Significant Reduction In Speed Research Articles

Long-Term Effectiveness of Speed Monitoring Displays in Work Zones on Rural Interstate Highways

The long-term effectiveness of speed monitoring displays (SMDs) was evaluated as part of the Midwest States Smart Work Zone Deployment Initiative, a pooled-fund study sponsored by Iowa, Kansas, Missouri, Nebraska, and FHWA. Three SMDs were deployed for a 5-week period along a 4.35-km (2.7-mile) section between two work zones on I-80 near Lincoln, Nebraska. The mean, 85th percentile, and standard deviation of vehicle speeds and the percentage of vehicles complying with the 89-km/h (55-mph) speed limit and the 97 and 105-km/h (60 and 65-mph) speed thresholds were used as measures of effectiveness (MOEs). The SMDs were found to be effective in lowering speeds, increasing the uniformity of speeds, and increasing speed-limit compliance over the 5-week period. Statistically significant improvements in speed parameters and speed-limit compliance were observed at the measurement points downstream of the first two SMDs. The improvement in standard deviation and some compliance percentages were not statistically significant at the third SMD. Greater speed reductions and compliance increases were observed for passenger cars than for other vehicles. The combined longterm effect of the three SMDs was also assessed using spatially aggregated MOEs. Statistically significant improvement was found in terms of both speed reduction and speed-limit compliance. One week after the removal of the SMDs, there were still statistically significant speed reductions and compliance increases, although they were less than during the deployment.

Relationships Between Ball Bank Indicator Readings, Lateral Acceleration Rates, and Vehicular Body-Roll Rates

The objective of the current AASHTO criteria for horizontal curve design is to select the radius and superelevation so that the lateral acceleration perceived by the occupants of vehicles traversing horizontal curves is kept within comfortable limits. It is considered good design practice to provide roadways on which these comfortable lateral acceleration limits are not violated within an appropriate range of speed values. However, because of geometric constraints, some horizontal curves require significant speed reductions to maintain motorists’ comfort levels. The ball bank indicator has been used since the 1930s to measure the speed at which occupants become uncomfortable. Reported in degrees, the reading of the ball bank indicator is the sum of a vehicle’s lateral acceleration and the body-roll minus the roadway superelevation. Ball bank indicator readings and lateral acceleration levels are both indicators of safe speed based on vehicle occupants’ comfort levels. Both have been used for highway design since first being introduced, although they are related only theoretically. The criteria for using ball bank indicators have been modified only slightly in the last 50 years, while vehicle technology and societal changes have experienced significant changes. Ball bank indicator readings were correlated with lateral acceleration rates. Additionally, the influence of vehicular body-roll on ball bank indicator readings was investigated. Ball bank indicator readings and lateral acceleration values were found to be highly correlated. The influence of body-roll on ball bank indicator readings appears to be negligible when using typical passenger cars to determine safe speed on horizontal curves.

Costs and benefits for water strider (Aquarius paludum) females of carrying guarding, reproductive males

We describe the mating system of Aquarius paludum insularis based on field observations and test hypotheses about the effects of body size, hunger level and post‐copulatory guarding on reproductive performance. The mating sequence of this species was typical for temperate water striders, except that most oviposition was carried out by tandem pairs, most of which were submerged. Mate guarding continued until the end of oviposition, lasting up to 18.2 h, which was much longer than that recorded for other species of water striders. Pair partners changed after oviposition. Extended contact guarding reduced female mobility. In the case of females that carried long‐winged males, there was a significant reduction in speed and stride between tandem as opposed to single females. However, when short‐winged males were carried, there was not a significant difference. Short‐term foraging efficiency did not differ significantly between tandem and single females, and thus did not reflect the difference in mobility. Hunger level did not significantly affect female mating receptivity. Although the number of harassment bouts by unpaired males did not differ between single and tandem females, single females suffered significantly more harassment. Females were able to lay fertilized eggs for about 15 days after a single copulation, but they accepted long guarding and multiple mating during this period as well. The cost of resisting male mating attempts appears to be greater than the cost of carrying males.

Explosive volcanic eruptions-IX. The transition between Hawaiian-style lava fountaining and Strombolian explosive activity

The commonest eruption styles of basaltic volcanoes involve Hawaiian lava fountaining or intermittent Strombolian explosions. We investigate the ways in which magma rise speed at depth, magma volatile content and magma viscosity control which of these eruption styles takes place. We develop a model of the degree of coalescence between gas bubbles in the magma which allows us to simulate the transition between the two extreme styles of activity. We find that magma rise speed is the most important factor causing the transition, with gas content and viscosity also influencing the rise speed at which the transition occurs. Counter to intuitive expectations, a decrease in gas content does not cause a transition from Hawaiian to Strombolian activity, but instead causes a transition to passive effusion of vesicular lava. Rather, a change from Hawaiian to Strombolian style requires a significant reduction in magma rise speed.

The relationship between maximum cardiac output and swimming performance in northern squawfish, Ptychocheilus oregonensis: the effect of coronary artery ligation

The objective of this study was to determine whether experimental reductions in maximum cardiac output would reduce the swimming performance of northern squawfish, Ptychocheilus oregonensis. The reduction in maximum cardiac output was accomplished using ligation of the coronary arteries, and the effectiveness of the ligation depended upon fish size. Maximum cardiac output was significantly reduced in coronary-ligated fish greater than 320 g, but was unchanged in smaller fish. The reduction in maximum cardiac output was due to a significant decrease in maximum stroke volume, with no change in maximum heart rate. Despite the significant reduction in maximum cardiac output in the larger fish, there was no significant reduction in critical swimming speed.

