Search

Traffic metering parameters in the CBD of Akure such as traffic composition and volume-capacity ratio were collected and evaluated to determine the levels of service of the selected major roads namely Oba Adesida road (directions A and B): direction A from Cathedral junction to 'A' Division and Direction B from 'A' Division to Cathedral junction and Arakale road (directions C and D): direction C from Isikan roundabout to NEPA roundabout and direction D from NEPA roundabout to Isikan Roundabout. The traffic composition analysis revealed the passenger car/taxi as the predominant mode while poor parking system, trading activities along the carriageway, bad roads, construction activities were identified as factors affecting the levels of service. [ABSTRACT FROM AUTHOR]

The heterogeneity of vehicle types and their lane-free movement are the unique characteristics of mixed traffic conditions. Modelling and controlling such a traffic system is challenging. Towards this, to overcome the adverse effects of heterogeneity, segregation of traffic based on vehicle type is the viable solution proposed in this study. Two mathematical formulations are developed for multi-class segregation problems to identify a vehicle type or a combination of vehicle types to be segregated from the remaining traffic to enhance efficiency and safety in mixed-traffic networks. The corresponding objectives are related to minimising the total system travel time and network crash risk. The developed models were evaluated using a real-world mixed traffic network case study and it was observed that the total system travel time savings were 10% compared to the case of conventional traffic assignment. Sensitivity analysis shows that the segregation patterns are repeatable across compositions, demands, and parameter values. Based on the observations, a heuristic solution is proposed for the multi-class vehicle segregation problem. The heuristic solution involves routing different vehicle types in the network, and the evaluation results showed that the heuristic method could provide a good trade-off solution with respect to efficiency and safety. Considering the extreme point solutions of the two single-objective formulations, the total system travel time value is 11% higher than the single objective case of travel time and the total crash risk is 90% higher than the single objective case of crash risk. The findings in this paper are expected to improve the modelling and traffic assignment strategies for mixed traffic networks by addressing their unique characteristics.

Passenger Car Unit (PCU) is a relative weightage factor given to the traffic volume of individual vehicle category to deal with the heterogeneity in a mixed traffic situation. Ample volume of studies was conducted till date to estimate PCU of different vehicle categories. This paper discusses the methodologies adopted in these studies for estimation of PCU and analyses the advantages and limitations of each method. A number of researchers proposed static values of PCU while some of them realized its dynamic aspects. These studies also examined how PCU is changing with traffic characteristics, road geometrics and other factors. The present review found that PCU recommended in literature are region specific (traffic characteristics and driving culture vary across nations) resulting in high inconsistency in the outcome. Inconsistency was found not only in the range of PCU but also in the trend how it is varying with other governing factors. This paper provides a categorical summary of the research outcome in the domain of PCU estimation on urban roads.

Saturation flow rate is very important parameter which was used extensively in the design and control of signalized intersections. In the present study saturation flow is estimated with cycle time, approach width, proportion of two wheelers, proportion of three wheelers and proportion of cars using regression analysis and Artificial Neural Networks. A comparison of MLR and ANN prediction of field saturation flow is made, and the study results showed that ANN are highly accurate because of their self-computing and intelligent behaviour. Mean absolute percentage error (MAPE) value is less and Index of Agreement (IA) value is high for best fitted ANN model when compared to those for MLR and INDO HCM models. The developed ANN satisfactorily predicted the saturation flow at signalized intersections in mixed traffic conditions with MAPE of 1.76% and with IA of 0.999. [ABSTRACT FROM AUTHOR]

Majority of the existing studies on passenger car unit (PCU) estimation are limited to inter-urban and divided urban roads. The characteristics of traffic on undivided urban roads are completely different from those on divided roads. This study aims to estimate the PCU values on undivided urban roads with varying traffic conditions. Estimation of PCU requires speed information for individual vehicle categories. Hence, a universal Kriging-based speed prediction model was developed and utilized for PCU estimation. The model was constructed based on the classified traffic volume and speed data that were collected by videography method on undivided urban road segments in different cities in India. The proposed model was utilized to study the effects of traffic volume, traffic composition, and carriageway width on PCU. An alternative approach of 'Stream Equivalency Factor' has also been suggested in this paper. Use of this approach can simplify the process of determining the homogeneous equivalent of a mixed traffic flow. [ABSTRACT FROM AUTHOR]

