This study proposes a bi-level optimization model for the transit frequency setting problem in bi-modal networks. The objective of the upper-level problem is to obtain a solution set of bus line frequencies that provide the minimum total travel cost of the car and bus users. Differential Evolution (DE) algorithm is employed in the upper-level model to determine the optimal headways for a given route structure. The lower-level model is a congested multi-modal user equilibrium assignment model, which considers the interactions of car and bus flows, for determining joint mode/route preferences of the network users, which considers the interactions of car and bus flows. The developed model is tested on Mandl’s benchmark network to evaluate its performance and applicability. The comparative experiments demonstrate that the proposed model leads to reductions in transportation costs. Also, the results of numerous optimization runs show that DE performs well in finding similar frequency sets in independent optimizations.
Pedestrian traffic has less priority than vehicle traffic in Turkey’s transportation system. In recent years, there has been a growing interest in understanding pedestrians’ behavior. This paper investigates high school students’ (15-18 age range) gap acceptance behavior at unsignalized midblock crossings by designing a before and after study. The midblock crossing is conventional in the first situation. But after, the midblock crossing is raised. This paper aims to find the effect of raised midblock crossing on pedestrians’ acceptable gap behavior. In this study, a midblock crossing near a high school in Izmir City was chosen. Data was gathered by using two video cameras in the morning (7.00-8.00 AM). The obtained data were extracted from the footage. The data were analyzed by performing two-way and one-way analysis of variance (ANOVA). The legal crossing rate of the students increased with the installation of the raised midblock crossing. Also, average vehicle speed and 85th percentile speed determined for both situations. Thus, the number of acceptable gaps increased as well as the waiting time decreased significantly.
In this study, an optimization model for road maintenance scheduling is proposed. The proposed model determines a maintenance schedule for a given set of links in an urban road network, that
minimizes the total travel time during the maintenance period under a set of assumptions and a particular crew number constraint. It is assumed that all lanes of a road to be repaired are closed to traffic during the maintenance. Ant Colony Optimization (ACO), a suitable algorithm for discrete transportation problems, is employed in the proposed model. The model generates a set
of roads to be closed for each maintenance day. The total travel time during the whole maintenance period is calculated using the deterministic user equilibrium assignment model. The
proposed model is applied to a test network, and more efficient schedules in terms of total travel time are obtained compared to randomly generated schedules.
Over the last few decades, rapidly growing cities in terms of population and land use have led to many transportation-based problems such as longer travel times, traffic congestion, traffic crashes, and air and noise pollution. Increasing the modal share of transit systems appears to be one of the most effective methods to solve transportation-based problems. However, transit systems, particularly in countries having limited resources, should be used efficiently to achieve sustainable urban mobility. Even only adjusting frequencies of transit lines, with no infrastructure investment cost requirements, can provide a more efficient transit system. In this paper, a transit frequency setting model based on the Firefly Algorithm (FA), which is a relatively new metaheuristic, for the transportation network design problems is presented to minimize total user cost under a fleet size constraint. The proposed model is performed on a 10-route Mandl’s Test Network using different combinations of parameters to demonstrate the effect of parameter values on the solution quality. After that, the best solution of 30 solutions obtained by the calibrated parameter values is compared to the existing frequency set of the 10-route transit network. The results show that the FA can obtain better frequency sets by selecting the proper values for the parameters.
