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There is currently no commonly accepted or adopted measure of pedestrian and bicycle exposure to risk. Consequently, a large portion of the field of pedestrian and bicycle safety is lacking an adequate means to evaluate the effectiveness of its efforts. The current study presents a proposed metric for measuring pedestrian and bicycle exposure to risk: hundred million pedestrian or bicycle miles of roadway (or other motor vehicle shared facility) traveled. A method for implementing the proposed exposure metric is described for eight shared-facility types characteristic of the urban environment of Washington, D.C. These facilities include three types of intersections, midblock road segments, driveways, alleys, parking lots, parking garages, school areas, and areas with playing, dashing, and working in the roadway. The methodology is then used to calculate the annual pedestrian and bicycle exposure for the city for the calendar year 2007. The results of these calculations revealed 0.82 hundred million miles for pedestrian exposure and 0.37 hundred million miles for bicyclist exposure. In this way both the feasibility and scalability of the proposed metric were successfully demonstrated for a relatively large urban environment. Thus the proposed metric has the potential to eliminate one of the major obstacles in the pedestrian and bicycle safety field, the lack of adequate exposure data. Although further refinement and validation are still needed, the proposed metric provides a possible initial foundation to develop a national unit of risk exposure for pedestrians and bicyclists.

The Segway Human Transporter is becoming more prevalent on urban sidewalks. This experiment investigated the approach speed and passing clearance that Segway devices exhibit on encountering a variety of obstacles on the sidewalk. The experiment was conducted with a sample of 20 Segway operators: 10 experienced operators and 10 novices. For the given experimental course and procedures, the results of the study revealed that ( a) Segway riders approach obstacles at a mean speed of about 4.5 mph (7.2 km/h) with a range from 2.7 mph (4.3 km/h) to 6.8 mph (10.9 km/h); ( b) Segway riders pass obstacles with a mean clearance of about 14.5 in. (36.7 cm) with a range from 3.3 in. (8.4 cm) to 43.2 in. (110 cm); ( c) Segway riders pass moving pedestrians at an average speed of about 5 mph (8.1 km/h) and with an average clearance of 35.9 in. (91.2 cm); ( d) Segway riders pass obstacles more slowly by about 0.5 mph (0.8 km/h) on average and closer by about 17.6 in. (44.7 cm) on average on a narrow as opposed to a wide sidewalk; and ( e) experienced Segway riders pass faster by about 1.9 mph (3.1 km/h) on average than do novice riders. In the current experiment, the average passing event involving a Segway rider and a pedestrian required a minimum total distance of approximately 7.0 ft (2.1 m). These data should assist engineers in calculating the impact of various mixes of Segway traffic on sidewalks.

The FHWA Turner-Fairbank Highway Research Center is undertaking a research program to study the visibility of retroreflective raised pavement markers (RRPMs). The focus of the initial effort is to determine the relative luminance of RRPMs and pavement markings (PMs) needed to produce adequate guidance on rural two-lane roadways at night. A driving simulator was used to test 36 research participants as they drove simulated roadways containing various combinations of RRPMs and PMs. The luminance of the simulated roadway delineation ranged from 0.07 to 4.1 cd/m2. The primary driver performance measure was curve-recognition distance. For the various RRPM and PM luminance conditions, mean curve-recognition distances ranged from 19.0 m (62.3 ft) to 68.4 m (224 ft), with a grand mean of 43.0 m (141 ft). Regression analyses produced predictive equations to estimate the mean curve-recognition distance from the luminance of RRPMs acting alone or of PMs acting alone. Trading ratios were computed for PM luminance with and without RRPMs present on the road. A conservative empirical estimate of 0.52 was computed for such a trading ratio based on the data from the current experiment. This value compared favorably with independent estimates of 0.54 and 0.55 based on an earlier analytical approach. Thus, the current experiment confirmed, with empirical data, earlier estimates that it might be possible to reduce the luminance of PMs on rural two-lane roads by about 45% when appropriate RRPMs are installed.

NASA is developing space telerobotic systems to construct, service and maintain complex space hardware. These systems will be controlled by an astronaut operator in space. Preliminary mission procedures have been developed and typical task elements have been selected. The present study simulates some of these procedures, tasks and devices in the laboratory in order to obtain initial operator/robot system performance data.

A series of three psychoacoustic experiments was conducted with samples of audible (corona) noise tape recorded 15 m (50 ft) from extra-high-voltage transmission lines. Altogether 77 listeners responded to these and other sounds in a realistic listening room environment. The results showed that Corona noise is more aversive than the ambient sounds (including rainfall) occuring near rural transmission lines and that knowledge of the source of the corona noise did not affect its aversiveness to the listeners. The results also showed that common acoustic measurement scales tend to underestimate the aversiveness of corona noise and that the high-frequency components of corona noise contribute most toward the aversive reactions of listeners.

