scholarly journals Classical and quantum speed limits

Quantum ◽  
2021 ◽  
Vol 5 ◽  
pp. 482
Author(s):  
Katarzyna Bolonek-Lasoń ◽  
Joanna Gonera ◽  
Piotr Kosiński
Keyword(s):  
Quantum State ◽  
Classical Limit ◽  
Speed Limit ◽  
Speed Limits ◽  
Initial Space ◽  
Relative Purity ◽  
Quantum Counterpart

The new bound on quantum speed limit (in terms of relative purity) is derived by applying the original Mandelstam-Tamm one to the evolution in the space of Hilbert-Schmidt operators acting in the initial space of states. It is shown that it provides the quantum counterpart of the classical speed limit derived in Phys. Rev. Lett. 120 (2018), 070402 and the ℏ→0 limit of the former yields the latter. The existence of classical limit is related to the degree of mixing of the quantum state.

scholarly journals Evaluating the Impacts of Speed Limit Increases on Rural Two-Lane Highways Using Quantile Regression

2021 ◽  
pp. 036119812110197
Author(s):  
Md Shakir Mahmud ◽  
Nischal Gupta ◽  
Babak Safaei ◽  
Hisham Jashami ◽  
Timothy J. Gates ◽  
...  
Keyword(s):  
Quantile Regression ◽  
Spillover Effects ◽  
Speed Limit ◽  
Passenger Cars ◽  
Cross Sectional ◽  
Speed Limits ◽  
Site Specific ◽  
Rural Highways ◽  
Speed Selection ◽  
Numerous Site

Understanding speed selection behavior of drivers following speed limit increases is critically important. To date, the literature has largely focused on freeways and the effects of speed limit changes on two-lane highways remains under researched. Prior research has generally focused on changes to mean speeds, although the speeds of both the highest and lowest drivers are also of great interest. This study investigates trends in free-flow travel speeds following 2017 legislation that increased the posted speed limit from 55 to 65 mph on 943 mi of rural highways in Michigan. Speed data were collected for over 46,000 drivers at 67 increase segments where speed limit increased and 28 control segments where speed limits remained unchanged, before and during each of the two successive years following the speed limit increases. Site-specific traffic, geometric, and cross-sectional information was also collected. Impacts of the speed limit increases on the 15th, 50th, and 85th percentile speeds were evaluated using quantile regression. Separate analyses were conducted for passenger cars and heavy vehicles. Locations where the speed limits were raised experienced increases in travel speeds ranging from 2.8 to 4.8 mph. The control sites experienced marginal changes in speeds, which suggests that any spillover effects of the higher speed limits have been limited. Significant differences were observed across the quantiles with respect to the effects of the speed limit increases, as well as numerous site-specific variables of interest. The results provide important insights about the nature of driver speed selection and the impacts of speed limit increases.

scholarly journals European birds adjust their flight initiation distance to road speed limits

2013 ◽  
Vol 9 (5) ◽  
pp. 20130417 ◽  
Author(s):  
Pierre Legagneux ◽  
Simon Ducatez
Keyword(s):  
Habitat Structure ◽  
Territory Size ◽  
Speed Limit ◽  
Vehicle Speed ◽  
Flight Initiation Distance ◽  
Speed Limits ◽  
Behavioural Responses ◽  
Road Speed ◽  
Flight Initiation ◽  
Local Speed

Behavioural responses can help species persist in habitats modified by humans. Roads and traffic greatly affect animals' mortality not only through habitat structure modifications but also through direct mortality owing to collisions. Although species are known to differ in their sensitivity to the risk of collision, whether individuals can change their behaviour in response to this is still unknown. Here, we tested whether common European birds changed their flight initiation distances (FIDs) in response to vehicles according to road speed limit (a known factor affecting killing rates on roads) and vehicle speed. We found that FID increased with speed limit, although vehicle speed had no effect. This suggests that birds adjust their flight distance to speed limit, which may reduce collision risks and decrease mortality maximizing the time allocated to foraging behaviours. Mobility and territory size are likely to affect an individuals' ability to respond adaptively to local speed limits.

scholarly journals Do speed cameras reduce speeding in urban areas?