Gap acceptance method used in the analysis of two-way stop-controlled intersections is based on the assumption that major street traffic is uninterrupted. However, the present study found a clear difference among the traffic characteristics of the major street at the intersection and upstream of it. The distributions of inter-arrival times and speeds of major street vehicles are significantly modified as they approach the intersection. Data collected from five intersections in India were used to estimate the critical gaps for motorized two-wheelers and cars executing two non-priority movements (right turn from major and minor streets). Critical gap, estimated using occupancy time method, was found to vary among intersections, even when they were similar in geometry. This is attributed to the proportion of large-size vehicles in the conflicting traffic. A statistically strong relation is found between the critical gap of a vehicle type and the proportion of large-size vehicles in the conflicting traffic. [ABSTRACT FROM AUTHOR]

Vehicles generally move in the form of platoons after discharging from the stop line of signalized intersection. While moving toward the downstream signal, due to the interaction between moving vehicles, road geometry, traffic composition and their speed difference, platoons get dispersed. Dispersion of platoon influences signal co-ordination, arrival pattern, turning maneuver at upstream signal. Moreover, while designing the intersection under mixed traffic scenario, platoon dispersion is important to create a link between traffic signals. Therefore, the present study is taken up with the objective of estimating the platoon dispersion distance after crossing the stop line. A model is developed based on the simulated data sets. VISSIM, a micro-simulation software, is used to replicate the field traffic conditions. To ensure the applicability of the model in the existing mixed traffic conditions, two different methods were used. Firstly, data were collected from two sites and used for validating the performance of the model. The results indicated a good match (maximum 9% error) between the field-observed and model-estimated platoon dispersion distance. Secondly, the traffic scenario alike the two study sites was created in VISSIM and the simulated and field-observed data sets were compared to check how accurately VISSIM can replicate the existing mixed traffic conditions. It is observed that VISSIM had replicated the field conditions with a maximum error of 10%. Therefore, the output of the study indicates that the proposed model may be used to estimate the platoon dispersion distance with reasonably high accuracy under mixed traffic conditions. [ABSTRACT FROM AUTHOR]

In a build-operate-transfer (BOT) highway project, pavement roughness progression generally has a direct impact on the highway maintenance cost and user costs. Given two common rehabilitation strategies, this study respectively investigates the optimally designed highway capacity and tolls of multi-type vehicles in Pareto-efficient contracts. Under supplementary conditions, it proves that the optimal toll revenue could fully cover the highway construction and maintenance cost in these contracts, no matter with or without the regulated traffic composition. Further extensions are made to evaluate and identify properties of the highway v/c ratio, rehabilitation period or critical roughness under the two rehabilitation strategies, respectively. [ABSTRACT FROM AUTHOR]

Mobile monitoring and computational fluid dynamics (CFD) modeling are complementary methods to examine spatio-temporal variations of air pollutant concentrations at high resolutions in urban areas. We measured nitrogen oxides (NOx), black carbon (BC), particle-bound polycyclic aromatic hydrocarbons (pPAH), and particle number (PN) concentrations in a central business district using a mobile laboratory. The analysis of correlations between the measured concentrations and traffic volumes demonstrate that high emitting vehicles (HEVs) are deterministically responsible for poor air quality in the street canyon. The determination coefficient ( R2) with the HEV traffic volume is the largest for the pPAH concentration (0.79). The measured NOx and pPAH concentrations at a signalized intersection are higher than those on a road between two intersections by 24% and 25%, respectively. The CFD modeling results reveal that the signalized intersection plays a role in increasing on-road concentrations due to accelerating and idling vehicles (i.e., emission process), but also plays a countervailing role in decreasing on-road concentrations due to lateral ventilation of emitted pollutants (i.e., dispersion process). It is suggested that the number of HEVs and street-canyon ventilation, especially near a signalized intersection, need to be controlled to mitigate poor air quality in a central business district of a megacity. [ABSTRACT FROM AUTHOR]

The effects of traffic mix (the percentage of cars, trucks, buses and so on) are of particular interest in the speed-volume relationship in urban signalized arterials under various geometric and control characteristics. The paper presents some empirical observations on the relation between travel speed, traffic volume and traffic composition in urban signalized arterials. A methodology based on emerging self-organizing structures of neural networks to identify regions in the speed-volume relationship with respect to traffic composition and Bayesian networks to evaluate the effect of different types of motorized vehicles on prevailing traffic conditions is proposed. Results based on data from a large urban network indicate that the variability in traffic conditions can be described by eight regions in speed-volume relationship with respect to traffic composition. Further evaluation of the effect of motorized vehicles in each region separately indicates that the effect of traffic composition decreases with the onset of congestion. Moreover, taxis and motorcycles are the primary affecting parameter of the form of the speed-volume relationship in urban arterials.