A Driving Fitness Form was developed to ensure that drivers areready to participate in field driving experiments at night. The form was tested in afield experiment conducted in Delta, Pennsylvania, during August 2004. The fieldexperiment was part of a cooperative research program conducted by the FederalHighway Administration and the Pennsylvania Department of Transportation.Sixteen research participants drove a curvy stretch of rural two-lane highway eachnight for 8 nights with different pavement markings and markers on the roadway.Partly due to the Driving Fitness Form, the experiment was completedsuccessfully by all participants without any incidents or crashes. The DrivingFitness Form performed well, and summary data were collected on the sample of16 drivers.

An experiment was conducted to simulate executing a proposed on-orbit Space Station maintenance task by means of a telerobotic system. A battery Orbital Replacement Unit (ORU) changeout task was simulated in the laboratory. This task was performed by 5 experienced robot operators using full-scale mockups of the ORU battery module and its interfaces. The space telerobot was emulated by a pair of Kraft robot arms mounted on a Cimcorp gantry robot. The results of the experiment demonstrated that the preliminary flight procedures defining the ORU changeout task worked well. The results also showed that the basic hardware design for the battery ORU could be manipulated by the telerobot. The effects of operator training were significant. Average task completion times improved almost 40 percent over 8 trials. The effects of training were not as pronounced on measures of performance quality, either in terms of errors made or forces and torques exerted on the ORU. Certain operator interface improvements were suggested.

This report presents the results of the third in a proposed sequence of studies to investigate human annoyance to noise from low-altitude military training route (MTR) flight operations. The sequence ranges from laboratory studies, in which the physical and social parameters are well controlled, but highly artificial, to field attitudinal surveys, in which these parameter are largely uncontrolled, but the setting is natural. In this third study, subjects were exposed to both real and recorded MTR noise events in their own homes for a period of four weeks. In the laboratory study it was found that MTR sounds having onset rates faster than 30 dB/second caused annoyance beyond what would be expected from the corresponding sound exposure level (SEL). The best fit to the data was found to be an onset rate adjustment to SEL, which has the form of a linear relation on a dB versus log (rate) scale, from 0 dB at a rate of 30 dB/second to 11 dB at 150 dB/second. The rented home study confirmed the laboratory onset rate adjustment, although the adjustment was found to begin at 15 dB/second rather than at 30 dB/second. The present study continued to confirm the existence of an onset rate effect. it also confirmed the equal energy principle. However, it did not show any dependence of annoyance on the sporadicity of the events.

Noise from military aircraft operating at high speeds and low altitude can exhibit high onset rates, which are thought to increase the annoyance of these sounds. A set of listening experiments was undertaken to examine this effect and to evaluate the validity of an onset rate adjustment currently used in the environmental assessment of this type of noise. A basic set of 12 stereo sound recordings was prepared, consisting of four types of military aircraft with various onset rates plus one civil aircraft. These aircraft flyby sounds were presented at four sound levels to subjects in an indoor listening facility (nominal SEL of 95, 85, 75, and 65 dB) and at an outdoor facility (nominal SEL of 115, 105, 95, and 85 dB). Indoor sounds were filtered according to a typical residential noise reduction curve. Sounds were presented in random order, at random time intervals, and random approach from either in front of or behind the subjects. Subjects rated each sound on a seven‐point annoyance scale. Two companion experiments were also performed at the outdoor facility. These experiments used modified military aircraft sounds with particular onset rates from 5 to 100 dB/s and decay rates from 2 to 30 dB/s. Analysis of the results of these experiments examined the effects of onset and decay rates, level, SEL, and duration. [Work sponsored by USAF AAMRL/BBE.]

A behavioral preference procedure, the ’’acoustic menu,’’ was used to assess human aversion to the sounds from two samples of transmission line audible noise and from samples of other environmental noises. The audible (corona) noise produced by extra‐high voltage (EHV), overhead transmission lines was tape‐recorded during moist weather. Reproduced samples of corona noise, other common environmental noises, and artificial reference stimuli were compared in two experiments. The two corona noise samples were found to be equally preferred to: (1) a 1000 Hz octave band of noise about 11 dB SPL higher than the corona noises and (2) a collection of other environmental noises about 8 dB SPL higher than the corona noises. The corona noise samples were more aversive than the ambient sounds (including rainfall) occurring near rural transmission lines and were roughly equivalent in aversiveness to the noise from a room air conditioner (indoor recording). Knowledge of the source of the corona noise (from photographs and a brief description) did not affect its aversiveness. Of the simple frequency‐weighting scales, the A‐weighted sound level reduced the difference between the two corona noise samples and the set of other environmental sounds from about 8 dB SPL to about 3 dB. The D‐weighted sound level further reduced this discrepancy to about 2 dB. These results were obtained with only two samples of corona noise; other samples may give different results.