2015 ◽  
Vol 31 (suppl 1) ◽  
pp. 208-218
Author(s):  
Daniele Falci de Oliveira ◽  
Amélia Augusta de Lima Friche ◽  
Dário Alves da Silva Costa ◽  
Sueli Aparecida Mingoti ◽  
Waleska Teixeira Caiaffa
Keyword(s):  
Observational Study ◽  
Urban Areas ◽  
Associated Factors ◽  
Cell Phones ◽  
Speed Limit ◽  
Structural Interventions ◽  
Speed Limits

Abstract This observational study aimed to estimate the prevalence of speeding on urban roadways and to analyze associated factors. The sample consisted of 8,565 vehicles circulating in areas with and without fixed speed cameras in operation. We found that 40% of vehicles 200 meters after the fixed cameras and 33.6% of vehicles observed on roadways without speed cameras were moving over the speed limit (p < 0.001). Motorcycles showed the highest recorded speed (126km/h). Most drivers were men (87.6%), 3.3% of all drivers were using their cell phones, and 74.6% of drivers (not counting motorcyclists) were wearing their seatbelts. On roadway stretches without fixed speed cameras, more women drivers were talking on their cell phones and wearing seatbelts when compared to men (p < 0.05 for both comparisons), independently of speed limits. The results suggest that compliance with speed limits requires more than structural interventions.

Emissions Impact of Eliminating National Speed Limits: One Year Later

1997 ◽  
Vol 1587 (1) ◽  
pp. 113-120
Author(s):  
Maureen A. Mullen ◽  
James H. Wilson ◽  
Laura Gottsman ◽  
Robert B. Noland ◽  
William L. Schroeer
Keyword(s):  
Maximum Speed ◽  
Speed Limit ◽  
Oxides Of Nitrogen ◽  
Speed Limits ◽  
The Past ◽  
Volatile Organic ◽  
National Highway ◽  
One Year ◽  
The Impact ◽  
Highway System

The National Highway System (NHS) bill passed by Congress in November 1995 eliminated the national maximum speed limit. It has allowed states to set their own speed limits, which many have changed during the past year. This analysis examines the impact of speed limit changes 1 year after passage of the NHS. Oxides of nitrogen (NOx), carbon monoxide, and volatile organic compounds are analyzed and are found to have increased nationwide by up to 6, 7, and 2 percent, respectively. Much of the increase has occurred in western states, which generally have increased vehicle speeds more than in eastern and midwestern states. For example, in Texas NOx emissions are estimated to have increased by 35 percent due to large increases in highway and arterial speed limits.

Lowering the speed limit from 30 mph to 25 mph in Boston: effects on vehicle speeds

2019 ◽  
Vol 26 (2) ◽  
pp. 99-102 ◽  
Author(s):  
Wen Hu ◽  
Jessica B Cicchino
Keyword(s):  
Rhode Island ◽  
Local Communities ◽  
Speed Limit ◽  
Speed Limits ◽  
State Laws ◽  
Logistic Regression Models ◽  
Road Users ◽  
Before And After ◽  
Flow Speeds ◽  
Log Linear

IntroductionEffective 9 January 2017, the default speed limit on Boston streets was reduced from 30 mph to 25 mph. This study evaluated the effects of the speed limit reduction on speeds in Boston.MethodVehicle speeds were collected at sites in Boston where the speed limit was lowered, and at control sites in Providence, Rhode Island, where the speed limit remained unchanged, before and after the speed limit change in Boston. A log-linear regression model estimated the change in vehicle speeds associated with the speed limit reduction. Separate logistic regression models estimated changes in the odds of vehicles exceeding 25 mph, 30 mph and 35 mph associated with the lower speed limit.ResultsThe speed limit reduction was associated with a 0.3 % reduction in mean speeds (p=0.065), and reductions of 2.9%, 8.5% and 29.3 % in the odds of vehicles exceeding 25 mph, 30 mph and 35 mph, respectively. All these reductions were statistically significant.ConclusionsLocal communities should consider lowering speed limits to reduce speeds and improve safety for all road users. The current practice of setting speed limits according to the 85th percentile free-flow speeds, without consideration of other characteristics of the roadway, can be a hurdle for local communities looking to lower speed limits. Updated state laws that allow municipalities to set lower speed limits on urban streets without requiring costly engineering studies can provide flexibility to municipalities to set speed limits that are safe for all road users.

scholarly journals The Geometry of Speed Limiting Resources in Physical Models of Computation

