Passenger Car Unit Estimation Research Articles

Non-Linear Evaluation Model to Analyze Saturation Flow under Weak-Lane-Disciplined Mixed Traffic Stream

Saturation flow is an essential parameter for the performance evaluation and signal cycle design of an intersection. However, in a weak-lane-disciplined mixed traffic stream, vehicles (mainly motorized two- and three-wheelers) are more interested in forming queues with the behavior of creeping and infiltration through the larger vehicles for a quick dispersion. Consequently, a high rate of discharge can be found in the first few seconds of green, followed by a wavering discharge pattern to the end of the green period. In this context, the present study frames a non-linear evolutionary model (NLEM) to analyze passenger car unit (PCU) and saturation flow value by minimizing the vehicle encroachment and wavering in discharge for mixed traffic stream. Field traffic data was collected from 10 signalized intersections from three different cities of India. The NLEM considers the vehicle discharge during the saturated green interval in the optimization process to analyze PCU and saturation flow value. The result indicates an appropriate estimation of PCU and saturation flow concerning the Highway Capacity Manual. The discharge profile obtained using the proposed model also specifies the model’s aptness in analyzing the effect of vehicle encroachment and wavering throughout the green period. Thus, the proposed NLEM is probably suitable for analyzing the PCU and saturation flow of an intersection where vehicle interaction is sensitive because of a mixed scenario.

Estimation of Passenger Car Unit for Undivided Two-Lane Roads in the Mountainous Region

Indian traffic conditions consist of diverse vehicle categories of different static and dynamic properties, making it a heterogeneous flow. The vehicles' complex and dynamic behaviour can be dealt with by converting them into an equivalent passenger car unit (PCU). This study estimates the dynamic PCU values of vehicles in mixed flow conditions for undivided two-lane mountainous roads in India using the speed-area method. The vehicular dimensions and their operating speeds were considered as the prime factors for PCU estimation. The data collected from the sites located in the mountainous region of Himachal Pradesh was used to calculate the PCU value for different vehicles. When compared to the values provided in the Indian Highway Capacity Manual 2017, the PCU value of some vehicle categories was found to be different from the suggested range in the HCM. A variation in the PCU value was observed at different traffic flow, vehicular composition, and V/C ratio. This dependency of PCU values with these three parameters was analysed, and based on that, a set of mathematical models were developed. These models were further validated by statistical analysis with data collected at another study site with similar characteristics. As Indo-HCM 2017 suggests PCU values for plain terrain; these models can help forecast the vehicles' PCU values in the mountainous regions.

Estimation of Passenger Car Unit on urban roads: A literature review

• This paper provides an idea of the status of PCU related research. • It also extends a collective knowledge of how PCU varies with the change in traffic and other conditions. • The present paper helps the reader to adopt a suitable PCU estimation method based on some prevailing factors. 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.

Effect of PCU Estimation Methods on Capacity of Two-Lane Rural Roads in India: A Case Study

The majority of roads in India are two-lane undivided in nature with a supreme heterogeneity in traffic composition. As there is a large variation in dynamic profile of each vehicle, a single unit is essential to estimate the roadway capacity. The Passenger Car Unit (PCU) values of different vehicle categories have significant impact on the estimated roadway capacity. To study this effect, Kolkata-Basanti highway and Howrah-Amta Road, two state highways in the eastern part of India having two lanes each, were selected. Kolkata-Basanti highway connects the rural regions of Sundarban with Kolkata whereas Howrah-Amta Road connects the Amta region with Kona Expressway in the district of Howrah. It has a considerable heterogeneity in traffic with large speed differentials among the vehicles. Greenshield’s linear model is applied to estimate the Capacity where the PCU values are determined by three different methods. These include the static PCU value from IRC 64 (1990), the concept of Dynamic PCU values as proposed by S. Chandra (2004) and the method suggested in Indo-HCM (2017). The analysis shows that there is a significant difference in the roadway capacity estimated using static PCU values from the other two methods. This may be attributed to the fact that the dynamism of the vehicles in the PCU value determination is not considered in the static PCU values listed in IRC 64 (1990).

An advanced approach for estimation of PCU values on undivided urban roads under heterogeneous traffic conditions

ABSTRACTMajority 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.