Mixed traffic has always been a major concern in all studies related to estimation of capacity of a highway in developing nations like India. The problem of mixed traffic is generally circumvented by making use of passenger car equivalency factors for different categories of vehicles and converting them into equivalent number of Passenger Cars Units (PCU). However, capacity is also required in terms of vehicles per hour, particularly for quick estimation of volume-to-capacity ratio on a highway. The present study investigates the effect of traffic mix on capacity of four-lane, six-lane divided highways in India. All vehicles on a highway are divided into five categories namely standard car, big car, heavy vehicle, motorized three-wheelers and motorized two-wheelers, and effect of each vehicle type on capacity of the highway is evaluated. The VISSIM software is calibrated and used to generate the traffic operations based on field data using capacity as the measure of performance. Speed-flow curves are developed to find simulated capacity values for different combinations of standard car and one of the remaining four types of vehicles in the traffic stream. The results are finally combined to propose the generalized equations to determine capacity when all or few of the five categories of vehicles are simultaneously present on a highway. [ABSTRACT FROM AUTHOR]

In recent years, road transport has become the dominant mode of surface transportation in Bangladesh, carrying more than 70% of passengers and 60% of freight. A primary concern of administrators of Bangladesh Roads & Highways Department (RHD) has moved from the construction of new roads to the management of existing road infrastructures. For this reason there is a growing need for pavement management systems and detail vehicular traffic flow information to evaluate pavements, including pavement use and the resulting deterioration. The National Highway No.1 (NH-1) is the busiest road in the country and a top development priority. An attempt is made through this research to discover the traffic composition along NH-1 as no detail traffic distribution patterns have been designed by RHD yet. Some particular outcomes includes Truck is the most predominant vehicular class with average volume of 32.29% of total traffic that indicates NH-1 is vulnerable to frequent pavement fatigue. Besides, except truck and bus (12.68%), the remaining vehicular class consist of small vehicles, which marks NH-1 very accident prone and congested highway. Though individual year varies significantly, the average growth factor of Truck and Bus is found 6.68% and 4.07% per annum respectively. [ABSTRACT FROM AUTHOR]

The majority of the roads in India are of single-lane or two-lane width. Due to budget constrains sometimes these roads are constructed with one and a half lane width (5.5 m) and is called intermediate-lane road with traffic moving on both directions. To simplify the analysis of mixed traffic on such roads, different types of vehicles are converted into equivalent number of passenger cars by using Passenger Car Unit (PCU). In the present study, an attempt is made to study the effect of the carriageway width on PCU of different vehicle categories. Data are collected at ten sections of intercity roads in different states in India. The results show that PCU value for a vehicle type varies with traffic volume and composition on the road and the carriageway width of the road being used. For example the average PCU for a big car varies from 1.46 to 1.59 on two-lane roads, 1.23 to 1.55 on intermediate roads and 1.58 on single-lane roads. All these results are discussed in this paper. [ABSTRACT FROM AUTHOR]

Sound unpleasantness due to urban road traffic at crossroads was investigated through a listening test performed in a laboratory environment. Thirty-two sound sequences were created. Four factors were studied: sound level, type of crossroads, traffic density and traffic composition. The results showed that sound unpleasantness was mainly influenced by sound level. Decreasing traffic density by a factor of 2 also reduced sound unpleasantness. The roundabout was judged less unpleasant than the crossroads with traffic lights, when traffic density was high. This outcome may be explained by differences in traffic flow dynamics between the crossroads with traffic lights and the roundabout: on the one hand, for the crossroads with traffic lights, the traffic flow resembled a constant pulsed flow, with alternate cycles of acceleration/deceleration; on the other hand, for the roundabout, the traffic flow was more similar to a constant fluid flow, with less marked cycles of acceleration/deceleration. For the roundabout only, sound unpleasantness increased with the presence of heavy vehicles (or buses). Actually, sound sequences with only light vehicles were rated less unpleasant for the roundabout than for the crossroads with traffic lights. This could be due to differences in their spectral pattern. In particular, for traffic-light scenarios, higher levels within the frequency range [400, 3000] Hz occurred when vehicles passed by, in connection with higher vehicle speeds, and higher levels in the high frequencies (around 16 kHz) occurred more often when vehicles stopped, indicating the presence of braking noise with a shrill character. [ABSTRACT FROM AUTHOR]