Public transportation vehicles, with their confined spaces and limited ventilation, are considered among the primary factors in the spread of COVID-19. As a measure to slow the spread of the virus during the pandemic, governments have applied passenger capacity restrictions to ensure physical distancing. On the other hand, the increase in the risk of disease transmission associated with passengers waiting together at stops is omitted. In this study, we consider the risk of disease transmission as a travel cost and formulate a risk minimization problem as a transit network frequency setting problem. We develop a bi-level optimization model minimizing the total infection risk occurring at stops, namely, the cumulative disease transmission risk cost. The Differential Evolution algorithm is employed to cope with the NP-hard bi-level transportation network design problem. We propose a novel objective function for the upper-level model, considering the infection risk cost based on passenger traffic at public transportation stops. A congested user-equilibrium transit assignment model is utilized to determine passenger movement. The proposed model is applied to a small-size hypothetical network, and a mid-size test network. Experimental studies provide evidence that the model can produce optimal solutions. Optimization results show significant improvements in the reduction of disease transmission risk compared to the optimizations depending on the traditional practice of transportation network planning based on user and operator costs. The proposed model provides risk cost reductions of 51% and 22% compared to the optimal solutions based on user cost minimization in the hypothetical network and Mandl’s network, respectively.
Trafik bir bütün olarak değerlendirildiğinde yayaların önemli bir etmen olduğu açıktır. Geçmişte yaya davranışları çok az çalışmada incelenmiş olsa da son dönemde farklı ülkelerde yürütülen çalışmalar sayesinde yayalarla ilgili detaylı bilgi toplanılmaya başlanmıştır. Çalışmalar genellikle ışıklı yaya geçitlerinde yürütülmüş olup üst geçit bölgelerini kapsayan çalışmalar sınırlı sayıdadır. Çalışma kapsamında yürüyen merdivenin üst geçit kullanımına etkisini belirlemek adına İzmir’de benzer yol geometrisine sahip iki adet üst geçit bölgesi belirlenmiştir. İki üst geçit bölgesinde de yayanın yol seviyesinde geçişini engelleyecek fiziksel engel bulunmamaktadır. Ayrıca aynı üst geçit bölgesinde yayalara kısa bir anket uygulanarak, kullanmış oldukları yaya üst geçidine ait güvenlik algılarının ortaya çıkarılması ve yaptıkları geçiş hakkındaki bireysel değerlendirmelerinin öğrenilmesi amaçlanmıştır. Üst geçit kullanan yayaların geçiş süreleri ile kural dışı geçiş yapan yayaların geçiş süreleri belirlenerek üst geçit tutarlılık oranı belirlenmiştir. Yürüyen merdiven bulunan ve bulunmayan üst geçit bölgeleri için tutarlılık oranı bağıntısının geçerliliği değerlendirilmiştir. Bağıntının sadece zaman parametresini dikkate alması nedeniyle farklı özellikteki üst geçitler için gözden geçirilmesi önerilmiştir. Toplanan veriler değerlendirildiğinde yürüyen merdiven bulunmayan üst geçit bölgesinde ortalama karşıdan karşıya geçme hızı 1.72 m/s, yürüyen merdiven olan üst geçit bölgesinde ise 1.63 m/s olarak bulunmuştur.
Most of the studies related to pedestrian behavior focus on signalized intersections while a few focus on overpasses. In this study pedestrians’ behaviors at overpass locations are investigated. For this purpose, two overpass locations were selected and pedestrians either using the overpass or crossing illegally were recorded by video cameras and 2713 accepted/rejected time gaps were measured. Raff’s method (deterministic approach) is used to estimate the critical gap. The collected data were then evaluated by a binary logit model (probabilistic approach) to estimate time gaps. The selected overpasses were observed on weekdays continuously for six hours. At the overpass locations 656 illegal crossings were observed on weekdays continuously for six hours. Safety margin of 377 pedestrians were evaluated by ANOVA analysis to identify the significant factors. ANOVA results revealed that interactions of gender, age, and vehicle position, items carrying, group size had significant effects on safety margin.
Weaving is defined as the crossing of two or more traffic streams traveling in the same general direction along a significant length of the roadway without the aid of traffic control devices. Weaving segments are formed when a merge area is closely followed by a diverge area, or when a one-lane on-ramp is closely followed by a one-lane off-ramp and the two are joined by an auxiliary lane. Highway Capacity Manual 2010 proposed a methodology to estimate the level of service at weaving segments. This methodology is adopted for the present study and applied to two weaving segments in Izmir, Turkey. The purpose of this study is to identify the level of service at weaving segments.
