The enforcement of speeding: should fines be higher for repeated offences?

Speed limits are a well-known instrument to improve traffic safety. However, speed limits alone are not enough; there is need for enforcement of these limits. When one observes fine structures for speed offences one often finds two characteristics. First, the fine increases with the severity of the violation. Secondly, the fine depends on the speeders' offence history. We focus on this last point and confront two fine structures, both increasing with speed: a uniform fine and a differentiated fine, which depends on the offence history. Drivers differ in their propensity to have an accident and hence in their expected accident costs. Literature then prescribes that the fine for bad drivers should be higher than for good drivers. However, the government does not know the type of the driver. We develop a model where the number of previous convictions gives information on the type of the driver. We find that the optimal fine structure depends on the probability of detection and on the strength of the relationship between the type and having a record. We illustrate this by means of a numerical example.

Catching or Fining Speeders: A Political Economy Approach

According to Becker (1968) it is best to use very high fines and low inspection probabilities to deter traffic accidents because inspection is costly. This paper uses a political economy model to analyse the choice of the fine and the inspection probability. There are two lobby groups: the vulnerable road users and the ‘strong’ road users. If only vulnerable road users are effective in lobbying, we find that the expected fine is higher than if only the interests of car drivers are taken into account. When we consider the choice between inspection probability and the magnitude of the fine for a given expected fine, we find that the fine preferred by the vulnerable road users is higher than socially optimal. The reverse holds if only the car drivers are effective lobbyists. The orders of magnitude are illustrated numerically for speeding and contrasted with current fines for drunk driving in the European Union.Political economy, enforcement, traffic safe

Catching or fining speeders: a political economy approach

According to Becker (1968) it is best to use very high fines and low inspection probabilities to deter traffic accidents because inspection is costly. This paper uses a political economy model to analyse the choice of the fine and the inspection probability. There are two lobby groups: the vulnerable road users and the ‘strong’ road users. If only vulnerable road users are effective in lobbying, we find that the expected fine is higher than if only the interests of car drivers are taken into account. When we consider the choice between inspection probability and the magnitude of the fine for a given expected fine, we find that the fine preferred by the vulnerable road users is higher than socially optimal. The reverse holds if only the car drivers are effective lobbyists. The orders of magnitude are illustrated numerically for speeding and contrasted with current fines for drunk driving in the European Union.Political economy, enforcement, traffic safety

Catching or fining speeders: A political economy approach.

According to Becker (1968) it is best to use very high fines and low inspection probabilities to deter traffic accidents because inspection is costly. This paper uses a political economy model to analyse the choice of the fine and the inspection probability. There are two lobby groups: the vulnerable road users and the ‘strong’ road users. If only vulnerable road users are effective in lobbying, we find that the expected fine is higher than if only the interests of car drivers are taken into account. When we consider the choice between inspection probability and the magnitude of the fine for a given expected fine, we find that the fine preferred by the vulnerable road users is higher than socially optimal. The reverse holds if only the car drivers are effective lobbyists. The orders of magnitude are illustrated numerically for speeding and contrasted with current fines for drunk driving in the European Union.Investment; Pricing; Decisions; Decision; Transport; Economy;

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Incorporating unsteady flow-field effects in flamelet-generated manifolds

