Nighttime Operations Research Articles

Survey of Snowplow Operators About Forward Lighting and Visibility During Nighttime Operations

Snowplow operators are a valuable source of information about improving forward visibility at night in snow, fog, or rain. These men and women have a heightened awareness of forward lighting and associated visibility issues and will try various techniques to improve their ability to see. Consequently, these operators have first-hand empirical knowledge about the factors that affect forward visibility. The purpose of this study was to survey a large number of active snowplow operators to determine what issues they believed were most important for forward visibility in perturbed atmospheric conditions at night. A survey was distributed to 300 New York State Department of Transportation snowplow operators throughout New York. Respondents reported that the most effective solution was to place lamps with narrow-beam distributions, what they generally term “spot lamps,” away from the driver’s line of sight. They also reveal some apparently sound, practical observations that also should be considered for improving visibility, especially windscreen and wiper-blade designs. Of special interest too, some believe that the spectral composition of the forward lighting system should be considered. These observations led the authors to speculate on the reasons why operators were so supportive of yellow or amber lights. The results presented here are largely consistent with a similar survey performed by the Minnesota Department of Transportation.

Driver Age as a Factor in Comprehension of Left-Turn Signals

An experiment to measure driver comprehension of left-turn signal and sign configurations was conducted as part of a study to investigate the performance of left-turn signals used in various signal strategies. The responses of 191 individuals to 81 stimuli simulating left-turn signal phases were analyzed for the effect of signal message on driver comprehension. Stimuli included 17 left-turn signal displays used for permitted, protected, and protected/permitted left-turn strategies as well as left turns during nighttime or emergency flashing signal operations. Comprehension in the original study was based on a correct versus incorrect dichotomy: if the subject’s response agreed with a predetermined subset of possible answers, the answer was correct; all other answers were considered incorrect. These data are reanalyzed with three principal variations: ( a) individuals’ answers are based on a three-level correctness concept whereby answers considered incorrect in the previous study were further categorized into minor errors and serious errors depending on whether subjects incorrectly chose to “give away” their right-of-way or to violate other drivers’ right-of-way, respectively; ( b) signal message is introduced in the analysis as an explanatory variable of driver comprehension; and ( c) emphasis is placed on older drivers. Youngest, oldest, and female subjects were found to drive fewer kilometers per year than middle-aged males. Comprehension was found to deteriorate with driver age in terms of both higher serious error rates and lower correct answer rates. Flashing signals were the least well understood, whereas change and red interval stimuli were understood best by all age groups.

Aircraft noise problems and solutions at Logan International Airport

Aircraft from Logan International Airport cause noise in the surrounding communities from overflights (arrivals and departures), take-offs, landings, run-ups, and taxiing. Some surrounding communities are as close as 900 ft from the centerline of an active runway. Methods of minimizing noise impact from aircraft in the communities include: preferential nighttime runways, standard instrument departures which maximize open spaces, restrictions on types of nighttime operations, restrictions on locations and times of ground noise generation, and enforcement of these restrictions. In addition, the airport monitors the noise in the communities (continuously and by request), receives and replies to complaints, and has a soundproofing program for eligible residents. The airport has just started monitoring flight deviations from standard departure procedures. Examples will be drawn from these topics.

Photometric Requirements for Arrow Panel Visibility

Laboratory and field studies were conducted using older drivers to identify the minimum lamp intensity needed for legibility of arrows and chevrons on Type C arrow panels (APs). A field study was also conducted to determine the maximum intensity required to control disability and discomfort glare at night. Ninety-fifth-percentile data were used to represent worst-case conditions. These data were combined with the results of an analytic study to identify the angularity required for the APs to perform in all geometric situations that conform to accepted standards. The results of the research provide a specification for AP lamps that will result in the proper identification of the AP message by drivers of all ages under most conditions, at distances of up to 467 m (1,500 ft) or greater at all angles that may be anticipated, and at distances of more than 1/2 mi on-axis. Further, the specification developed sets of minimum and maximum intensity levels for nighttime operations.

Photometric Requirements for Arrow Panel Visibility

Laboratory and field studies were conducted using older drivers to identify the minimum lamp intensity needed for legibility of arrows and chevrons on Type C arrow panels (APs). A field study was also conducted to determine the maximum intensity required to control disability and discomfort glare at night. Ninety-fifth-percentile data were used to represent worst-case conditions. These data were combined with the results of an analytic study to identify the angularity required for the APs to perform in all geometric situations that conform to accepted standards. The results of the research provide a specification for AP lamps that will result in the proper identification of the AP message by drivers of all ages under most conditions, at distances of up to 467 m (1,500 ft) or greater at all angles that may be anticipated, and at distances of more than ½ mi on-axis. Further, the specification developed sets of minimum and maximum intensity levels for nighttime operations.

Omega – An Industrial Resource

This paper was originally presented at a meeting of the International Omega Association in October 1987. It describes the operational use of the Omega system for daytime air-pollution monitoring and control, and for night-time low-level pest-spraying operations in South Africa.

Time-of-day corrections in measures of aircraft noise exposure.

Results of a socio-acoustic study of human reaction to aircraft noise around Australian airports are described. The relative importance of night, evening, and daytime operations in determining overall reaction is assessed using a correlation analysis procedure. The results indicate that night-time weightings used in most existing noise exposure indices including NEF and DNL, are too large. However, other evidence suggests that both night and evening weightings should be greater than 0 dB. The optimal weightings found were about 3 dB for night-time operations and 9 dB for evening operations. However, other considerations indicate that in a practical noise index it may be more reasonable to apply a weighting of about 6 dB during both night and evening hours.

Oslo rail tunnel turns to freezing to save historic buildings : Josang, T Tunn Tunnlg, V13, N5, June 1981, P26–28

The article discusses construction problems encountered in the driving of a 3.6 km long railway tunnel beneath the city of Oslo. Varying ground conditions, historical buildings and heavy traffic were some of the problems confronting the contractors. Ground freezing techniques were used at one section where a rock depression was encountered making blasting impossible. To establish the frozen zone, locations for pipes carrying the freezing liquid were drilled from an existing tunnel during night time operations. Details of freezing equipment and techniques used are given. After freezing, tunnel blasting operations were carried out and cast-in-situ concrete lining placed. The concrete lining was increased in thickness to avoid problems of cracking near to the frozen rock face.

Performance of the NASA Laser Ranging System in Satellite Tracking

Studies to determine the ranging accuracy of the laser systems at NASA Goddard Space Flight Center have employed both long-arc orbital comparison, using optical and Doppler observations of Geos-I, and predicted trajectory comparison. The long-arc technique compares the ranges measured by the laser with those predicted by a reference orbit computed without using laser data. The second method, utilizing computed trajectory comparisons, adds laser measurements to an orbital solution to demonstrate the improvement from these data in predicting the position of a spacecraft. The pulsed-laser systems have a range accuracy of approximately 2 m, and the range noise is generally less than 1.5 m when measuring at near-earth satellite distances (1000-3500 km). Early results from laser ranging in daylight show range measurements with no appreciable increase in noise over nighttime operations.