This study proposes a bi-level optimization model for the transit frequency setting problem. A relatively new meta-heuristic algorithm, firefly algorithm is employed in upper-level to determine optimal headways for a given route structure to minimize operator cost. The approach adopted to achieve the objective is to ensure efficient use of vehicles by obtaining maximum occupancy rate. Frequency-based transit assignment is done using PTV VISUM software package in lower-level in order to determine flows resulting from headway set generated in upper-level. Tests are performed on Mandl’s network and transit network of Karaman, Turkey to evaluate the performance and applicability of the proposed model, obtained results are presented, and some conclusions are drawn.
Transportation planning is an important factor in terms of urban development. An effective transport system is a major component of social and economic development in urban areas. Public transport accessibility in cities is also an important point in this sense. Public Transport Accessibility Level (PTAL) is a method that measures the accessibility of public transport in a regional and urban area. The purpose of this study is to examine the impact of accessibility of public transport systems on different routes. This impact was investigated by the PTAL method. The accessibility of the tramway line within the province of Karsiyaka district of Izmir City was investigated along with the proposed route. Firstly, the existing route accessibility was calculated. Then, the accessibility of the proposed route was calculated. Both cases are compared.
From the beginning of the 20th century, developments in science and technology and the increase in population have brought rapid and uncontrolled urbanization. An automobile and city relation comes at the beginning of transportation problems. Parking problems are the least considered transportation problems.
In this study, it is aimed to shed light on the car park choice behavior in Izmir. Selected multi story and on-street car parks in Izmir Alsancak region have been examined. The factors affecting the preferences of those who use these car parks have been examined. Data was collected with the help of surveys given in the scope of the study. The drivers were asked about their socio-economic characteristics, travel information and car parks. The obtained data were modeled by the logit model.
At the end of the study, variables affecting parking choice were determined. These variables were gender, purpose of the trip, travel time and walking distance to final destination. The effects of the variables in the study were tried to be explained. According to the obtained results from the surveys and logit models, solution proposals are given related to parking problems in the observed areas.
The aim of designing overpasses is to provide safe road crossings for pedestrians by helping them to avoid conflicts with motor vehicles. However, the number of pedestrians who do not use overpasses to cross the road is very high. An observational survey of illegal road crossings was conducted at four overpass locations in Izmir, Turkey to determine the crossing time, crossing speed of the pedestrians and their distance and time gap perception for safe road-crossing within 25 m of the overpasses in both directions. Crossing time is the time needed for a pedestrian to cross a particular road. Time gap is strongly related with safety margin. If a pedestrian chooses a larger time gap, then the arrival time of the oncoming vehicle to the crossing point of the pedestrian increases thus, the possibility of a collision decreases. Each overpass was observed on weekdays during peak afternoon (12.30-13.30) and evening hours (17.00-18.00). At all overpass locations 454 illegal crossings were observed. ANOVA results revealed that age had a significant effect both on safety margin and crossing time. During the observations a survey was conducted among pedestrians who completed their crossings either using the overpass or at street level within 25 m of the overpass (n=231). Factors affecting the crossing choice of pedestrians were specified in the surveys. The major part of the respondents (71.7%) indicated that time saving was the main reason for crossing at street level. Pedestrians’ crossing speeds were extracted from the video recordings to observe the effect of speed limit on pedestrian behavior. As a result, at locations where the speed limit was 70 km/h, pedestrians’ average crossing speed was found to be 1.60 m/s and 1.73 m/s while at locations where the speed limit was 50 km/h, pedestrians’ average crossing speed was found to be 1.04 m/s and 0.97 m/s. This shows that pedestrians feel safer while crossing when the vehicle speed is low.