In general, simulating combustion can be a very costly job. This is caused by the large number of chemical reacting species that are strongly coupled. Moreover, all the (chemical) time-scales that are present, span a multitude of orders, which results in a very large, stiff system of strongly coupled, nonlinear equations and solving such a system is very CPU-intensive. Fortunately, it appears that many combustion systems are dominated by a handful of (slow) processes only. This is due to the fact that the fastest processes rapidly become exhausted and therefore are often neglected. This has subsequently led to a number of reduction techniques that take advantage of the observation that combustion can often be predicted reasonably accurate by taking only a small number of time-scales into account. In this thesis a reduction technique that was introduced by van Oijen [61], i.e., Flamelet- Generated Manifolds (FGM), is expanded upon. The main goal of this thesis is to study whether unsteady flow effects can be captured within the Flamelet-Generated Manifolds concept. The flames that are studied are one-dimensional, non-premixed, stagnation flames and although FGMwas initially developed for and successfully applied to premixed flames but in principle it can also be applied to non-premixed flames. To that end, first a unified one-dimensional flame model is presented, which can be used to describe (partially) premixed and non-premixed flames. Such a one-dimensional flame model is often referred to as flameletmodel. The first step is to decompose the combustion process into three distinct sub-problems, i.e., 1) fluid motion and mixing of enthalpy and elements, 2) the flame front dynamics and 3) the dynamics of the internal flame structure embedded within this flame front. When flames are considered, it is often useful to use a so-called flame adapted coordinate system, where coordinate surfaces correspond to flame surfaces. The flame front dynamics can be described by the evolution of these flame surfaces, which correspond to iso-surfaces of a so-called principal controlling variable Y, for which a conservation equation can be solved. Applying such a coordinate transformation, leads to a set of quasi-one-dimensional combustion equations, which serve as the basis of the FGM method. Generally it is assumed that perturbations from one-dimensional flame behavior are small, and can therefore be neglected. In order to numerically assess these assumptions, the species conservation equation is subdivided into several individual contributions, i.e., an unsteady term, normal transport, flame stretch, curvature, tangential diffusion and the chemical production and consumption terms, respectively. Three different twodimensional flames are simulated, one unsteady premixed flame, one unsteady nonpremixed flame and one steady non-premixed flame. Using the numerical results from these detailed flame simulations, the individual contributions of the species conservation equations are computed and compared to each other. The results show that besides normal transport and chemistry, flame stretch rate and curvature can also be important in both premixed and non-premixed flame simulations. From the two unsteady flame simulations it also follows that the unsteady contribution can be significant. Furthermore, for the steady non-premixed flame, two different principal controlling variables were chosen, resulting in two different coordinate transformations, i.e., a typical non-premixed flame-adapted coordinate system and a typical premixed one. This is possible due to the fact that the flamelet model derived in this thesis is a unified flamelet model, which is able to describe both (partially) premixed flames as well as non-premixed flames. To study whether the effect of transient, local flow fluctuations can be captured by the FGM approach, both steady and unsteady non-premixed flamelet simulations with a detailed chemistry model are studied. Two different situations are studied, 1) a flame which is significantly strained but still far away from the steady extinction limit and 2) a flame where the applied strain-rate is near or even beyond the steady extinction limit. For both situations, two different Flamelet-Generated Manifolds are constructed, i.e., one based on a set steady flamelet simulations and one based on a set of unsteady flamelet simulations. The chemical compositions found during the steady flamelet simulations form a two-dimensional manifold in composition space. On the other hand, a detailed analysis of the chemical compositions found during the unsteady flamelet simulations shows that the unsteady flamelet simulations form a three-dimensional manifold in composition space. Both manifolds are applied to simulate one-dimensional flames that are subjected to sinusoidally varying strain-rate. The results of both FGM simulations are compared to an unsteady simulation with a detailed chemistry model. Both local observables, like species mass fractions and temperature for example, as well as flamesurface area properties like the integral source-term, are represented well with both manifolds. However, for species that are related to the slowest time-scales it is shown that a three-dimensional manifold may result in less accurate predictions, and more controlling variables may be needed

The effect of quenching and defects size on the HCF behaviour of Boron steel

This work investigates the effect of natural and artificial surface defects and quenching on the fatigue strength of a Boron steel (22MnB5). A vast experimental campaign has been undertaken to study the high cycle fatigue behaviour and more specifically the fatigue damage mechanisms observed in quenched and untreated materials, under different loading conditions and with differents artificial defects sizes (from 25 μm to 370 μm radius). In order to test the sheet metal in shear an original test apparatus is used. The critical defect size is determined to be 100 ± 50 μm. This critical size does not appear to depend on the loading type or the microstructure of the material (i.e. ferritic–perlitic or martensitic). However, for large defects, the quenched material is more sensitive to the defect size than the untreated material. For a defect size range of 100–300 μm the slope of the Kitagawa–Takahashi diagram is approximately −1/3 and −1/6 for the quenched and untreated materials respectively. A probabilistic approach that leads naturally to a probabilistic Kitagawa type diagram is developed. This methodology can be used to explain the relationship between the influence of the heat treatment and the defect size on the fatigue behaviour of this steel