The California Complete Streets Act of 2008 requires local governments to update general plans so that new construction or modification of roadways considers all transportation modes, which include but are not limited to walking, cycling, and driving. This work evaluates the effect of a complete street retrofit on Ocean Park Boulevard (hereafter referred to as “the retrofit”) in Santa Monica, California, in terms of the street use by different transportation modes and corresponding ultrafine particle (UFP) and fine particle (PM 2.5 ) concentrations. After subtracting background concentrations, UFP decreased after the retrofit by 4200 particles cm −3 while PM 2.5 had no statistically significant change. The emission-weighted traffic volume, an index used to account for flows of vehicles with different pollutant-emitting capacities, decreased 26%, which may explain why UFP reductions were observed while total traffic flow remained the same. The number of pedestrians increased by 37% compared to pre-retrofit conditions and the number of cyclists remained approximately the same. Although no causality could be reached, this study observed improved air quality on street after retrofit. Nonetheless, a full evaluation of the health impacts of the retrofit requires further information about how travel behavior, not just traffic, has changed. [ABSTRACT FROM AUTHOR]

Abstract: This paper aims to estimate the effect of road pricing on the composition of traffic. By considering the case of Milan, where a charge to enter the city centre was introduced in 2008, and by relying on an unexpected and temporary suspension of the tax, we analyse the effect of the policy on flows of vehicles classified by type of engine. We have found that a road pricing scheme shifted users from Euro 0–3 vehicles (i.e., those vehicles particularly polluting according to the European Emission Standards classification and produced before 2000–2001) to liquefied petroleum gas, bi-fuel and hybrid vehicles. However, the environmental benefits of the policy were limited by a substantial increase in the usage of motorbikes. This evidence calls for a consideration of the behavioural reactions of road users when making ex ante evaluations of the social profitability of road pricing schemes. [Copyright &y& Elsevier]

Abstract: This paper formulates a continuous model of a grid road network for determining the optimal hierarchical system of road networks. The hierarchical system is represented as the proportions of area taken up by roads at each level of the hierarchy. The objective is to derive the optimal ratio of road areas that minimizes the total travel time. The model explicitly incorporates inward, outward, and through traffic as well as inner traffic to examine how traffic composition affects the optimal ratio of road areas. The result reveals that the optimal ratio of major arterial roads increases with inward, outward and through traffic. [Copyright &y& Elsevier]

Abstract: The effect of traffic composition on the noise pollution has been investigated in a small city Erzurum, located in eastern Turkey, where the population is about 400,000. Manual noise measurements and vehicle counts were performed at the four heaviest traffic points in the city for a period of 12 h. Using the information on vehicle composition and the maximum legal noise emissions of each type of vehicles, two prediction models based on genetic algorithms have been developed that can be used as tools for in-city traffic flow redesign. The models have been validated against some of the noise data. Measured traffic noise levels have been compared with predictions using the new models and some existing ones and a relatively good agreement has been obtained between them. [Copyright &y& Elsevier]

Although the rapid growth in light truck vehicle (LTV) sales, including minivans, sports utility vehicles (SUVs), and light-duty trucks, has not been associated with an overall increase in collisions or traffic deaths in the US, there is a need for a research program to determine whether particular types of collisions have become more frequent or injurious because of the increase in the percent of LTVs in traffic. This paper presents an analysis of the effect of the increasing number of LTV registrations on fatal angle collision trends in the US. The analysis investigates the number of annual fatalities that result from angle collisions as well as collision configuration (car–car, car–LTV, LTV–car, and LTV–LTV). The analysis uses the Fatality Analysis Reporting System (FARS) crash databases covering the period 1975–2000. Results showed that death rates differ based on the collision configuration. Time series modeling results showed that fatalities in angle collisions will increase in the next 10 years, and that they are affected by the expected increase in the percentage of LTVs in traffic. Forecast showed that the total number of annual deaths is expected to reach 6300 deaths by the year 2010 (an increase of 12% over 2000). Analysis into the configuration of the collision indicated the seriousness of angle collisions involving an LTV striking a common passenger car (LTV–car). A time series model illustrated the significance of time lag and percent of LTVs in traffic on the increase of this type of fatal collisions. Forecasts from the time series model indicated a 32% increase in deaths due to this type of collisions in the next 10 years. [Copyright &y& Elsevier]

Many models have been developed to evaluate the operating speeds on two-lane rural highways. However, provided information usually lacks details essential to assess their applicability at locations other than where they were developed. This paper presents a procedure to interpret raw data collected on three horizontal curve sites of different two-lane rural highway classes in Ontario. The speed observations were categorized into three vehicle classes (passenger car, light truck, and multi-axle heavy truck) and four light condition categories (day, night, and two transition periods). The minimum headway and percentile value to define the operating speed were examined, and a revision of the current practice deemed not warranted. The findings also indicated that operating speeds do not depend on the time or vehicle class. Finally, the horizontal alignment affects the operating speed, but the speeds of the two travel directions on a horizontal curve may differ even with little contribution of the vertical alignment. [ABSTRACT FROM AUTHOR]