seemingly unrelated regression equations for developing a pavement performance model

The paper presents a joint analysis of some pavement performance indicators based on a system of seemingly unrelated regression equations (SURE) which allows to handle correlated error terms. In particular, three major indicators such as the side friction coefficient (SFC20°C), mean-profile depth (MPD), and international roughness index (IRI), were measured in a case study and subsequently used in analysis. Regression parameters were estimated by the Maximum Likelihood Method and the t-statistic was considered to show the statistical significance of regression coefficients. The results show that estimation points have the signs expected: the SFC20°C decreases as the number of accumulated trucks (Nt) increases; whereas the MPD and IRI increase as the number of trucks increases. A likelihood ratio test was also carried out to determine whether the system model, which assumes correlation among error terms, was more appropriate than separate models. In this particular case, with three degrees of freedom, was found that the result corresponds to a p-value 0.150 and the null hypothesis cannot be rejected at any significance level less than this value.</p

Simulation of People Evacuation in the Event of a Road Tunnel Fire

AbstractThis paper presents basic findings obtained by means of a simulation model for representing an evacuation process from a curved bi-directional Italian road tunnel in the event of a fire. Simulations were carried out by using the STEPS people evacuation model associated with a CFD model simulating the fire. It was found that the evacuation time is primarily influenced by the walking time and to a less extent by the pre-movement time in all scenarios studied. The presence of an alarm system reduced the evacuation time for most the tunnel users, allowing them to reach the tunnel exit in safety

Le attività di ricerca del settore Strade, ferrovie ed aeroporti presso l'Ateneo di Salerno

GLI AGGIORNAMENTI DELL’ASSOCIAZIONE DEDICATA AL SETTORE DELLE INFRASTRUTTURE DI TRASPORTO AL FINE DI CREARE UN AMBITO ASSOCIATIVO IN CUI SOSTENERE E DIBATTERE DI PROBLEMATICHE SCIENTIFICHE, DIDATTICHE E CULTURAL

Evaluation of Stress and Strain Reductions in Orthotropic Steel Bridge Decks attributable to Asphalt Surfacing

The paper focuses on the structural behaviour of asphalt pavements on steel bridges and on the influence of the pavement on the reduction of stresses and strains in orthotropic decks. For this aim a simplified model has been proposed for evaluating the effects attributable to local bending of the steel deck. This model can be represented by a simply supported continuous plate that is made by the pavement, waterproofing, and deck. The pavement and waterproofing are considered to be an integral part of the structural deck system. Based on this model, a finite-element software was used for estimating stresses and strains both in the pavement and deck as a function of loads, temperatures, and dynamic modulus of asphalt mixture. The results showed that tensile stresses and strains at the bottom of the pavement due to the positive bending moment are higher than those at the top of the pavement produced by negative bending moment. The pavement contributed significantly towards reducing stresses and strains in the orthotropic deck by increasing the dynamic modulus of asphalt mixture. This means that a higher fatigue life of steel orthotropic decks might be expected. Thus, it is proposed that bridge designers should take these results into account

Delay Time Model at Unsignalized Intersections

A simulation process is presented for providing a point estimate of average traffic delay on minor roads at urban unsignalized intersections during peak hours. A performing process of microsimulation was carried out, and a good level of conformity was obtained between the traffic simulated in the peak hours and the corresponding amount of traffic measured in the field. Traffic performance measures expressed in terms of average delay suffered by vehicles on minor roads were used in the statistical analysis. A negative binomial regression model, jointly applied to conflict traffic volume (VHPc) and traffic volume entering intersection from minor roads (VHPe), was used to model the average delay. A dummy variable D was also introduced to test the adequacy of the regression model through the range of hourly conflict traffic volumes. Regression parameters were estimated by the maximum likelihood method and the significance of the covariate was evaluated by using the likelihood ratio test (LRT). The results show that the average delay on minor roads is positively associated with VHPc, VHPe, and D, and these variables are all statistically significant. The regression model was found to fit well the average delays computed in simulation. Additionally, a stop-time model and a maximum queue length model were also developed

EXPERIENCE WITH SIGNIFICANT INCIDENTS IN ROAD TUNNELS

This report can be used as a reference to further improve the integrated approach to tunnel safety, especially the requirements and key aspects to data collection and risk assessment in this approach

PREVENTION AND MITIGATION OF TUNNEL-RELATED COLLISIONS

This report focuses on measures to prevent or mitigate tunnel-related collisions, for both existing and new tunnels

Crash Prediction Models for Roads Including Rainfall and Hazardous Points

Predictive models for multilane roads including also the effects of rainfall and hazardous points on the crash frequency are presented in this paper. Accident data observed on a specific motorway during a period of eight years were used in statistical analysis. Negative Binomial Distribution, was applied for modelling the random variation of the crash data. Model parameters were estimated by Maximum Likelihood Method, and the Generalised Likelihood Ratio Test was used to detect the significant variables to be included in the final model. Separate prediction models for curves and tangents are proposed. For curves, it is found that the crash frequency is positively associated with the following variables: length (L), curvature (1/R), and the presence of hazardous points such as junctions (J) or tunnels (T); whereas for tangents with L and T. The effect of rain precipitation shows that with a wet pavement significant increases in crash frequency are expected, more especially on curves compared to tangents. This might be due to the combined effect of rain and centrifugal force in curve