted to nighttime deliveries, the daytime minor and serious truck crashes were expected to decrease by 2.43 percent and 2.73 percent, respectively. At the same time, with more trucks on the road at night, minor truck crashes during off-hours increase 0.28 percent and serious truck crashes increase 1.01 percent. When increasing the number of trucks shifting from daytime to nighttime hours, the researchers found similar results – that off-hour delivery programs are not expected to significantly increase the overall risk of truck-involved crashes.

The study was partially funded by the U.S. Department of Transportation though the “Integrative Freight Demand Management in New York City Metropolitan Area” project.

New York University has made the study available online.

Researchers: Kum Xie, Kaan Ozbay, Hong Yang, Ender Faruk Morgul Center for Urban Science and Progress, New York University; José Holguín-Veras, Department of Civil and Environmental Engineering, Rensselaer Polytechnic Institute.

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