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InTransition Magazine : Transportation Planning, Practice & Progress

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Research Exchange

About 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.

Oil Supply Disruption Deemed Top National Security Risk

The economic costs of a major disruption in global oil supplies—including higher prices for American consumers—pose a serious U.S. national security risk, according to a RAND Corporation study released in May. The study evaluated commonly suggested links between oil imports and national security. It also assessed the economic, political and military costs and benefits of potential policies to address threats to national security associated with imported oil.

According to the researchers, some of the security risks officials tend to focus on are “overblown.” For instance, the threats from oil revenues financing small terrorist groups, competition for oil supplies among other nations and the use of energy exports to influence other countries in ways detrimental to U.S. interests were deemed minimal. The threats from higher oil revenues financing “rogue” oil-exporting nations and groups like Hamas and Hezbollah were said to constitute moderate risks.

The study contends that the U.S. should pursue policies that lessen its sensitivity to a sudden decline in the oil supply, whether or not the oil is imported. By reducing demand or increasing competitive alternative energy supplies, the U.S. would place downward pressure on world oil prices and ease its security risks, according to the study.

Four energy policies were recommended to reduce the costs to U.S. national security of importing oil: Support well-functioning oil markets and refrain from imposing price controls or rationing during times of severe supply disruptions; initiate a high-level review of prohibitions on exploring and developing new oil fields in restricted areas; ensure that licensing/permitting procedures and environmental standards for developing and producing oil and oil substitutes are clear; and impose an excise tax on oil to encourage drivers and manufacturers to lower their demand for oil.

The report, “Imported Oil and U.S. National Security,” can be found at The work was sponsored by U.S. Institute for 21st Century Energy, an affiliate of the U.S. Chamber of Commerce.

—Researchers: Andreas Goldthau, Michael Toman, Thomas Light, Stuart E. Johnson, Alireza Nader, Angel Rabasa and Harun Dogo, the RAND Corporation.

Blind Struggle to Hear New Cars
in Certain Road Conditions

A recent study suggests that today’s quieter cars may have made crossing at non-signalized intersections more dangerous for blind pedestrians, particularly in certain physical environments.

In the 1940s, instructors began teaching visually impaired and blind students how to use their hearing to determine when it was safe to cross. The “cross when quiet” strategy was effective at the time, according to the study, but the loudness of cars was cut in half by 1972, a trend that will only continue with the advent of electric and hybrid vehicles.

Twenty-three participants with visual impairments and normal hearing abilities were stationed along quiet, two-way residential streets in the Silver Spring, Md., area that lacked traffic control devices. The participants were asked to raise their right or left hand when they first heard a vehicle approaching from the right or left. Sound meters and speed guns were set up at the sites. The tests took place on six sites with distinct environmental conditions: a straight road with no obstacles; straight with a noise barrier nearby; a severe bend in the road; a minor bend in the road; a hill sloping away from the participant; and an approach heavily lined with trees.

Those conditions, as well as vehicle speeds and ambient sound in the neighborhood, all appeared to impact the participants’ abilities to hear the cars. Across all the conditions, the average safety margin was 2 seconds—that is, the car arrived two seconds after a typical pedestrian would have finished crossing, assuming they started just before hearing the vehicle.

At the road with the severe bend, safety margins were 0, meaning half the
participants would not have been able to complete their crossing before the car reached them. The roads with the minor bend and hill tied for the second-worst safety margins at 3 seconds, while the straight, unobstructed road fared the best, with a 6-second safety margin. Out of the 805 total trials conducted, safety margins ranged from -5 to 28 seconds, and detection times—the span between when the participants recognized the sound to when the vehicle passed them ranged from 2 to 35 seconds.

The full study, “Detecting Approaching Vehicles at Streets with No Traffic Control,” was published in the December 2008 issue of the Journal of Visual Impairment & Blindness.

—Researchers: Robert Wall Emerson, Western Michigan University, Dona Sauerburger, orientation and mobility specialist, Gambrills, Md.