2017 ◽  
Vol 28 (04) ◽  
pp. 321-333 ◽  
Author(s):  
Benjamin Russell ◽  
Susan Stepney
Keyword(s):  
Limited Resource ◽  
Minimum Time ◽  
Physical Models ◽  
Maximum Speed ◽  
Speed Limit ◽  
Physical Computation ◽  
Speed Limits ◽  
Models Of Computation ◽  
Special Cases ◽  
Time Optimal

We study the maximum speed of quantum computation and how it is affected by limitations on physical resources. We show how the resulting concepts generalize to a broader class of physical models of computation within dynamical systems and introduce a specific algebraic structure representing these speed limits. We derive a family of quantum speed limit results in resource-constrained quantum systems with pure states and a finite dimensional state space, by using a geometric method based on right invariant action functionals on [Formula: see text]. We show that when the action functional is bi-invariant, the minimum time for implementing any quantum gate using a potentially time-dependent Hamiltonian is equal to the minimum time when using a constant Hamiltonian, thus constant Hamiltonians are time optimal for these constraints. We give an explicit formula for the time in these cases, in terms of the resource constraint. We show how our method produces a rich family of speed limit results, of which the generalized Margolus–Levitin theorem and the Mandelstam–Tamm inequality are special cases. We discuss the broader context of geometric approaches to speed limits in physical computation, including the way geometric approaches to quantum speed limits are a model for physical speed limits to computation arising from a limited resource.

scholarly journals A Study on the Effect of Intelligent Speed Adaptation (ISA) by Using Human Speech and the Acceptance

2018 ◽  
Vol 7 (4.27) ◽  
pp. 115
Author(s):  
Ahmad Khushairy Makhtar ◽  
Ahmed Khameini ◽  
. .
Keyword(s):  
Speed Limit ◽  
Important Criterion ◽  
Road Accidents ◽  
Traffic Fatalities ◽  
Bus Drivers ◽  
Speed Limits ◽  
Human Speech ◽  
Advisory System ◽  
Vehicle System ◽  
Intelligent Speed Adaptation

Intelligent Speed Adaptation (ISA) is an in-vehicle system that support drivers compliance with the speed limit. ISA is in fact a collective term for various different systems. Today, speeding was listed as the major cause of road accidents and traffic fatalities worldwide. By having a reliable and acceptable system that could alert the drivers about the speed limit in any particular areas, it will help in reducing the number of road accidents worldwide. This study was conducted to develop a system of Intelligent Speed Adaptation (ISA) by using GPS that would alert the bus drivers in UiTM Shah Alam about speed limits in any particular areas and it must be reliable and acceptable. This research is to determine the factors of acceptance from the drivers towards the ISA system. The system developed was an advisory system. Hence, the way this system give warning about the speed limit to the driver is an important criterion to be taken care of. The output parameter of for this study is the driver’s acceptance towards this ISA system and they must be happy to have this system inside their vehicles.  

Safe speed limits for a safe system: The relationship between speed limit and fatal crash rate for different crash types

2018 ◽  
Vol 19 (4) ◽  
pp. 404-408 ◽  
Author(s):  
Sam D. Doecke ◽  
Craig N. Kloeden ◽  
Jeffrey K. Dutschke ◽  
Matthew R. J. Baldock
Keyword(s):  
Speed Limit ◽  
Speed Limits ◽  
Fatal Crash ◽  
Crash Types ◽  
The Relationship

scholarly journals Speed Optimization vs Speed Reduction: the Choice between Speed Limits and a Bunker Levy

2019 ◽  
Vol 11 (8) ◽  
pp. 2249 ◽  
Author(s):  
Harilaos Psaraftis
Keyword(s):  
Greenhouse Gas ◽  
Ghg Emissions ◽  
Emissions Reduction ◽  
Speed Limit ◽  
Short Term ◽  
Speed Limits ◽  
Speed Reduction ◽  
Speed Optimization ◽  
Limit Option ◽  
Better Than

“Speed optimization and speed reduction” are included in the set of candidate short-term measures under discussion at the International Maritime Organization (IMO), in the quest to reduce greenhouse gas (GHG) emissions from ships. However, there is much confusion on what either speed optimization or speed reduction may mean, and some stakeholders have proposed mandatory speed limits as a measure to achieve GHG emissions reduction. The purpose of this paper is to shed some light into this debate, and specifically examine whether reducing speed by imposing a speed limit is better than doing the same by imposing a bunker levy. To that effect, the two options are compared. The main result of the paper is that the speed limit option exhibits a number of deficiencies as an instrument to reduce GHG emissions, at least vis-à-vis the bunker levy option.

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