Joint Impact of Bus Stop Location and Configuration on Intersection Performance

There are several possible bus stop locations and configurations. A bus stop can be located before or after the intersection as curb-side stop, bus bay or bus bulb. Determining the proper configuration and location of bus stop represents an important planning decision. While previous research efforts in literature have suggested some advantages and disadvantages regarding bus stop locations and configurations, little effort has been made towards understanding the joint impact of bus stop location and configuration on the transit and other vehicle traffic performance on the intersection. So, this paper analyses the joint impact of bus stop location and configuration on the operational characteristics of traffic flow in terms of average bus trip time and control delay. These operational performance measures for various intersection layouts, volume distributions, movement splits, average bus dwell times and bus departure frequencies have been obtained using calibrated microsimulation traffic software.</p

Determination of Applicable Adjacent Horizontal Curve Radii Using Operating Speed

Design of curves and their adjacent elements presents the greatest safety problem on rural two-lane roads. The use of the existing alignment consistency safety criteria (design, operating speed, and driving dynamic consistency) could have some shortcomings, especially in countries where the project or design speed is in use instead of (higher) operating speed. The consequence is that the designer should use smaller cross fall on curves than needed, while the calculated side friction is lower than in reality. Further, the existing graphs of adjacent curve radii do not take into account that there is a maximum operating speed achieved for a certain radius or long tangent above which it does not increase. This paper presents a methodology for determination of adjacent horizontal curve radii, with and without tangent between, based on the operating speed models which include dependence of operating speeds on tangents and curves on speed of adjacent alignment elements as well as maximum tangent and curve speed. The developed graphs of adjacent radii at the same time include the limiting values of driving dynamic consistency criteria, so the road designer does not need to calculate permissible and demand side friction for every combination of adjacent alignment elements.</p

Use of simulation models in traffic analysis

Opisan je metodološki pristup pri izradi prometne analize utjecaja planiranih zahvata u prostoru na odvijanje prometa u neposrednom okruženju. Prikazane su osnovne karakteristike simulacijskih modela kojima se procjenjuje kvaliteta odvijanja prometnih tokova. Dan je primjer prometne analize gospodarske zone Podi-zapad primjenom navedene metodologije, uz upotrebu simulacijskog modela CORSIM koji omogućuje određivanje kritičnih lokacija i usporedbu mogućih varijantnih rješenja.The methodological approach used in traffic analysis, and aimed at determining the influence of planned developments on the operation of traffic in the immediate vicinity of such developments, is described. Principal properties of simulation models used for estimating quality of traffic flow are presented. An example of traffic analysis conducted according to the above mentioned methodology, and involving the use of CORSIM simulation model for determining critical locations and comparing possible alternatives, is presented for the economic zone of Podi-West

IMPACT OF ROAD ALIGNMENT ON FUEL CONSUMPTION AND GAS EMISSIONS – EXPERIMENTAL AND ANALYTICAL RESEARCH

This research analysed the impact of road alignment on the fuel consumption and gas emissions of a vehicle driven at a free-flow speed by an 85th percentile driver. The field experiment included constant and free-flow speed rides by a personal car equipped with a high-performance (10 Hz) Bluetooth global position device and on-board diagnostics connector, with which the travel path, speed, acceleration, and consumption data were recorded. Regression analyses of the dependence of free-flow speed and fuel consumption on the geometric characteristics of the road (curvature, length, longitudinal slope, etc.) resulted in the formation of a reliable model that could compare alternative road designs for a given corridor in terms of route economy and safety. The main parameters contributing to the consumption on tangents were the slope and radii of adjacent curves. For constant speed, the slope was the only geometric parameter that had an impact on fuel consumption

Estimation of Critical Headway at Small Urban Roundabout

Before choosing an intersection project design, an important step is to examine the justification of the construction on the basis of defined criteria. One of the key criteria is the analysis of capacity. Large numbers of roundabout capacity models are present in the world, most of them adapted to the conditions of the country they originate from and they need to be calibrated for local conditions. Key parameters for calibration are critical headway and follow-up headway. Follow-up headway can be measured directly in the field, while critical headway cannot be measured, but is estimated. Many critical headway estimation methods exist (over 30) and each of them provides different values. Different values of critical headway result in different capacity estimation values. This raises the question which method provides more realistic estimations under certain conditions. In this paper, four most frequently used critical headway estimation methods (Raff, Maximum likelihood method, Wu, Logit) were selected to be tested by comparison of theoretical capacity models and actual measured capacity at a small urban roundabout.</p

Operating speed models of two-lane rural state roads developed on continuous speed data

