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Rollover crash is a type of dangerous crash that occurs often in two-lane highways. Therefore, this study evaluates the effect of road shoulder and weather condition on rollover crashes. Crash data show that 8,609 crashes were recorded from 2006 to 2009 on six two-lane highways located at the center of Iran. This data contains 1860 rollover crashes. Rollover crash in this paper not included the head on crashes and fixed object crashes. Therefore the rollover crashes are only single vehicle crashes. Binary logit was selected for modelling since there were two possible outcomes: rollover crashes and other crash types. The variables of the final model include highway class, road shoulder width, as well as rainy, snowy, foggy and night conditions. The modeling results show that rainy and foggy variables, with coefficients of 0.731 and 0.719 respectively, had the greatest effects on rollover crash occurrence. Also, road shoulder width and night conditions, with coefficients of 0.221 and 0.184 respectively, had the least effects on rollover crash occurrence. Afterward, sensitivity analysis was performed on all the independent variables, and the results show variable variation and indicate that the probability of rollover crash occurrence is 21.29 % on the mentioned highway.

The aim of this research is to investigate the impact of crumb rubber and Styrene-Butadiene-Styrene (SBS) on rutting potential of porous asphalt mixtures. Optimal binder content of control mix, 5% SBS, and mixtures containing 10%, 15%, and 20% of crumb rubber were determined using Cantabro Loss test. Dynamic creep, wheel tracking, draindown, and fallinghead permeability tests were then carried out on specimens to examine rutting resistance, resistant to draindown, and permeability. SBS modified and 10% rubberized asphalt satisfied all the requirements of porous asphalt design criteria. They also have similar rutting performance, permeability. Except for rutting performance, 10% rubberized asphalt has the best performance. Instead, asphalt mixture containing 20% crumb rubber was the most mixture against rutting resistance.

The current study evaluated road crashes in three categories of drivers: passenger car drivers, heavy vehicle drivers and pickup truck drivers. The crash data of road crashes that occurred from 2009 to 2012 in Iranian suburban roads were analyzed. The crashes involved 194,041 damage, 9,677 injury and 1,303 fatality crashes. Because of the ordinal nature of crash severity, ordered logit model was selected for each vehicle driver category. In the passenger car driver category, the independent variables of driver’s gender, driver’s age and driver’s educational level (uneducated, less than high school diploma, high school diploma) were obtained for modeling; in the heavy vehicle driver category, the independent variables of driver’s age and driver’s educational level (uneducated, less than high school diploma) were obtained for modeling, and in the pickup truck driver category, the independent variables of driver’s age and driver’s educational level (uneducated, high school diploma) were obtained for modeling. The variable of driver’s gender with respect to passenger cars shows that crashes by female drivers are more severe than those involving male drivers in suburban roads. Regarding the variable of driver’s age, if the driver’s age increases in each vehicle driver category, the probability of occurrence of a severe crash will decrease. The variable of driver’s educational level shows that the severity of crashes involving a driver that has a low level of education is more compared with a driver that has a high level of education.

The present research studies the effectiveness and efficiency of solutions such as sodium chloride, magnesium chloride and potassium acetate on asphalt pavement to reduce the damage caused by moisture on asphalt pavement in winter. To prevent the stripping problem in asphalt, Nano-Zycotherm with three quantities corresponding to 0.1%, 0.2% and 0.3% weight of bitumen is used in this study. Under the saturated condition with the above solutions, the indirect tensile test performs by applying a freeze–thaw cycle as a means to measure the amount of moisture susceptibility. The results indicate that the asphalt mix containing 0.3% Nano-Zycotherm has a higher indirect tensile strength and tensile strength ratio than asphalt mix containing 0.1% and 0.2% Nano-Zycotherm. Accordingly, Magnesium chloride solution is the most effective deicing material to improve the indirect tensile strength and durability of asphalt pavements when faced with moisture and ice. Article highlights The presence of Nano-Zycotherm in asphalt leads to its increased resistance against stripping. The use of Sodium chloride and potassium acetate deicing solutions causes some damages in asphalt. Considering different solutions, magnesium chloride has the best performance against asphalt stripping.

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