The effects of continuous operation in a chemical protective ensemble on the performance of medical tasks in trauma management.

Treating casualties in a chemically hazardous environment constitutes a unique problem. Physical protection of the medical personnel may impair their performance and potentially affect patients' prognoses. The present study examined the effect of prolonged physical protection on the accomplishment of medical tasks related to trauma management. Sixty one emergency medical technicians, acclimatized to operating in protective gear, underwent four rounds of testing during eight hours of continuously wearing either a chemical protective suit or regular fatigues. The quality of the designated medical tasks, including sterility, was maintained throughout the study. A significant reduction in speed of performance was noted (approximately 30% slowing, p < 0.0001 in multivariate analysis) because of protective clothing. There was no additional decrement in performance following a prolonged stay in the protective gear. We conclude that in a chemically contaminated area, fully protected medical personnel are capable of treating trauma patients reasonably well, and for a relatively long period of time. The importance of pretraining and proper instruction is emphasized.

EFFECTS OF PUBLIC POSTING ON DRIVING SPEED IN ICELANDIC TRAFFIC

We replicated a study by Van Houten, Nau, and Marini (1980) that had revealed reductions in vehicle speeding following the posting of percentages of drivers not speeding on a sign at roadside. Our subjects were drivers entering a residential area where the speed limit changed from 90 km/hr (55.9 mph) to 60 km/hr (37.3 mph). A total of 4,409 vehicle speeds were taken from two observation sessions per day for 20 consecutive weekdays. The intervention consisted of a single posting condition, in which a hypothetical daily percentage of drivers not speeding was posted on a feedback sign, followed by a double posting condition, in which a sign posting a best result was erected beyond the feedback sign. Results revealed a significant speed reduction from an average of 69.0 km/hr (42.9 mph) during baseline to 63.4 km/hr (39.4 mph) during single posting. Average speed during double posting was 62.9 km/hr (39.1 mph). The percentage of drivers exceeding 70 km/hr (43.5 mph) dropped from 41.0 during baseline to 20.5 during single posting. The significant speed reductions add to the generality of findings of similar studies in Canada and Israel and offer possible explanations for the failure of feedback posting to reduce speed in the U.S.

Coastal-Trapped Waves in Continuously Stratified Channels. Part I: Numerical Description of Behavioral Properties

Abstract A numerical model which solves the linearized, quasi-geostrophic potential vorticity equation is used to describe free subinertial coastal-trapped wave (CTW) properties in channels with variable depth in the offshore direction, and with surface intensified buoyancy frequency profiles N2(z) as found in large and deep estuaries. The variational form of the pressure equation reveals that CTWs propagate slower in channels as compared to those on continental shelves, due to the bottom slope reversal between the channel shores. Significant phase speed reduction occurs when the effective channel stratification parameter in O(1) or higher. Without coastal walls, phase speeds of long topographic waves increase with channel width and vertical averaged N2, but decrease with channel concavity and N2 surface intensification. Bottom-trapped motion is enhanced in channels relative to that on continental shelves, again due the bottom slope reversal. In the presence of coastal walls, hybrid waves are less affecte...

A neurological study of hand function of hemiplegic children.

Twenty-five children with hemiplegic cerebral palsy between the ages of five and 15 years were examined in more detail, using a torque generator motor. A significant reduction in distal power, fatiguability and speed of movement was found on the hemiplegic side. Proximal power was relatively well preserved. Muscle tone, as would be expected, was significantly increased on the affected side and this was demonstrated by a significant rise in measured resonant frequency. Phasic spasticity in response to stretch was found on EMG to be much more common than phasic and tonic combined. Hand function correlated well with the loss of distal power and speed of movement. There was wide individual variation in the relationship between increased muscle tone and hand function. Thixotropy was normal in spastic muscles. Use of the unaffected hand had a marked effect on muscle tone and EMG of the affected side.

Migration redefined? Seasonality, movements and group composition of humpback whales Megaptera novaeangliae off the west coast of South Africa

The migration of Southern Hemisphere humpback whales Megaptera novaeangliae between their feeding and breeding areas has thus far been considered a highly predictable and seasonal event. However, previous observations on the humpbacks that pass through the nearshore waters of the west coast of South Africa have revealed deviations from the behaviour and seasonality expected during a typical migration. This ‘anomaly’ is hypothesised to be associated with prey availability in the region. Shore-based observations between July 2001 and February 2003 from North Head, Saldanha Bay, in the Western Cape province, yielded relative abundances that again did not support a classical migration pattern, with the highest sighting rates from mid-spring through summer. Movement parameters (actual swimming speed, direction and linearity) of humpback groups tracked by theodolite showed mid-spring to be a turning point in their behaviour, after which we observed a significant reduction in actual swimming speed, an increase in ‘non-directional’ movement, and a distribution farther from shore than in other seasons. Additional data on group composition and sex collected between 1993 and 2008 showed a significantly female-biased sex ratio during mid-spring, the first such recorded for any region. Direct observation of feeding on crustacean prey during spring and summer further supports the notion that humpbacks may have more flexible foraging habits than previously appreciated, and that the southern Benguela upwelling region may function as an important feeding area for these whales.