Ovaj rad prikazuje modele za predviđanje operativne brzine na pravcima i krivinama dvotračnih vangradskih cesta razvijene na kontinuiranim podacima o brzinama vožnje. Podaci se odnose na 20 vozača koji su vozili svoja vozila duž 18 km duge dionice dvotračne državne ceste. Podaci su prvo korišteni za određivanje minimalne operativne brzine u krivinama i maksimalne operativne brzine na pravcima te njihovu usporedbu s brzinama, u sredini krivina i pravaca, koje se najčešće koriste za razvoj modela operativnih brzina. Nema značajne razlike između modela brzina razvijenih na temelju podataka o brzinama na sredini pravaca i krivina i modela razvijenih na temelju podataka o maksimalnim i minimalnim operativnim brzinama na pravcima, odnosno krivinama. Modeli razvijeni na temelju kontinuiranih podataka imaju veći koeficijent determinacije od modela razvijenih na temelju točkastih podataka o brzinama u sredini pravaca i krivina. Stoga se može zaključiti da metoda mjerenja ima značajniji utjecaj na kvalitetu modela brzina od mjesta mjerenja.This paper presents models for predicting operating speeds on tangent sections and curves of two-lane rural roads developed on continuous speed data. The data corresponds to 20 drivers of different ages and driving experiences, driving their own cars along an 18 km long section of a state road. The data were first used for determination of minimum operating speeds on curves and maximum operating speeds on tangents and their comparison with speeds in the middle of curves and tangents i.e. speed data used in most of the operating speed studies. There was no significant difference between speed models developed using speed data in the middle of tangents and curves and models developed using maximum and minimum operating speeds on tangents and curves. Models developed on continuous data have higher coefficient of determination than models developed on spot speed data. It can be concluded that the method of measuring has more significant impact on the quality of speed model than the location of measurement

Detection and analysis of hazardous locations on roads: a case study of the Croatian motorway A1

The present paper describes research undertaken to identify causes underlying single-vehicle accidents (in terms of road design, driver behaviour and vehicle handling characteristics), which continuously happen in one specific section of Croatian motorway A1. The research resulted in a proposed procedure for a detection of hazardous locations on motorways and analysis of possible causes of single-vehicle accidents. The main part of the procedure involves test-rides with a vehicle equipped with devices (a ball bank indicator and a GPS data logger), which collect data on driver’s behaviour and vehicle handling characteristics (position, speed, longitudinal and lateral acceleration, heading, path radius, etc.). Despite the fact that the motorway was designed in accordance with the design guidelines, test rides performed by higher operating speeds identified two locations with a lateral acceleration change a few times higher than the design value. The collected data are then used for analysing hypotheses about the possible causes of accidents by using a vehicle dynamic model. The hypothesis that a sudden change in lateral acceleration could result in a driver’s inadequate manoeuvre like braking and cause a vehicle accident was analysed with a transient bicycle model. The results of test rides and the transient bicycle model indicate that speed, intensity of deceleration and underinflated tires significantly affect the probability of a single-vehicle accident. First published online 31 January 201

DEPENDENCE OF CARRIAGEWAY CROSSFALL ON OPERATING SPEED

This paper describes a rational approach to improve the existing guidelines for road design in the regions of Slovenia, Croatia, Bosnia and Herzegovina, and Serbia in order to determine the carriageway crossfall in curves. In these guidelines there are certain shortcomings in determination of crosfall in comparison to some other European countries guidelines. During the last decades, worldwide and in Europe specifically, significant studies have been conducted on the issue of the operating speed and its implementation into the design process. Most European countries have been implementing this concept. The new German guidelines went a step further and introduced a new concept of a self-explaining class road. Using the results of research carried out in Croatia, this work focuses only on a determination of the carriageway crossfall based on operating speed, separately observing new and existing roads. Whereas the new road segments require implementing the principle of a consistent route, an existing road network can be safely improved only by introducing the criteria of the determination of crossfall in curves based on the operating speed

Sight distance at at-grade intersections

Obrađuje se problematika preglednosti na cestovnim raskrižjima u razini. Na raskrižjima su naglašeni problemi sigurnosti prometa, pri čemu je preglednost jedan od najvažnijih zahtjeva za dobar projekt raskrižja. U članku su opisani utjecaji na preglednost raskrižja i načini određivanja potrebne preglednosti koji se primjenjuju u RH i SAD-u. Uspoređeni su propisi pri čemu su istaknuti nedostaci hrvatskih propisa u pogledu potrebne preglednosti za manevre skretanja u glavni tok.The issue of sight distance at at-grade road intersections is analyzed. Traffic safety problems are quite pronounced at road intersections, and the sight distance is considered as one of the most important requirements for definition of a good-quality intersection design. Various influences on sight distance at road intersections are described, and methods used in Croatia and the USA to define the necessary sight distance are presented. Relevant regulations are compared, and shortcomings of Croatian regulations, namely sight distance for turning manoeuvre to access the main flow of traffic, are presented

Modelling Free Flow Speed on Two-Lane Rural Highways in Bosnia and Herzegovina

Free flow speed is used as a parameter in transportation planning and capacity analysis models, as well as speed-flow diagrams. Many of these models suggest estimating free flow speed according to measurements from similar highways, which is not a practical method for use in B&H. This paper first discusses problems with using these methodologies in conditions prevailing in B&H and then presents a free flow speed evaluation model developed from a comprehensive field survey conducted on nine homogeneous sections of state and regional roads