Microsimulation study of vehicular interactions in heterogeneous traffic flow on intercity roads

Study of the basic traffic flow characteristics and comprehensive understanding of vehicular interaction are the pre-requisites for highway capacity and level of service analyses and formulation of effective traffic regulation and control measures. This is better done by modeling the system, which will enable the study of the influencing factors over a wide range. Computer simulation has emerged as an effective technique for modeling traffic flow due to its capability to account for the randomness related to traffic. This paper is concerned with application of a simulation model of heterogeneous traffic flow, named HETEROSIM, to study the relationships between traffic flow variables such as traffic volume and speed. Further, the model is also applied to quantify the vehicular interaction in terms of Passenger Car Equivalent (PCE) or Passenger Car Unit (PCU), taking a stretch of an intercity road in India as the case for the study. The results of the study, provides an insight into the complexity of the vehicular interaction in heterogeneous traffic

Randomized Clinical Trial of High-Dose Rifampicin With or Without Levofloxacin Versus Standard of Care for Pediatric Tuberculous Meningitis: The TBM-KIDS Trial

Background. Pediatric tuberculous meningitis (TBM) commonly causes death or disability. In adults, high-dose rifampicin may reduce mortality. The role of fluoroquinolones remains unclear. There have been no antimicrobial treatment trials for pediatric TBM. Methods. TBM-KIDS was a phase 2 open-label randomized trial among children with TBM in India and Malawi. Participants received isoniazid and pyrazinamide plus: (i) high-dose rifampicin (30 mg/kg) and ethambutol (R30HZE, arm 1); (ii) high-dose rifampicin and levofloxacin (R30HZL, arm 2); or (iii) standard-dose rifampicin and ethambutol (R15HZE, arm 3) for 8 weeks, followed by 10 months of standard treatment. Functional and neurocognitive outcomes were measured longitudinally using Modified Rankin Scale (MRS) and Mullen Scales of Early Learning (MSEL). Results. Of 2487 children prescreened, 79 were screened and 37 enrolled. Median age was 72 months; 49%, 43%, and 8% had stage I, II, and III disease, respectively. Grade 3 or higher adverse events occurred in 58%, 55%, and 36% of children in arms 1, 2, and 3, with 1 death (arm 1) and 6 early treatment discontinuations (4 in arm 1, 1 each in arms 2 and 3). By week 8, all children recovered to MRS score of 0 or 1. Average MSEL scores were significantly better in arm 1 than arm 3 in fine motor, receptive language, and expressive language domains (P < .01). Conclusions. In a pediatric TBM trial, functional outcomes were excellent overall. The trend toward higher frequency of adverse events but better neurocognitive outcomes in children receiving high-dose rifampicin requires confirmation in a larger trial. Clinical Trials Registration. NCT02958709

Simulation Of Highly Heterogeneous Traffic Flow Characteristics

Simulation models are mathematical/logical representations of real-world systems. Microscopic traffic simulation models have been playing an important role in traffic engineering and particularly in cases, in which field studies, involving extensive data collection, over a wide range, is difficult or expensive to conduct. As the available simulation models can only replicate homogeneous traffic flow, a model of heterogeneous traffic flow, named, HETEROSIM was developed to simulate heterogeneous traffic flow. In this model, a dynamic stochastic type discrete event simulation is adopted in which the aspects of interest are analysed numerically with the aid of a computer program. The model was validated using field observed data of traffic flow. Then, the model was applied to measure one of the fundamental charactertistics of traffic flow, namely concentration. It is a broader term encompassing both density and occupancy. Occupancy takes into account the traffic composition and speed, and hence, occupancy is more meaningful than density. The concept of occupancy can not be directly applied under heterogeneous traffic conditions, as the traffic has no lane discipline. In this paper, a new concept named, ‘area-occupancy’ is proposed to measure traffic concentration

Study of the impact of exclusive bus lane under highly heterogeneous traffic condition

The objective of this paper is to study and quantify the possible impact of provision of exclusive bus lane under heterogeneous traffic condition. The quantum of increase in level of service of bus due to introduction of exclusive bus lane was determined using a simulation model of heterogeneous traffic flow. The impact of introduction of an exclusive bus lane is measured in terms of reduction in speed of other categories of motor vehicles, due to the consequent reduction in road space, over a wide range of traffic volume. The main finding of the simulation experiment is the quantification of the maximum permissible volume to capacity ratio that will ensure a level of service of C for the traffic stream comprising all the motor vehicles, except the buses, on a typical six-lane and eight-lane divided urban roads. This study is also concerned with estimation of the probable shift of the personal vehicle users to bus due to provision of exclusive bus lanes

Planning for dedicated bus lanes on roads carrying Highly heterogeneous traffic

The desirable goal in passenger transportation is moving more people in fewer vehicles. This goal, in respect of road transport, can be attained by encouraging public transport modes like buses by assigning priority. One of the common bus priority measures is provision of reserved bus lanes on major urban roads to facilitate faster movement of buses. This paper is concerned with modification and validation of a recently developed micro simulation model of heterogeneous traffic flow and application of the model to study the impact of provision of reserved bus lanes on urban roads. The impact of introduction of an exclusive bus lane is measured in terms of reduction in speed of other categories of motor vehicles, due to the consequent reduction in road space, over a wide range of traffic volume. The main finding of the simulation experiment is the quantification of the maximum permissible volume to capacity ratio that will ensure a level of service of C for the traffic stream comprising all the motor vehicles, except the buses, on a typical eight lane divided urban road (if an exclusive bus lane is provided under highly heterogeneous traffic conditions, prevailing in Indian cities). Through this study, a framework for justification of providing exclusive bus lane has also been defined. The results of the study indicate that it is possible to introduce exclusive bus lanes on selected urban roads to enhance the level of service of bus, without much of adverse impact on the level of service of other modes of road transport under the stated roadway and traffic conditions. Provision of exclusive road space for buses, will enhance the level of service of buses and this may also result in shift of some of the personal vehicle users to buses. This study is also concerned with estimation of the probable shift of the personal vehicle users to bus due to increase in its level of service after providing exclusive bus lanes. Mode-choice probability curves to depict the probable modal shift of personal vehicle users to bus has been developed, taking the difference in travel times of the two-modes as the basis, to serve as an user friendly, ready-to-refer tool to predict the possible modal shift for a wide range of the values of the involved variables

Modelling modal shift due to the enhanced level of bus service

This study is concerned with the estimation of the probable shift of auto-rickshaw (three wheeled motorized para-transit vehicle) users to the bus due to an increase in its level of service after providing exclusive bus lanes on Indian city roads carrying heterogeneous traffic. The quantum of an increase in the level of bus service due to the introduction of an exclusive bus lane was determined using a recently developed simulation model of heterogeneous traffic flow. The data on other factors (variables) that might cause modal shift from the auto-rickshaw to the bus was collected conducting a home-interview survey based on the stated preference approach. A binary logit model of mode-choice was then calibrated using the collected data and the model was also validated using a holdout sample. A mode-choice probability curve to depict the possible shift of auto-rickshaw users to the bus is developed taking difference in the travel times of two-modes as the basis to serve as a user friendly tool to analyze the possible modal shift for a wide range of the values of the involved variables