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Providing an appropriate length of highway entrance ramps is an important feature that should be considered in freeway design. The recommended minimum acceleration lane length in the Green Book of the American Association of State Highway and Transportation Officials (AASHTO) is currently used for designing entrance ramp terminals. However, in some cases, traffic congestion and crashes are observed when heavy trucks enter freeways, which indicates they could not accelerate enough and did not reach the merge speed at the end of the acceleration lane. Therefore, several scenarios were simulated using a dynamic simulation model (TruckSim) for heavy vehicles with weight to power ratios of 61, 67, 86, and 108 (kg/kW) and grades of zero, ±3, and ±5%. Subsequently, a linear regression model was presented to calculate acceleration lane lengths. The results showed that the acceleration rate of heavy vehicles is not adequate, especially in upgrades. For example, at +5% upgrades, heavy trucks cannot accelerate to the merge speed mentioned in the AASHTO. Conversely, the acceleration rate of heavy vehicles increased in downgrades; therefore, some heavy vehicles were able to achieve merge speed along the proposed length of AASHTO.

High collision rates on horizontal curves compared with other roadway elements make them one of the most critical elements in a transportation network and thus good candidates for new studies, especially of the stability of a vehicle driving on a horizontal curve. In this regard, spiral transition curves as facilities to enter horizontal alignments are very important. While the superelevation changes in these curves have always been linear, the aim of this study was to evaluate non-linearity in the superelevation attainment function (SAF). Various scenarios were used in order to cover different situations. As a simulation tool, the CarSim software package was used to model three kinds of passenger cars (sport utility vehicle, utility truck and sedan). In addition, 16 types of spiral–curve–spiral road plans for three different conditions of road slope, six types of warping in the SAF and two types of functional speed were examined (a total of 1728 scenarios). The results showed that non-linearity might produce better results than other proposed methods; for example, it was found that a parabolic function reduced the lateral acceleration rate by over 50% for high superelevation and design speed. [ABSTRACT FROM AUTHOR]

Reverse Horizontal Curves (RHCs) are among the most accident-prone road points, with many annual fatalities and injuries. These fatalities can increase dramatically if the RHCs and longitudinal slopes are combined. The importance of increasing the safety of RHCs, especially in mountainous routes, is doubled due to the possibility of combining RHCs with vertical extensions or combining them with so-called steep slopes. This study used vehicle dynamic modeling to evaluate the lateral friction of various vehicles. Including the E-Class Sedan, E-Class SUV, Truck, and Bus, moving on RHCs combined with a longitudinal slope (downgrade, upgrade, and direct distance). Then, the RHC lateral friction model was presented using the multiple regression model based on the effective parameters, including design speeds, direct distance, and different longitudinal slopes. The results showed that speed, longitudinal slope, and vehicle type had the most impact, and direct distance had the most negligible impact in friction coefficient models. Based on the modeling results, the higher the design's speed and the shorter the direct distance, the lower the lateral friction coefficient for the Sedan and SUV. Hence, the safety of the vehicles is greater. For trucks, reduced speed, increased direct distance, and reduced slope led to increased safety. In the results, the most critical state was the lateral friction coefficient at a speed of 80km/h and a direct distance of 116m for the SUV., Author(s): Maziyar Khanjari (corresponding author) [1]; Ali Abdi Kordani [2]; Saeed Monajjem [3] 1. Introduction The road factor, along with both human and vehicle factors, plays an influential role in [...]

Freeze-Thaw Damage (FTD) is one of the most important factors that can reduce the Warm Mix Asphalt's (WMA) crack resistance. In this study, modified WMA and WMA mixtures' fracture behavior containing vertical and angular cracks was evaluated using semi-circular bend geometry (SCB). For this purpose, SCB samples containing vertical cracks (Pure mode II) and angular cracks (Pure mode I) were made first; Then, FTD conditions were applied to the samples to condition them. The results showed that all the mixtures modified with Calcium Lignosulfonate (CL) and polyester fibers (PE) had a better crack resistance than the base sample under FTD conditions. As a result, the fracture energy of WMA mixtures containing 6% CL increased by about 146, 141, 75, and 93%, respectively, while the fracture toughness of WMA mixtures containing 3% CL increased by about 103, 95, 97, and 92%, respectively. The results of the brittleness indices showed that mixtures containing 6% CL, 0.25% PE-6% CL, and 0.25% PE had a more flexible behavior than other mixtures under FTD conditions, respectively. Therefore, using these mixtures, in addition to improving the fracture performance, was also recommended for environmentally friendly purposes. [ABSTRACT FROM AUTHOR]