Purpose of designing crosswalks is to allow pedestrians to cross the roads safely avoiding conflicts between pedestrians and motorized vehicles. However, pedestrians do not always comply with the crossing rules, whether it is timing (signalization) and/or location (crossing facility). An observation survey of illegal crossings was conducted at six intersections in Izmir, Turkey to determine the distance and time gap perception of the pedestrians for safe road-crossing within the 25 m of the crosswalk. Each intersection was observed on weekdays during afternoon (12.30–13.30) and evening peak hours (17.00–18.00). Totally, 444 illegal crossings were observed at all intersections. Data were analyzed playing the video recordings in office. All roads were consisted of two lanes. In this study pedestrians’ illegal crossing behavior at signalized intersections depending on the position of the oncoming vehicle is of interest. Safety margins and crossing times of the pedestrians were also reported. Position of the vehicle was determined for the first lane at the instant the pedestrian stepped the lane. Pedestrians’ distance gap perception was categorized into five groups depending on the position of the oncoming vehicle which are; vehicle is within the 25 m of the crosswalk, vehicle is within the 25–50 m of the crosswalk, vehicle is within the 50–75 m of the crosswalk, vehicle is just beyond 75 m, and vehicle is out of field of view. Factors affecting the distance gaps, safety margins and crossing times were analyzed by ANOVA. The most significant effect was the vehicle speed in all analysis. Pedestrians based their decision of crossing on distance rather than time gap.
Young drivers’ high traffic violation involvement rate and significant contribution to traffic crashes compared to older drivers creates the need for detailed analyses of factors affecting young drivers’ behaviors. This study is based on survey data collected from 2,057 18-29 year old young adults. Data were collected via face-to-face questionnaire surveys in four different cities in Turkey. The main objective of this study is to identify the relationship between socio-demographic characteristics, traffic rule violations, and traffic crashes among young drivers. Four main traffic rule violations are examined: red light violations, seat belt violations, speeding, and driving under the influence of alcohol, which are decisive in determining driving behavior and traffic crashes. The survey investigates the socio-demographic characteristics, traffic rule violation behavior and traffic crash histories of young adults. Four hypothetical scenarios were prepared for each traffic rule violation and data from the scenarios were modeled using the ordered probit model. Significant variables affecting each traffic rule violation are stated. Finally, significant variables that interact with crash involvements were investigated with binary logit models. According to the data analysis, 23.9% of drivers stated that they were involved in at least one traffic crash within the last three years. This crash rate increases to 38.3% for those who received at least one traffic citation/violation in last three years and peaks to 47.4% for those who were fined for seat belt violations in last three years.
Sosyo-ekonomik verilere dayanarak yapılan çalışmalara göre gençlerin trafik kural ihlallerine daha eğilimli olduğu ve tüm dünyada genç sürücülerin, özellikle heyecan arama ve tecrübesizlik nedeniyle, trafik kazalarında büyük rol oynadığı bilinmektedir, bu nedenle genç nüfusun yoğun olduğu ülkemizde genç sürücü davranışları incelenmelidir.
Bu çalışmanın ana hedefi; genç sürücülerin (18-29 yaş) trafik kurallarına ne kadar uyduklarını belirlemek ve genç sürücülerin sosyo-ekonomik yapıları, sürüş tecrübeleri gibi değişkenlerle trafik ihlalleri arasında bir ilişki olup olmadığını açıklamaya çalışmaktır.
Çalışmada sürücü eğilimlerinin saptanmasında ve trafik kazalarında belirleyici olan; kırmızı ışıkta geçme, emniyet kemeri takmama, hız sınırını aşma ve alkollü araç kullanma olmak üzere dört ana kural ihlali incelenmiştir. Genç sürücülerin trafik kural ihlalleri ile sürüş davranışları arasındaki ilişkileri detaylı incelemek için yapılan anket çalışması ile toplanan veriler bu çalışmada kullanılmıştır. Kişisel Bilgiler ve Kural İhlalleri grupları altında toplanan sorulardan oluşan anket çalışması Aydın ve Malatya İlleri Merkez İlçelerinde gerçekleştirilmiştir. sürücü ehliyetine sahip ve en az bir yıldır aktif olarak araç kullanan 18-29 yaş arası sürücüler hedeflenmiştir. Belirtilen özellikleri sağlayan, farklı eğitim ve gelir düzeylerine sahip, Aydın’da 417, Malatya’da ise toplam 400 genç sürücüye yüz yüze anket tekniği kullanılarak anket yapılmıştır.