Findings Challenge Green Image
of Mass Transit Services

When it comes to measuring transportation’s carbon footprint, the tailpipe is just part of the tale. A recent study contends commonly sourced statistics comparing the benefits of mass transit to car travel are flawed because they only consider the emissions produced by operating the vehicles and overlook peripheral pollution contributions, like the fossil fuels burned to manufacture them, generate their electricity or maintain their infrastructure.

Dallas Area Rapid Transit

To help calculate the true environmental cost of travel, researchers created a framework to measure the damages caused by these less-considered factors. Consideration was given to a variety of vehicles, from hatchbacks and pick-ups to light and heavy rails, small planes and jumbo jets.

Among their conclusions, the researchers said that while Boston’s light rail is touted for its low energy use, it is actually a far larger greenhouse gas emitter than San Francisco’s light rail because 82 percent of the energy generated for Boston’s system is fossil-fuel based, compared to only 49 percent for San Francisco’s.

According to the study, the level of occupancy must be weighed when comparing the environmental friendliness of one transport mode to another. The researchers calculated that a half-full Boston light rail train is only as green, per passenger-kilometer traveled, as a midsize aircraft at 38 percent occupancy. A commuter train filled to 34 percent capacity (147 passengers) is equivalent, per passenger-kilometer traveled, to a bus with 13 passengers or a sedan with one rider, once all of the secondary sources of energy consumption tied to these vehicles are considered.

The study, “Environmental assessment of passenger transportation should include infrastructure and supply chains,” was published in the online journal Environmental Research Letters in June.

—Researchers: Mikhail Chester and Arpad Horvath, the Department of Civil and Environmental Engineering at the University of California, Berkeley.

Conventional TOD Traffic
Estimates Called Too High

Transit-oriented developments (TOD) generate only about half the auto traffic that industry standards assume, according to a study of 17 such sites throughout the U.S. The study’s authors suggest that cities and municipalities should revise their zoning standards to reflect these findings and offer greater incentives to build TODs. Burden

A pair of researchers compared the number of vehicle trips per dwelling at housing complexes near rail stations in four parts of the country—Philadelphia/New Jersey, Portland, Ore., Washington, D.C. and San Francisco— to what the widely consulted Institute of Transportation Engineers’ Trip Generation manual estimated the numbers would be. Professional engineering firms were contracted in each area to set up traffic-counting equipment and record statistics from two typical weekdays in May 2007, before the onset of the summer vacation season.

Over this period, the TODs averaged 44 percent fewer trips than what the manual predicted, or 3.754 actual trips per dwelling daily vs. 6.715 estimated. The largest difference was found in Washington, D.C., where the actual rates were 60 percent lower than the prediction. The trip statistics measured at the Philadelphia/New Jersey sites were the closest to the manual’s estimates, but were still roughly one-quarter less than predicted.

The authors said incentives such as lower off-street parking requirements, streamlined project review and permitting processes and lower traffic impact fees should be offered for TOD projects. “[S]mart growth needs smart calculus—those who build projects that lower the need to make vehicle trips should be rewarded in the form of reduced traffic impact fees and exactions. The expectation is developers would pass on some of the cost savings to tenants, thus making housing more affordable near rail stations.”

The full study, “Vehicle Trip Reduction Impacts of Transit-Oriented Housing,” was published in the Journal of Public Transportation, Vol. 11, No. 3, 2008.

—Researchers: Robert Cervero, University of California, Berkeley; G.B. Arrington, PB PlaceMaking, Portland, Ore.

Study Estimates Lives Lost
from Low Seatbelt Use Rate

A U.S. Department of Transportation study released in May estimates that 1,652 additional lives could be saved and 22,372 serious injuries avoided each year if seatbelt use rates rose to at least 90 percent in every state. The study, based on 2007 data, also reports that seatbelts saved 15,147 lives that year.

The national seatbelt use rate, estimated to have been 82 percent in 2007, is based on the National Highway Transportation Safety Traffic Safety Administration’s (NHTSA) National Occupant Protection Use Survey. The number of lives saved was calculated by taking the effectiveness of seatbelts into account. In addition, the study estimates $5.2 billion in emergency service, court, insurance and other costs could be saved annually if the rate rose above 90 percent in each state.