The importance of the baggage claim area as the gateway to the city is extremely high. Therefore, the initial impression of the quality of services provided at the destination airport is based on this area. In this research, an agent-based and discrete event approach using five parameters (speed and traffic of passengers, speed and arrangement of carousels, and air traffic) was applied in order to simulate passenger flow in the baggage claim area of Imam Khomeini International Airport, Tehran, Iran. In this regard, forty-eight scenarios were identified and simulated using AnyLogic software, and the waiting time and level of service for each scenario were obtained. Finally, it was revealed that changing the arrangement of the carousels from T-shaped to oval-shaped and expansion of the circumference by 10% had the greatest effect. Also, changing the speed of the carousels had the least influence on increasing the level of service and reducing waiting time. [ABSTRACT FROM AUTHOR]

Horizontal curves, as one of the most accident-prone parts of the road, have always attracted special attention. When a vehicle is moving on a road, the driver has to be constantly on the lookout for small deviations from the main route, possibly due to disturbances such as wind, road roughness, and unwanted entrances by the driver. These types of deviations have a corrosive effect on the driver and will eventually lead to the overturning and slipping of vehicles, so they should be minimized. AASHTO standard procedures, as the most valid road design bylaw, do not consider the effect of lateral wind, in which the effect of lateral wind in arcs has been investigated in this research. The work conducted in this research is to increase knowledge about the directional stability of vehicles that are affected by strong winds and to investigate the parameters of the study using accurate models of dynamic simulation of vehicles that are subject to winds. This study aimed to increase the understanding of vehicle sensitivity to wind due to strong lateral winds. For this purpose, the process of passing different types of vehicles through horizontal arcs in different longitudinal slopes with different velocities of the vehicle under lateral wind is simulated and the mechanical properties of vehicles under such conditions are calculated to compare with the results obtained from the passage of vehicles through a smooth horizontal arc (without longitudinal slope) and without lateral wind. Overturning angle, slip angle, lateral acceleration, and lateral coefficient of friction of vehicles in this study were calculated through software outputs, and the effect of lateral wind on the safety of arcs has been investigated. [ABSTRACT FROM AUTHOR]

An understanding of the change in follower behaviour as a driver characteristic in traffic simulations is necessary because these behavioural changes are frequently observed in traffic oscillations. The change in follower behaviour due to traffic acceleration and deceleration waves can be classified according to different behavioural patterns resulting from different driver reactions. Combinations of existing behavioural patterns (under-reaction–timid, over-reaction–timid and constant over-reaction–timid patterns) were thus analysed. The method of analysis was based on an artificial neural network model at the microscopic level in order to simulate the extent to which follower behaviour deviates from Newell's car-following model. The most influential parameters of all the behavioural patterns were determined. Based on the under-reaction–timid pattern, decreasing the reaction speed resulted in a change in behaviour due to the development of safe spacing at the reaction point. In addition, follower spacing was the most influential in the over-reaction–timid pattern, resulting in increasing and then decreasing behavioural change. In the constant over-reaction–timid pattern, the follower's speed resulted in increasing and then decreasing the change in behaviour. The application of behavioural change to an intelligent transportation system would improve safety. [ABSTRACT FROM AUTHOR]

