TRAFFIC ENGINEERING

Traffic engineering pertains to the analysis of the behavior of traffic and to design the facilities for the smooth, safe and economical operation of traffic. Understanding traffic behavior requires a thorough knowledge of traffic stream parameters and their mutual relationships. In this chapter the basic concepts of traffic flow is presented.

is studied before and after some change in road conditions, and statistical technique is used to find out whether the change significantly reduces journey times or accidents. Extensive researches on similar lines are carried out in the U.S.A., notably by the Division of Highway Transport Research, and by certain university departments such as the Post-graduate School of Highway Engineering at Yale.

Jurnal Teknologi, 2015

Average travelling speed usually applied in the traffic analysis as required in the fundamental traffic model. As one type of speed under the space-mean speed, most of the researchers have derived the equation to estimate the space-mean speed. There are a few factors that influence the speed changes along the segment. The fluctuate speed along the segment give an idea to average the spot mean speed from at least two points in order to estimate the space-mean speed. This paper explores an alternative method on how to convert the time-mean speed to space-mean speed that can represent the actual operating speed along segment using the average technique. A total of 18 data sets of time-mean speed and space-mean speed in six segments of uninterrupted two-lane single carriageway road were collected using automatic traffic counter and moving car observer, respectively. Two sets of automatic traffic counter were installed along the segment to record the spot speed and then converted to the ...

Highway Research Journal, 2017

Collection of Space Mean Speed (SMS) data, which finds application in many traffic engineering problems, is tedious and cost ineffective in countries like India where automatic speed detection systems are not in vogue. In view of this issue, it was decided to express space mean speed as a function of a relatively conveniently measurable mean speed measure i.e. Time Mean Speed (TMS). Review of the already developed statistical models by using data collected under this study indicated that those models in their present form are not applicable for heterogeneous traffic conditions which are prevalent on Indian roads. Therefore, in this paper, appropriate modifications to the existing SMS models were effected using data collected on multilane divided National Highways in the National Capital Region of India.

Probabilistic models describing macroscopic traffic flow have proven useful both in practice and in theory. In theoretical investigations of wide-scatter in flow-density data, the statistical features of flow density relations have played a central role. In real-time estimation and traffic forecasting applications, probabilistic extensions of macroscopic relations are widely used. However, how to obtain such relations, in a manner that results in physically reasonable behavior has not been addressed. This paper presents the derivation of probabilistic macroscopic traffic flow relations from Newell's simplified car-following model. The probabilistic nature of the model allows for investigating the impact of driver heterogeneity on macroscopic relations of traffic flow. The physical features of the model are verified analytically and shown to produce behavior which is consistent with well-established traffic flow principles. An empirical investigation is carried out using trajectory data from the New Generation SIMulation (NGSIM) program and the model's ability to reproduce real-world traffic data is validated.

DESCRIPTION Collection of Space Mean Speed (SMS) data, which finds application in many traffic engineering problems, is tedious and cost ineffective in countries like India where automatic speed detection systems are not in vogue. In view of this issue, it was decided to express space mean speed as a function of a relatively conveniently measurable mean speed measure i.e. Time Mean Speed (TMS). Review of the already developed statistical models by using data collected under this study indicated that those models in their present form are not applicable for heterogeneous traffic conditions which are prevalent on Indian roads. Therefore, in this paper, appropriate modifications to the existing SMS models were effected using data collected on multilane divided National Highways in the National Capital Region of India.

2004

In this work we had to face the topic of intrinsic road safety experimentally by investigating two interurban roads. These roads are characterised by different types of traffic. The results of the investigation are given in the form of prediction relations with their relevant speed diagrams. The present investigation, to be carried out in the field, intends to verify, on some sections considered as significant, the relationship and mutual incidence between the variables flow, road geometry and speed. In the processing of the results, use will also be made of specific instruments for evaluating the geometrical consistency of the road alignment in accordance with operating speed. Our experimental investigation aimed at studying operating speeds on two different categories of roads as regards both importance and circulation. First of all we selected the road samples which belong to the A18 Messina-Catania motorway and to the SS 626 Licata-Ravanusa state highway. The study contemplated the use of a laser beam speedometer and some digital camcorders. In each section we considered two cross-sections at the same time, one on a tangent and one on a curve. At the same time, we also measured traffic flows which were subsequently disaggregated according to all the calculation parameters necessary to establish the level of service. In order to have a clearer interpretation of the experimental evidence and to propose some prediction relations we analysed the rapport between V 85 and some geometrical parameters like CCR s , CCR, i s and i. Both prediction relations and their determination coefficients show that it is the simultaneous and synergic action of planimetric and altimetric elements that determines a high degree of correlation to V 85. In both road samples we found that operating speed values are almost always higher than the design speed of the geometrical elements considered. On the other hand, a general increase in operating speed involves very small speed variations in the transition from one element to the other. This leads us to think that the layouts are appreciably consistent, as can be seen from the diagrams prepared on the basis of the prediction reports V 85-CCR s-i s. As for the motorway sections studied, this datum conflicts with what the curvature planimetric-design speed diagrams, prepared on the basis of the present Italian geometric design standard, affirm. We think that these prediction relations could become behavioural models, on the basis of more thorough studies, referring to a specific category of road geometry characterised by a specific mobility function. Moreover, the values of the evaluation parameters of the consistency of the road should vary-although the intervals should always be small-in relation to both the geometrical and functional characteristics of the road.

Transport, 2020

Fundamental diagram, a graphical representation of the relationship among traffic flow, speed, and density, has been the foundation of traffic flow theory and transportation engineering for many years. Underlying a fundamental diagram is the relation between traffic speed and density, which serves as the basis to understand system dynamics. Empirical observations of the traffic speed versus traffic density show a wide-scattering of traffic speeds over a certain level of density, which would form a speed distribution over a certain level of density. The main aim of the current research is to study on the distribution of traffic speed in different traffic conditions in the urban roads since the distribution of traffic speed is necessary for many traffic engineering applications including generating traffic in micro-simulation systems. To do so, the traffic stream is videotaped at various locations in the city of Budapest (Hungary). The recorded videos were analysed by traffic engineer...

Speed analysis on urban roads sections start from need tied up to traffic assignment models in urban networks: to calculate the average running time in a road section it is necessary to have a good evaluation of average running speed for that road section. First experimentations for the study of drivers «realized» speed (for rural roads) have been published already in 1988. In 1997 it has been published a first expression for «realized» speed in function of curvature (1/R) and of absolute value of the longitudinal road gradient for some typologies of common rural roads.

The information of diverse plainly visible parameters of traffic volume count is a critical fundamental input required for arranging, examination and operation of roadway frameworks. Communicating activity volume as number of vehicles passing a given segment of street or activity path per unit time will be improper when a few sorts of vehicles with broadly shifting inactive and energetic characteristics are comprised within the activity. The issue of measuring volume of such heterogeneous activity has been tended to by changing over the diverse sorts of vehicles into proportionate traveler cars and communicating the volume in terms of PCU (Traveler Car Unit) per hour, spot speed ponders and immersion stream. The vehicles of profoundly heterogeneous activity with broadly shifting physical and operational characteristics such as the one winning on Indian streets, possess based on the accessibility of space, any helpful horizontal position on the street without any path teach. The interaction between moving vehicles beneath such heterogeneous activity condition is profoundly complex.