According to the report, 38 states and Washington, D.C., had seatbelt use rates below 90 percent. Lowest among them were New Hampshire (63.8), Massachusetts (68.7) and Arkansas (69.9). New Hampshire and Massachusetts were two of 22 states with rates below 90 percent that did not have primary seatbelt laws (which allow police to pull over motorists for the violation alone) on the books in 2007. Of the 13 states and territories above 90 percent, the highest that year were Hawaii (97.6), Washington (96.4) and Oregon (95.3). The only state or territory without a primary seatbelt law that held a use rate above 90 percent was Nevada, at 92.2 percent.

The report, “The Increase in Lives Saved, Injuries Prevented, and Cost Savings if Seat Belt Use Rose to at Least 90 Percent in All States,” can be viewed online at

—Researchers: Marc Starnes and Lawrence Blincoe, the National Center for Statistics and Analysis (NCSA), NHTSA, Washington, D.C.

Social Acceptance Influential
to Bicycle Commuters

Belgians living in bikeable areas appeared to rate personal factors—such as peer acceptance, perceived benefits and perceived barriers—over physical determinants in their choice of whether or not to ride to work, according to a recent study.

A survey of 343 residents of the Flanders region divided them into a cycling group and non-cycling group, with cyclists defined as those who rode to work within the last six months. No statistical differences were found among age or gender, although those living outside of big cities were 56 percent less likely to commute by bike. Cyclists tended to have higher education levels (67 percent) and saw the ecological and economic advantages of riding (cheaper, better for the environment, etc.) as more important than non-cyclists.

Overall, the cyclists believed they had social norms on their side—they more often rode with companions than non-cyclists, and felt like their peers provided encouragement to ride. The riders were also more likely to find support at work, where facilities like showers and bike racks were available for them. No differences were found between cyclists and non-riders regarding the influence of traffic variables (congestion, crime, the presence of bike lanes, etc.) on their decisions to ride. Perceived barriers like a lack of time (job and family commitments) and a lack of interest were rated as important reasons non-riders didn’t use bikes for transport.

The authors suggested that their findings could be used to influence more people to commute by bike. “Promotion campaigns aimed at increasing cycling for transportation should focus on creating social support by encouraging cycling with partners, increasing selfefficacy, raising ecological and economic awareness, decreasing lack of time and interest barriers and providing facilities for cyclists at the workplace.”

“Psychological and Environmental Factors Associated with Cycling for Transport Among a Working Population” was published in the August 2008 issue of Health Education Research.

—Researchers: Bas de Geus and Romain Meeusen, Vrije Universiteit Brussel (Belgium); Ilse De Bourdeaudhuij and Caroline Jannes, Ghent University (Belgium).

Researchers Deem Unusual
Bus U-Turn Design Safe

Researchers examining an unconventional bus U-turn design at a Miami intersection concluded it posed no major safety concerns, as long as the volume of traffic it handled is less than 4,000 vehicles per hour. The City of Sunny Isles Beach asked Miami-Dade Transit to evaluate the safety of buses making a U-turn at an intersection on Collins Avenue/SR A1A, a 35 mph arterial road with a median separating three northbound and three southbound lanes of traffic.

Buses approaching the intersection are confined to a dedicated lane six feet to the right of regular traffic. At the intersection, bus drivers must observe a special traffic signal that is not visible to drivers in the regular lanes. The signal gives bus drivers a window of time to make a U-turn past the northbound lanes to the left and enter the southbound lane along the curb and sidewalk. The design allows the buses to turn around and continue their routes without using a jughandle or local roads.

Traffic records from 2001 to 2003 showed five bus-related crashes occurred at the intersection. All of the crashes were reportedly caused by others driving carelessly or ignoring traffic signals, and none resulted in anything worse than property damage. In addition, eight hours of videotape were recorded with a camera mounted on top of a resort building 1,000 feet south of the intersection. The researchers studied the footage to observe any instances when drivers had to brake, swerve or take any other action to avoid a crash. There were 48 such traffic conflicts recorded, only two of which were
caused by the bus U-turns.