Sürücülerin sosyo-ekonomik verileri ve sürüş davranışı verileri toplanmış ve bu değişkenler ile kural ihlali yapma eğilimi arasındaki ilişki ikili (binary) logit model kullanılarak incelenmiştir. Çalışma sonucunda genç sürücüler daha yakından tanınmış, gerçekleştirdikleri trafik kural ihlalleri, sürüş davranışları, sosyo-ekonomik ve demografik yapıları arasında ne gibi ilişkiler olduğu ortaya çıkarılmıştır.
Transportation-disadvantaged groups have been defined in previous studies as those who are low income earners, are family dependent, have limited access to private motor vehicles and public transport services, and are obliged to spend relatively more time and money on their trips. Additionally the disabled, young, and elderly are commonly considered to be among the transportation-disadvantaged. Although generally this definition seems correct, it is not specific enough to become a universal definition that could apply to all urban contexts. This paper investigates whether perceptions of travel difficulty vary as does the definition of transportation-disadvantaged in socioculturally different urban contexts. For this investigation, the writers undertake a series of statistical analyses in a case study of Yamaga, Japan, and compare the findings with a previous case study, in which the same methodology, hypothesis, and assumptions were applied to a culturally and demographically different settlement in Aydin, Turkey. After comparing the findings observed in Aydin with the statistical analysis results in Yamaga, this paper reveals that there can be no detailed, universal definition of the transportation-disadvantaged. The writers conclude that the characteristics of the transportation-disadvantaged are not globally identical, and policies and solutions that work in one locality may not have the same results in another sociocultural context.
This study investigates the effects of Transit Information Systems (TIS). TIS are wide range of systems that provide travelers information about travel options such as; travel times, delays and/or incidents. In this study, the important transit information types and their service levels are investigated in Izmir City, Turkey. The study focused on the transit users; considered information types for different transit mode segments were identified. In addition, accepted information types for non-transit users to consider transit as an alternative commute mode was investigated. For these purposes, a stated preference scenario was prepared which included the considered important information types of respondents and a function of their actual travel time. In this study, static pre-transit information systems were considered. Results indicated that considered TIS between transit and non-transit users are not much different from each other. However, considered TIS among different transit mode segments is significantly different.
Corrosion of Reinforcement (rebar) is nondestructively estimated by the half-cell potential measurement. As is the case with other nondestructive testings (NDT), understanding of the underlying principles should be clarified in order to obtain meaningful results. Therefore, the measurement of potentials in concrete is analytically investigated. The effect of internal defects on the potentials measured is clarified numerically by the boundary element method (BEM). Thus, a simplified inversion by BEM is applied to convert the potentials on concrete surface to those on rebars, taking into account the concrete resistivity. Because the potentials measured on concrete surface are so sensitive to moisture content, concrete resistivity and surface condition, an inverse procedure to convert the potentials on concrete surface into those on rebars is developed on the basis of BEM. It is found that ASTM criterion is practically applicable to estimate corrosion from the potential values converted. In experiments, an applicability of the procedure is examined by accelerated corrosion tests of reinforced concrete (RC) slabs. For practical use, the procedure is developed where results of IBEM are visualized by VRML (Virtual Reality modeling Language) in three-dimensional space.
In order to solve the traffic congestion problem, it is decided to convert some of the traffic from ordinary road to expressway with discounted toll. A route choice survey was conducted to freight and production companies to collect two different types of data; Revealed Preference (RP) and Stated Preference (SP). Estimation was done in four steps; segmentation model, a route choice model with RP data and a convert model with SP data. Finally, RP and SP data were combined in linear and non-linear models. It is identified that VOT follows a decreasing curve by increasing travel time.