Browsing by Author "Bloomfield, John"

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The Effect of Centerline Treatments on Driving Performance
(2002-03-01) Harder, Kathleen A.; Carmody, John C.; Bloomfield, John
In pursuit of unimpeded high peak traffic flow, the Design Guidelines for Super Two Highways (Ekern, 1998) suggested several treatments for the right side of roadway. But the left side is where drivers experience great speed-differentials between their own vehicles and oncoming traffic. Harder, Carmody, and Bloomfield examined centerline treatments and possible recommendations for Super Two guidelines. The current US standard (12-foot lane / 4-inch dashes) was compared with combinations of wider lanes, wider dashes, and buffer areas. With each of the centerline treatments examined, participants kept the left side of the vehicle in the approximate center of the lane. All treatments resulted in shifting the center of the lane farther from the centerline than it was in the standard condition. Two conditions appear to be most effective in keeping drivers away from the centerline: 1) 14-foot lanes with both longitudinal rumble strips and 4-inch wide dashes marking the centerline, and 2) 12-foot lanes with 4-foot buffer marked by 4-inch wide dashes. However, implementing any of the centerline treatments should result in vehicles driving farther from the centerline, thus making it less likely that drivers will meet an oncoming vehicle. Data was gathered in a driving simulator. Further testing should be conducted in real driving situations.
The Effect of Sleep Deprivation on Driving Performance
(University of Minnesota Center for Transportation Studies, 2009-01) Bloomfield, John; Harder, Kathleen A.; Chihak, Benjamin J.
Each of twenty commercial motor vehicle (CMV) drivers participated in a single twenty-hour experimental session, during which they were continuously kept awake, but were allowed to ingest caffeine and use tobacco as they would in real-world conditions. Each participant drove in a fixed-base advanced driving simulator for approximately one hour on four occasions (at 9:00 am, 3:00 pm, 9:00 pm, and 3:00 am). The 59.5-mile (95.8-km) test route was designed with overpasses and intersections and changes in speed limits—to make the driving experience more like real-word driving. After the fourth drive, the participants were driven to the University of Minnesota’s General Clinical Research Center, where they slept for eight hours. The main result was that the steering performance of CMV drivers was impaired when they stayed awake for an extended period: There was a considerable increase in steering instability between the morning drive, at 9:00 am, and the nighttime drive, at 3:00 pm—an increase likely to have been produced by sleep deprivation. [Other results were: (1) stopping behavior improved throughout the session—suggesting practice effects; (2) after the fourth drive, there was less reduction in the participants’ pupil size—but, since there was no difference in pupil size before the fourth drive, there was no evidence to suggest that pupil size reductions could be used to predict sleep deprivation; (3) data from other visual performance tests showed no effect of time of day; and, (4) results obtained from reaction time tests did not show decrements in performance—instead there may have been practice effects.]
The Effectiveness and Safety of Traffic and Non-Traffic Related Messages Presented on Changeable Message Signs (CMS)
(2003-06-01) Harder, Kathleen A; Bloomfield, John; Chihak, Benjamin J
The objectives of this study investigating Changeable Message Signs (CMS) were to determine whether or not CMS messages really work, whether or not they cause traffic slow downs, and whether or not they have an impact on traffic flow. The participants were 120 licensed drivers from three age groups-18-24, 32-47, and 55-65 years old. Two experiments were conducted in a fully-interactive, PC-based STISIM driving simulator. Experiment One investigated the effectiveness of the following message, CRASH/AT WYOMING AVE/USE THOMPSON EXIT. In Experiment Two, the final CMS message was: AMBER ALERT/RED FORD TRUCK/MN LIC# SLM 509. Results. In Experiment Two, only 8.3% of the participants had Excellent AMBER Recall Scores, while 51.7% had Good scores. Gender significantly affected the AMBER Recall Scores-there were more females than males in the Excellent Category. A greater proportion of those who knew what AMBER Alert meant were in the Excellent and Good Categories. 21.7% of the participants slowed down by at least 2 mph. Whether or not traffic delays will result from drivers slowing to read AMBER Alerts in real life will depend on the extent of the slow downs and on current traffic density. In Experiment One, 55.8% of the participants took the Thompson Exit after seeing the Thompson Exit Message. Of the 53 participants who did not take the exit (1) 35.9% ignored the CMS message because they did not think that it applied to them; (2) 35.9% did not understand the CMS message; and (3) 22.5% did not notice the message. (It is not known why 5.7% of the 53 did not take the exit.) Changes to the wording of the messages are recommended.
