Search

Speed limits are a common traffic regulation for balancing traffic mobility and safety on roadways. Speed transition zones bear complicated driver behaviours. However, driver behaviours are even more complex when speed transition zones are dynamically created and shifted by variable speed limits (VSLs). Much existing research has estimated long-term driver compliance, evaluated effectiveness of speed enforcement, and attempted to involve compliance into VSL control algorithms. Whereas, limited research provides convincing solutions for representing speed limit effect and estimating real-time driver compliance at speed transition zones. To fill this research gap, this paper analyses field data from two speed transition zones along southbound of 97th Street, Edmonton, Canada. Temporal and spatial variations of speed and driver compliance are investigated in detail using statistical tests. A linear regression is then established to rank the contributions of the selected factors. Finally, some suggestions and guidelines for VSL algorithm design and implementation are proposed. Key words: speed limit, driver compliance, speed transition zones, speed education. Les limites de vitesse constituent une regulation du trafic courante ayant pour but d'equilibrer la mobilite du trafic et la securite routiere. Les zones de transition de vitesse entrainent des comportements compliques chez les conducteurs. Cependant, les comportements des conducteurs sont encore plus complexes lorsque des zones de transition de vitesse sont creees dynamiquement et changees au moyen de limites de vitesse variables (<>). Une bonne partie de la recherche actuelle a estime le respect du code de la route par les conducteurs a long terme, evalue l'efficacite de l'application des limites de vitesse et tente d'incorporer le respect dans les algorithmes de flux de commande des VSL. Neanmoins, peu de recherches fournissent des solutions convaincantes qui representent l'effet des limites de vitesse et evaluent le respect des conducteurs en temps reel aux zones de transition de vitesse. Afin de combler ce manque de connaissances, cette etude analyse les donnees de terrain de deux zones de transition de vitesse le long de la <> a Edmonton au Canada. On examine en detail les variations temporelles et spatiales de la vitesse et le respect des conducteurs, et ce, en utilisant des tests statistiques. Une regression lineaire est ensuite etablie afin de classer les contributions des facteurs selectionnes. Finalement, on donne des suggestions et des directives pour la conception et la mise en reuvre d'algorithmes de VSL. [Traduit par la Redaction] Mots-cles: limite de vitesse, respect du code de la route par les conducteurs, zone de transition de vitesse, education routiere en matiere de vitesse., 1. Introduction Speed limits provide the legal maximum or minimum speeds on roadways. Appropriate speed limits balance traffic mobility and safety concerns. In turn, roadway mobility and safety performance depends [...]

Variable speed limit (VSL) is becoming recognized as an effective way to improve traffic throughput and road safety. In particular, methods based on traffic state prediction exhibit promising potential to prevent future traffic congestion and collisions. However, field observations indicate that the traffic state prediction model results in nonnegligible error that impacts the next step decision making of VSL. Thus, this paper investigates how to eliminate this prediction error within a VSL environment. In this study, the traffic state prediction model is a second-order traffic flow model named METANET, while the VSL control is model predictive control (MPC) based, and the VSL decision is discrete optimized choice. A simplified version of the switching mode stochastic cell transmission model (SCTM) is integrated with the METANET model to eliminate the prediction error. The performance of the proposed method is assessed using field data from a VSL pilot test in Edmonton, Canada, and is compared with the prediction results of the baseline METANET model during the road test. The results show that during the most congested period the proposed SCTM-METANET model significantly improves the prediction accuracy of regular METANET model., 1. Introduction The VSL control method was designed to keep the credibility of speed limits even under adverse conditions such as congestion and bottleneck road segments, so that the speed [...]

Adverse weather has significant impacts on road conditions and traffic dynamics. It is observed that adverse weather as a set of exogenous factors lowers the free flow speed, shifts critical density, decreases flow capacity, and makes the freeway more prone to congestion. This paper proposes a weather factor model to be plugged into a macroscopic traffic prediction model, so that under bad weather traffic variables can be more accurately and reasonably estimated and predicted for traffic control use. To be specific, weather-specific fundamental diagrams are built by introducing weather factors to free flow speed, capacity, and critical density. The weather factors are modelled by selected weather measurements. Weather factor parameters are trained by recent historical weather and traffic data and then can be put into real-time macro traffic prediction and control. The traffic prediction model in the case study is METANET model, in which fundamental diagram parameters are one source of input. The weather-specific prediction error and conventional prediction error are compared. Real data collected by loop detectors on Whitemud Drive, Edmonton, Canada, is used for parameter calibration and prediction error evaluation. The results show that the proposed weather models reasonably improved the accuracy of macro traffic state prediction model compared to conventional model., 1. Introduction Over the past two decades, the focus of efforts in modelling and forecasting macroscopic traffic states has transitioned from univariate temporal correlation to multivariate temporal-spatial correlation and from [...]

Hydrodeoxygenation(HDO) of methyl heptanoate was performed overzirconia-supported mono- and bimetallic Rh and Pt catalysts in a batchreactor. The Rh/ZrO2catalyst gave the highest conversionand selectivity toward hydrocarbons (dominantly hexane) at 250 °Cand 8 MPa of H2. The formation of alkenes was not detecteddue to high hydrogenation activity of the noble metal catalysts. Furthermore,a complete reaction network for the HDO of methyl heptanoate overRh/ZrO2was proposed on the basis of the HDO experimentswith reaction intermediates, such as heptanoic acid, heptanal, andheptanol. It was proposed that heptanoic acid originated from thedirect hydrogenolysis of methyl heptanoate. The prevailing reactionpathway to hexane was suggested to be decarbonylation reaction fromeither heptanoic acid or heptanal. Heptanal was highly reactive onRh catalyst in the presence of H2. The effect of reactiontemperature on the HDO of methyl heptanoate over Rh/ZrO2was also investigated. Increasing temperature significantly improvedthe conversion of methyl heptanoate and the selectivity toward hydrocarbons. [ABSTRACT FROM AUTHOR]