According to the study’s authors, the traffic signal sequence allows this U-turn to work while causing minimal confusion to drivers. “To unsuspecting motorists, there should not be any conflicting information displayed—they simply see standard traffic signal indications. When it is the bus’s turn to go, the motorists see standard traffic signal indications. When it is the bus’s turn to go, the motorists see a red signal and should be expected to abide by it.”

The full study, “An Unconventional Design for Bus U-Turns at Signalized Intersections,” was published in the Journal of Public Transportation, Vol. 11, No. 4, 2008.

—Researchers: Huaguo Zhou, Southern Illinois University; Pei-Sung Lin, University of South Florida; Joan Shen, Miami-Dade County Public Works.

Tests May Predict Driving Ability
of Alzheimer’s Patients

Doctors may be able to use off-road cognitive tests to help determine whether a person with Alzheimer’s disease has the capacity to safely get behind the wheel.

In a University of Iowa study, 40 people diagnosed in the early stages early Alzheimer’s disease and 115 healthy elderly participants underwent a battery of tests that measured thinking, movement and visual skills. The participants also drove a 35-mile route in a car outfitted with hidden recording equipment and sensors. Driving safety errors were recorded by a driving expert, based on a video review of the drive. Among drivers with Alzheimer’s disease, those who performed better on the off-road tests made fewer on-road
safety errors.

The research found drivers with Alzheimer’s disease committed an average of 42 safety mistakes, or 27 percent more than their non-impaired peers, who made an average of 33.2 safety errors on the test drive. The most common mistakes were lane violations. For every five years older the participant was, the number of safety errors increased by 2.3, whether or not they had Alzheimer’s disease.

“The goal is to prevent crashes while still maximizing patients’ rights and freedom to be mobile,” said study author Jeffrey Dawson. “By measuring driver performance through off-road tests of memory, visual and motor abilities, we may be able to develop a standardized assessment of a person’s fitness to drive.”

The full study, “Predictors of driving safety in early Alzheimer’s disease,” was published in the Feb. 10 issue of Neurology.

— Researchers: J.D. Dawson, S.W. Anderson, E. Dastrup and M. Rizzo, University of Iowa.

Refusing Police Sobriety Tests
Makes Troubles Worse

Drunk drivers who refuse to take sobriety tests may think they’re helping their case, but an analysis of court records found that those who don’t comply tend to see higher conviction rates, costlier fines and longer incarceration times.

To gauge the extent of blood-alcohol content (BAC) test refusals, National Highway Traffic Safety Administration (NHTSA) researchers examined 2005 data from 37 states, Puerto Rico and Washington, D.C. They found 22.4 percent of those arrested for driving while intoxicated (DWI) refused to take a BAC test, with a high rate of 81 percent in New Hampshire and a low of 2.4 percent in Delaware. There were 1,460,498 DWI arrests nationally
that year.

The NHTSA also examined the impact of refusals on the prosecution of DWI cases in three jurisdictions. In Ramsey County, Minn., refusers averaged 55 days in jail and $1,098 in fines, vs. 21 days and $794 for those who complied; in Bernalillo County, N.M., refusers averaged 42 days and $74, vs. 23 days and $52; and in Omaha, Neb., refusers averaged 27 days and $720, vs. 19 days and $502. The report noted that the sample was too small to draw
definitive national conclusions, but added that the two jurisdictions (Minnesota and Nebraska) that considered refusal a separate offense saw higher conviction rates for both drivers who refused and complied with the tests.

The report encourages states to enact laws that criminalize BAC test refusals, allow refusal evidence in court and impose penalties for refusal that are at least as stiff as those carried for DWI convictions. It also encourages states to review their laws and get rid of any outdated provisions that may impede the prosecution of DWI cases.

“Refusal of Intoxication Testing: A Report to Congress” was completed in September 2008, and can be viewed online at

—Researchers: A. Berning, R. Compton, M. Vegega, D. Beirness, J. Hedlund, R. Jones and J. Nichols, NHTSA Office of Behavioral Safety Research.

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