The Effectiveness of Auditory Side- and Forward-Collision Avoidance Warnings on Snow Covered Roads in Conditions of Poor Visibility
(2003-06-01) Harder, Kathleen A; Bloomfield, John; Chihak, Benjamin J
Because the snowplow operator's tasks are predominately visual, warnings presented visually may interfere with critical tasks. Auditory warnings could reduce visual load if they are meaningful, effectively signal danger, and are not annoying. We conducted a driving simulation experiment-using a 210-degree forward field-of-view driving simulator-and a field test to investigate using auditory icons as side- and forward-collision avoidance warnings. Participants in the experiment drove on simulated snow-covered roads in 105-meter (344-feet) visibility conditions. Analysis of data from 28 participants showed the side-collision avoidance warnings were equally effective; lane change response times were approximately 1.1 seconds for both a single- 187/ double-beep car horn warning-although participants said the double-beep warning sounded more urgent. Analysis of the forward-collision avoidance warning data, obtained from 32 participants, showed the mean response time with a warning consisting of two bursts of screeching-tire sounds was significantly faster than with a singlescreech warning-with both warnings significantly faster than the mean time obtained when no warning was given. The poorest collision outcomes occurred with no warning-outcomes were better with the single-screech warning, and better still with the double-screech warning (which the participants said sounded more urgent than the single-beep warning). In the field test, six of seven snowplow operators preferred the double-beep side-collision warning. We recommend an auditory icon sounding like the double-beep of a car horn be used as a side-collision avoidance warning and an auditory icon sounding like two successive bursts of screeching tires should be used as a forward-collision avoidance warning. A driving simulation experiment was conducted to investigate auditory icons as side- and forward-collision avoidance warnings. The auditory warnings produced significantly faster mean response times than with no warning, and participants preferred a double-beep side collision warning over a single-beep warning. Researchers recommend a double-beep auditory warning similar to the double-beep of a car horn for side-collision avoidance and a forward-collision avoidance warning similar to two successive bursts of screeching tires.
The Effects of In-Lane Rumble Strips on the Stopping Behavior of Attentive Drivers
(2001-10-01) Harder, Kathleen A; Bloomfield, John; Chihak, Benjamin J
This project involved investigating the effect, if any, of rumble strips on stopping behavior at simulated rural-controlled intersections. Researchers used the wrap-around driver simulator at the University of Minnesota's Human Factors Research Laboratory for the project. Researchers varied the rumble strip type and the number of rumble strips and tested them on two different types of controlled intersections, two-way or four-way, and in the presence and absence of traffic. Results indicate that none of these manipulations seem to affect the point at which drivers stop at the controlled intersections or the point at which drivers start to slow down at controlled intersections. The research did reveal drivers brake more, earlier, when rumble strips are installed than they do if there are no rumble strips. Although they started to slow down at the same time and finished braking at the same time, there was more use of the brake earlier in the slowing down maneuver in the presence of rumble strips. Results also reveal that drivers brake more and earlier with full coverage rumble strips than they do with wheel track rumble strips.
The Effects of In-Lane Rumble Strips on the Stopping Behavior of Sleep-Deprived Drivers
(2005-03-01) Harder, Kathleen A; Bloomfield, John
The authors have designed three studies to investigate the influence of in-lane (transverse) rumble strips on the braking patterns of drivers when the rumble strips are used to warn drivers of an upcoming traffic control device. Prior to these studies, no empirical work existed that could provide accurate confirmation of the effects of rumble strips on braking patterns. Despite their extensive use, in-lane rumble strips are not listed in the Manual of Uniform Traffic Control Devices as an approved traffic control device.
This portion of the research involves the use of a simulator to study braking patterns among sleep-deprived drivers who encounter rumble strips upon approaching a stop sign. The 20 subjects were commercial drivers between the ages of 25 and 60 with at least three year's driving experience. Each participant drove the 60-mile test route four times. Driving performance was measured using a battery of tests, including an EyeCheck device, an acuity test, a contrast sensitivity test, a psycho-motor vigilance test and a code substitution test.
Results indicate that there was little difference in mean approach speeds to controlled intersections with or without rumble strips. However, the presence of rumble strips caused drivers to brake to a greater extent earlier in the approach. Although sleep deprivation affected the steering patterns of drivers, it did not seem to affect their braking patterns.
Evaluation Report Volume 1: System Performance and Human Factors
(2003-11-01) Harder, Kathleen A; Bloomfield, John; Chihak, Benjamin J; Shankwitz, Craig; Donath, Max
This report documents the evaluation efforts undertaken by the Minnesota Team to complement the work undertaken by the independent government evaluator, Battelle. The Minnesota evaluation team focused on two specific areas: human factors and benefit cost analyses. Human factors issues include driver acceptance, reduction in driver fatigue, the effectiveness of the driver interface, and the measurable changes in driver performance. The Driver Assistive System (DAS), which is under evaluation for the US DOT Specialty Vehicle Generation Zero Field Operational Test, is designed to provide drivers a means to maintain desired lane position and avoid collisions with obstacles during periods of very low visibility. Specialty vehicles often must operate under inclement weather conditions and associated low visibility situations. The DAS improves safety for the specialty vehicle operator by providing the necessary cues for lane keeping and collision avoidance normally unavailable during poor visibility conditions. The DAS may also improve safety conditions for the general public by facilitating all-weather emergency services, and in the case of snowplows, opening roads and keeping them passable in heavy weather for other emergency vehicles and the general motoring public.