Steep downgrades are known as a part of mountain roads with a significant number of severe crashes. Generally, using speed limiters such as speed bumps and speed humps are considered the most effective (considering both the time and cost) ways to reduce the number of victims. The efficiency of speed limiters depends on the driver's consciousness and the car's braking system; the latter could be problematic in wet and dark conditions of the road. The main goal of the current study is to propose an approach to correct the longitudinal profile of roads by replacing the consecutive downgrades and upgrades with a continuous downgrade. The vehicle's speed is reduced by using this method before entering an accident-prone site without the driver's involvement and breaking. To this end, a well-known software program is used under two speeds (70 and 100 km/h) in 68 different routes to analyze speed along the proposed routes. Also, another computer model is used for dynamic simulation. Dynamic analyses and regression models show that the vehicle's speed in the new proposed route is significantly reduced compared with the continuous downgrade. Moreover, results indicate that the upgrade slope of the proposed route has the most impact on reducing the final speed of the vehicles. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The aim of this study is to assess and predict the effects of on-street parking cost elasticity on the mode choice behaviour of motorists. The stated preference method was used for data collection in the central business district of Qazvin, Iran, and the mode choice behaviour of motorists was modelled through different pricing scenarios. Using a multinomial logit model, it can be concluded that the price value of the motorist's car, car ownership per household, hourly parking rate, maximum hourly parking rate that the users are willing to pay, trip purpose and the education level of the users are significant in users' mode choice utility due to pricing. The results have indicated that by increasing the parking hourly rate from 500 to 60 000 IRR (Iranian Rial), 74% of users will shift their modes from private cars. Shares of choosing a taxi or bus will increase 28 and 18%, respectively. [ABSTRACT FROM AUTHOR]

Speed humps are in widespread use around the world. Despite their effective performance in increasing safety, they cause considerable damage to vehicles and discomfort to drivers and passengers. This paper investigates the dynamic response of vehicles on different types of speed humps using a multibody simulation software package that is popular in the automotive industry. Following this evaluation, two new profiles are recommended to optimize the dynamic performance of speed humps. A series of formulas are also presented to estimate the dynamic performance of passenger cars on flat-topped and parabolic humps based on vehicle speed, hump dimensions, and driving behavior while traversing the hump. The results show that, for flat-topped humps, the ramp length (or entrance slope) has the greatest effect on vehicle performance. It is found that the dynamic performance of the recommended profiles is much better than that of conventional humps. [ABSTRACT FROM AUTHOR]

The use of fibers and polymers in asphalt mixtures leads to improved quality, higher lifespan, and lower maintenance costs by making mechanical, physical, and chemical changes. This results in eliminating or reducing the weaknesses of mixtures in the production, implementation, and service phases. In this study, the Stone mastic asphalt mixtures with the same gradation curve, but different additives are evaluated. In the first, second, and third groups of experiments, SEBS elasto-plastomer polymer (SEBS), SEBS elasto-plastomer polymer with cellulosic fibers (SEBS-CF), and SBS elasto-plastomer polymer with cellulosic fibers (SBS-CF) were added to the mixture in various weight percentages, respectively. Also, Stone mastic asphalt mixtures without any additives (SMA-S) and SBS-modified mixtures (SBS) as the most common modifiers were considered as the control mixtures. To evaluate the designated mixtures related to moisture sensitivity, several tests including saturated marshal, indirect tensile strength, resilient modulus, and drain down tests were applied. The results showed that the designated asphalt mixtures meet the requirements for the moisture sensitivity and resilient modulus tests successfully, and it is concluded that among these samples of mixtures, 4% SEBS has the best performance compared to other mixtures; it had even better performance than the SBS mixtures, which are the most common modifiers. Therefore, this issue can be a great help considering the advantages of this polymer over other modifiers to select and use it to modify asphalt mixtures among the mixtures although SEBS-CF had a higher percentage of optimum bitumen achieved less drain down, which shows that the bitumen of these mixtures has become more behaviorally stable due to modification with polymer and fiber at the same time. [ABSTRACT FROM AUTHOR]

The aim of this research was to predict operating speed by considering geometric and roadside factors. Although most previous studies have employed linear regression modelling (LRM) to predict operating speed, this study recommends structural equation modelling (SEM) for the prediction of operating speed on rural multi-lane highways. In addition to geometric variables, LRM takes roadside variables into account. When employing SEM in this work, two latent variables were defined, namely 'roadside effects' and 'geometric effects'. The first latent variable was the combination of land-use type, land-use density and number of accesses per segment, while the second was extracted from the segment length, highway grade, curvature, the presence of a guardrail and flat roadside slope, and the posted speed limits. The residual analysis and R2 values for LRM and SEM suggest that SEM demonstrates superior modelling performance compared with LRM. These results show the significant role of latent variables in predicting speed, which cannot be achieved through ordinary LRM. [ABSTRACT FROM AUTHOR]