An Approach to Deal with Heterogeneity on Roundabouts

Sufficient literature is available on approaches to deal with heterogeneous traffic on mid-blocks in developing countries, but not much work is done on roundabouts. The estimation of passenger car unit (PCU) for different vehicles to convert heterogeneous traffic into homogeneous traffic is a well-accepted procedure. But the parameters used for mid-blocks may not be helpful on roundabouts as traffic flow characteristics on the two locations are different. Suggested PCU values on roundabouts from developing countries are not recent, and needs a relook. It is also not clear whether to use static or dynamic PCU values on account of possible temporal and spatial variations across locations. This paper presents an estimation approach for PCUs on roundabouts and suggests using static value instead of dynamic. The problem to deal with re-estimation of PCU values at different locations, due to possible traffic flow variations, is dealt with by proposing a heterogeneity equivalency factor (H-Factor). The factor is multiplicative and converts heterogeneous traffic (veh/h) into homogeneous traffic (pcu/h).

Estimation of passenger car unit for heterogeneous traffic stream of urban arterials: case study of Kolkata

Rapid urbanization increases the number of vehicles on a road section significantly throughout the country. Traffic in India is generally heterogeneous consisting of variety of vehicles which comprise wide range of static and dynamic characteristics. To estimate volume of such heterogeneous traffic it is essential to convert the different types of vehicles into equivalent passenger cars and express the volume in terms of Passenger Car Unit (PCU) per hour. The equivalency unit is universally adopted for measurement of traffic volume and the value is obtained by taking the passenger car as the ‘Standard Vehicle.’ The present study has been concentrated on four and six lane divided urban arterials in Kolkata. The PCU of vehicles have been presented for both categories of urban roads and the values are found to be higher than the values given in IRC: 106-1990. It has also been observed that, PCU values of different types of vehicles have been found to be different for different ranges of volume, composition and v/c ratio. Mathematical relationships have been developed on the basis of the variation of PCU with traffic stream parameters. The relationships are developed to forecast the PCU for several vehicular categories that have been statistically validated for different ranges of traffic stream parameters.

Passenger Car Unit Estimation at Signalized Intersection for Non-lane Based Mixed Traffic Using Microscopic Simulation Model

In India, traffic on roads is mixed in nature with widely varying static and dynamic characteristics of vehicles. At intersections, vehicles do not follow ordered queue and lane discipline. Different vehicle types occupy different spaces on the road, move at different speeds, and start at different accelerations. The problem of measuring volume of such mixed traffic has been addressed by converting different vehicles categories into equivalent passenger cars and expressing the volume in terms of Passenger Car Unit (PCU) per hour. The accurate estimation of PCU values for different roadway and traffic conditions is essential for better operation and management of roadway facilities. Hence, the objective of the present study is to estimate the PCU values at signalized intersection in mixed traffic and to study the influence of traffic volume, traffic composition and road width on PCU values.For this purpose, a mixed traffic simulation model developed specifically for a signalized intersection was used. The model was calibrated and validated with the traffic data collected from a signalized intersection in Chennai city. Simulation runs were carried out for various combinations of vehicular composition, volume levels and road width. It was observed that presence of heavy vehicles and increase in road width affects the PCU values. The obtained PCU values were statistically checked for accuracy and proven to be satisfied. The PCU values obtained in this study can be used as a guideline for the traffic engineers and practitioners in the design and analysis of signalized intersections where mixed traffic conditions exist.

Three methods of PCU estimation at unsignalized intersections

Estimation of passenger car unit (PCU) is a vital component of any traffic study conducted in developing countries owing to the heterogeneity in the vehicular traffic. Past studies on PCU factors are majorly limited to intercity and urban roads. However, PCU factors for different types of vehicles on unsignalized intersections have not been investigated so well. This paper presents three methods of estimating PCU factors for different types of vehicles on unsignalized intersections under highly heterogeneous traffic conditions. The first method is based on the occupancy time of a vehicle while clearing the intersection. The second method is based on the capacity of a priority movement estimated in terms of different vehicle categories. Queue clearance rate is used as the basis for PCU estimation in the third method. Data were collected at two unsignalized intersection in semi-urban area of two cities of India and PCU for different types of vehicles is determined using the three methods. The resulting values of PCU factors were found to be logical and are representatives of the actual field conditions.