The aversiveness of audible noise from EHV electric transmission lines was evaluated for spectral modifications of 5 different tape-recorded samples. The relative contributions of low-frequency humming and buzzing and of high-frequency hissing and crackling components of the noise were determined. The high-frequency components of the hoise proved more aversive for all five samples to a group of 25 listeners. Therefore, for outdoor or open window listening, engineering efforts should be directed at reducing the high-frequency portion of the audible noise spectrum.

College students tapped rapidly on a telegraph key to reduce the intensity of a continuous acoustic stimulus presented through earphones. Failure to respond resulted in an intensity increase of 1 dB every 4 sec. A group of 14 students responded during 10‐min sessions to eight pure tones and eight 1/3‐octave bands of noise at octave frequencies from 63 Hz to 8 kHz. The average SPL maintained by the subjects became stable after about 5 min. The different asymptotic levels observed from 5–10 min were taken as a measure of equal aversion levels for the stimuli. Equal aversion levels were compared with other subjective weighting contours: equal loudness level, A‐weighted sound level, perceived noise level, etc. They were closest to an A‐weighted sound level of 80–85 dB.

Ten college students gave preference judgments for 4 pure tones (120, 300, 500, and 835 IIz) and 11 tone composites constructed from combinations of the pure tones. Equal aversion (tolerance) levels were also measured for the four pure tones and for five of the composites. Sensation-level measures were employed to express aversion thresholds in order to take account of the differential sensitivity of the human ear at different frequencies. Certain operational conclusions were suggested for the design of acoustic navigation aids. The higher frequency pure tones and composites were generally more preferred, and were also tolerated at higher sensation levels. The 120-IIz pure tone was a highly non-preferred signal. The presence of a 120-Hz component in any composite lowered both the preference value and the maintained sensation level. In the case of the moderately preferred 500-Hz pure tone, adding other more-preferred, pure-tone components increased the preference for the signal.

High school students tapped rapidly on a telegraph key to reduce the intensity of a continuous acoustic stimulus presented through earphones. Failure to respond resulted in an intensity increase of 1 dB every 4 sec. In Experiment 1, a group of 19 students responded to three pure tones (125, 1,000, and 8,000 Hz) and a white noise. The different asymptotic levels observed after 4 min were taken as a measure of equal aversion levels for the stimuli. In Experiment 2, the effect of the starting intensity level (45, 70, and 90 dB SPL) was determined for a 1,000-Hz tone. Differences in the asymptotic intensity levels observed after 6 rain were not significant. In Experiment 3, no significant effect was found upon varying the number of responses required to produce a 1-dB intensity decrement in a 1,000-Hz tone. Together, the experiments demonstrated the feasibility of determining equal-aversion levels for sounds.

Six Ss made judgments of equal loudness by adjusting the intensity of comparison tones of 10 different frequencies. The comparison tones were presented diotically alternately with standaxd tones. Each standard tone remained fixed at one frequency (125, 1,000, or 8,000 Hz) and one intensity (10, 20, 40, or 70 dB sensation level)while collecting the data for any single equal-loudness contour. In this manner, families of equal-loudness contours were generated for each of the three standard frequencies. The contours for the 1,000-Hz standard were compared with those in the literature. The families of contours for the 125- and 8,000-Hz standards, determined by the same algorithm, differed in the spacing of the contours from the 1,000-Hz standard family as well as from each other. Implications for the reflexive, symmetric, and transitive properties of the equal-loudness relation axe discussed.

A modification is proposed in Hirsch's equation for determining the range of a sound source of unknown strength [H. R. Hirsch, J. Acoust. Soc. Am. 43, 373–374 (1968)]. The modified formula applies to the case where the direction of the sound source is known. Greene's comments on Hirsch's letter are investigated for their ability to predict the limitations on the resolution obtainable in human auditory ranging [D. C. Greene, J. Acoust. Soc. Am. 44, 634 (1968)]. In a brief experiment, two subjects were unable to make distance judgments for sustained pure‐tone sources over ranges of 3 to 48 ft.