Ramp Meter Delays, Freeway Congestion, and Driver Acceptance
(2005-05-01) Levinson, David M; Harder, Kathleen A; Bloomfield, John; Winiarcyzk, Kasia
In the current study, we conducted several experiments using both the CASP and VESP methodologies. Nominally, the same combinations of ramp meter waiting time and freeway travel time were tested in the first two parts of the CASP experiment (CASP-a and CASP-b) and in the first two VESP experiments (VESP Experiment #1 and VESP Experiment #2). The combinations of time spent waiting at ramp meters and driving on the freeway that were presented in CASP-a were the same as the combinations of desired ramp meter waiting and driving times for VESP Experiment #1. Similarly, the combinations of times presented in CASP-b were the same as the combined desired times for VESP Experiment #2. However, it should be noted that there was some variation in the actual driving times from the desired times in the VESP experiments. This variation occurred because in the VESP experiments the driving time was manipulated by varying the congestion level of the traffic in which the participants drove.
Reducing Crashes at Controlled Rural Intersections
(2003-07-01) Harder, Kathleen A; Bloomfield, John
Right-angle crashes are a problem at rural Thru-STOP intersections-accounting for 71% of the fatal crashes in Minnesota in 1998, 1999, and the first half of 2000. Using a driving simulator, we investigated the effect of several interventions intended to increase the saliency of a problem intersection in Goodhue, Minnesota. One group of 24 participants drove with the intersection modeled as it is now, while a second group of 25 drove with the interventions implemented at the intersection. On the minor road, the effect of the interventions was to make the participants to begin to reduce speed further from the intersection. On the major road, their effect was to make participants reduce speed substantially on approaching the intersection. The implications of these findings are: (i) by beginning to slow down further from the intersection, drivers will stop in a more controlled fashion and be less likely to inadvertently run the stop sign, (ii) by making the intersection more noticeable drivers should have a better view of the major road and be better able to judge whether or not it is safe to turn into the space in front of an approaching vehicle on the cross road, and (iii) if a vehicle pulled into the intersection from the minor road, necessitating an emergency braking maneuver by the vehicle on the major road, the speed reductions would produce even greater reductions in the stopping distances. Right-angle crashes would be less likely to occur, and if they could not be avoided, their severity would be reduced.
Route Preferences and the Value of Travel-Time Information for Motorists Driving Real-World Routes
(2005-05-01) Harder, Kathleen A; Bloomfield, John; Levinson, David M; Zhang, Lei
While there is a sizable body of literature on the benefits of travel information, most of it is based on theory or on simulations. This experiment analyzes results based on a field test of 117 drivers completing the same point-to-point trip in their own vehicles via five different routes. Participants traveled both arterial and freeway routes, assessed the travel information that was provided, evaluated the importance of the accuracy of the information and charted their route preferences for various trip purposes. Researchers were not looking merely for perceived time savings but driver perception of the value of the time saved in order to make projections about whether drivers would be willing to pay for accurate travel updates as a means of reducing overall cost, anxiety and uncertainty while driving. Knowledge of how much users want to pay for Advance Travel Information System (ATIS) services is necessary for the design of sustainable for-profit private services or private/public partnerships.
Waiting Tolerance: Ramp Delay vs. Freeway Congestion
(Elsevier, 2006) Levinson, David M; Harder, Kathleen; Bloomfield, John; Carlson, Kathy
Waiting tolerance at ramp meters and travel time on the freeway were measured using a computer administered stated preference (CASP) survey and a virtual experience stated preference (VESP) method employing a driving simulator.The selections varied in the number of minutes waiting at a ramp meter with vehicle speed once on the freeway. The subjects ranked the selections in order of preference. The results were statistically analyzed using a binary logit model controlling for demographics, socioeconomic characteristics, daily travel time, and personality scores.The results by the CASP method displayed a preference for freeway congestion to ramp delay, but opposite results were obtained by the VESP method. A number of reasons are posited to explain the difference, but the results indicate that method of stated preference data collection can significantly affect conclusions drawn.
Weighting Waiting: Evaluating the Perception of In-Vehicle Travel Time Under Moving and Stopped Conditions
(Transportation Research Board, 2004) Levinson, David M; Harder, Kathleen; Bloomfield, John; Winiarczyk, Kasia
This paper describes experiments comparing traditional computer administered stated preference with virtual experience stated preference to ascertain how people value stopped delay compared with stop-and- go or freeflow traffic. The virtual experience stated preference experiments were conducted using a wrap around driving simulator. The two methods produced two different results, with the traditional computer assisted stated preference suggesting that ramp delay is 1.6 – 1.7 times more onerous than freeway time, while the driving simulator based virtual experience stated preference suggested that freeway delay is more onerous than ramp delay. Several reasons are hypothesized to explain the differences, including recency, simultaneous versus sequential comparison, awareness of public opinion, the intensity of the stop-and-go traffic, and the fact that driving in the real-world is a goal directed activity. However without further research, which, if any, of these will eventually prove to be the reason is unclear. What is clear is that a comparison of the computer administered stated preference with virtual experience stated preference produces different results, even though both procedures strive to find the same answers in nominally identical sets of conditions. Because people experience the world subjectively, and make decisions based on those subjective experiences, future research should be aimed at better understanding the differences between these subjective methodologies.

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