Subjects made forced choices to either side of a reference direction (0°, 30°, 60°, and 75°) to locate the image of pure tones presented through earphones. Various combinations of interaural intensity differences (IID's) and interaural time differences (ITD's) were used, including some combinations which do not occur in nature. Psychometric functions confirmed the expected apparent azimuth of ITD/IID combinations based on free‐field diffraction theory and microphone measurements. The relative dominance of the intensive and temporal cues was examined at each frequency (500, 1000, and 8000 Hz). The shape of the psychometric plane for the bidimensional matrix at the 1000‐Hz 30° condition showed possible nonlinearities in the trading relation. Data were also collected from the same subjects using the same signals presented by means of distant loudspeakers in an open field. When the free‐field data were compared with the data from earphone‐simulated sounds, they showed similar angular acuities, being approxima...

A project is underway to investigate human response to transmission line audible noise. This project is developing a psychoacoustic data-base to determine the extent to which present measurement scales and human response criteria are appropriate for evaluating the environmental impact of transmission line audible noise, and to suggest different scales and criteria if necessary. A realistic listening room was used for psychoacoustic experiments in which a listener was given choices between various acoustic environments, including corona sounds, while reading a book. In another experiment groups of participants rated various sounds for their annoyance level while watching television programs. Results indicate that despite its relatively low sound level, corona noise is equally aversive to certain other environmental sounds that are 8 dB higher in sound pressure level. All of the common frequency weighting scales underestimate the aversiveness of corona noise relative to other environmental sounds. From a limited sample of comparison sounds, corona noise was found to be roughly equal in aversiveness to the noise from a room air conditioner. Knowledge of the source of the noise did not affect the relative aversiveness of corona noise as presented in the laboratory. The high-frequency hissing and crackling components of corona noise aremore » more aversive than the low-frequency humming and buzzing components. There are distinctly different kinds of corona noise which differ both in frequency spectrum and relative aversiveness. Thus, in order to assess environmental impact, long-term sampling of corona noise from different lines may be needed. Similar results were obtained from experiments involving reading and television viewing as participant activities, indicating consistent and generalizable findings. (JGB)« less

Military air tactics rely on increasing use of high‐speed low‐altitude penetration techniques. Training for this type of operation can take place in specially designated low‐altitude military operation areas (MOAs) or along military training routes (MTRs). Environmental assessment of noise from these operations has become an important factor in the design of these special use airspaces. The noise environment is different from commonly studied situations such as airport or highway noise in urban/suburban areas, and it is not obvious that the usual Ldn analysis is appropriate. Individual events are loud (maximum levels in the 100–115 dBA range) and short (10 dB down durations of a few seconds). Noise events are infrequent (typically less than 3 or 4 per day on busy routes) and occur at random times. These operations also take place in quiet rural areas. A discussion is presented of the nature of these operations and the resultant noise environment. This noise is contrasted with well‐understood noise environ...

The aversiveness of audible (corona) noise produced by extra‐high voltage (EHV) overhead transmission lines during moist weather was assessed. Samples of corona noise from two lines, other common environmental noises, and artifical reference stimuli were compared using a behavioral preference procedure. Corona noise samples were found to be equally preferred to (1) a 1000‐Hz octave band of white noise approximately 12 dB SPL higher than the corona noises and (2) a collection of other environmental noises approximately 9 dB SPL higher than the corona noises. Corona noise was significantly less preferred than the ambient noises occurring near the transmission lines. One sample of corona noise was comparable in aversiveness to a sample of room air conditioner noise; the other sample of corona noise was somewhat more aversive. While all of the commonly used frequency weighting scales correlated strongly with preference, D‐weighted sound level provided the highest correlation with the preference data and the smallest standard error bands. [Sponsored by the Department of Energy.]

Subjects (14 high‐school students) made judgments of equal loudness by adjusting the intensity of comparison tones of ten different frequencies. The comparison tones were presented diotically alternately with standard tones (1‐sec duration each). Each standard tone remained fixed at one frequency (125, 1000, or 8000 Hz) and one intensity (10, 20, 40, or 70 dB sensation level) while the data were collected for any single equal loudness contour. In this manner, families of equal loudness contours were generated for each of the three standard frequencies. The contours at 1000 Hz were compared with those for 1000 Hz in the literature. The contours for 125 and 8000 Hz, determined by otherwise using the same algorithm, were different in shape from the 1000‐Hz set as well as from each other. These differences implied a violation of the transitivity assumption in the loudness calculating algorithm. Tests for transitivity among the three standard frequencies failed in many cases.