Investigating Parameter Interactions with the Factorial Design Method: Webster’s Optimal Cycle Length Model

Accurate estimation of cycle length is an important factor in the performance of a signalized intersection. Cycle length is determined by employing some parameters such as arrival flow, number of phase, lost time etc., but each parameter has different effects on a cycle length model. If the effects of parameters and their interactions in the cycle length model are known, the performance of the model can be effectively increased. In this study, the sensitivity of optimal cycle length model proposed by Webster and its parameters were analysed with the factorial design method. The reason for selecting this model is that the model has still been used in signal timing practice and has lead many studies of researchers over 50 years. The evaluation of sensitivity analysis shows that while arrival flow as single parameter has a major effect on the optimal cycle length model, the remaining single parameters of the model (i.e., the number of phase in a cycle length, saturation flow and lost time) have secondary importance. Additionally, two parameter interactions of arrival flow-saturation flow have major effect on the model results. For three parameter interactions, the number of phase-arrival flow-saturation flow interaction has a slightly larger effect than the other three-parameter interactions. As a result, the factorial design method is an effective tool to determine the importance of the model parameters for researchers, and it can be employed to other traffic engineering applications

An artificial intelligent approach to traffic accident estimation: Model development and application

This study proposes an Artificial Neural Network (ANN) model and a Genetic Algorithm (GA) model to estimate the number of accidents (A), fatalities (F) and injuries (I) in Ankara, Turkey, utilizing the data obtained between 1986 and 2005. For model development, the number of vehicles (N), fatalities, injuries, accidents and population (P) were selected as model parameters. In the ANN model, the sigmoid and linear functions were used as activation functions with the feed forward‐back propagation algorithm. In the GA approach, two forms of genetic algorithm models including a linear and an exponential form of mathematical expressions were developed. The results of the GA model showed that the exponential model form was suitable to estimate the number of accidents and fatalities while the linear form was the most appropriate for predicting the number of injuries. The best fit model with the lowest mean absolute errors (MAE) between the observed and estimated values is selected for future estimations. The comparison of the model results indicated that the performance of the ANN model was better than that of the GA model. To investigate the performance of the ANN model for future estimations, a fifteen year period from 2006 to 2020 with two possible scenarios was employed. In the first scenario, the annual average growth rates of population and the number of vehicles are assumed to be 2.0 % and 7.5%, respectively. In the second scenario, the average number of vehicles per capita is assumed to reach 0.60, which represents approximately two and a half‐fold increase in fifteen years. The results obtained from both scenarios reveal the suitability of the current methods for road safety applications. First published online: 27 Oct 201

Development of Cycle Length Models using Flower Pollination Algorithm for Isolated Signalized Intersections

Son zamanlarda nüfus ve ekonomideki büyüme karayollarında araç kullanımını arttırmakta, buna bağlı olarak da kavşakların kapasitesi yetersiz kalmaktadır. Kavşakların verimsiz çalışmasından dolayı gecikme, yakıt tüketimi, emisyon salınımı artarken sürücü davranışları da olumsuz etkilenmektedir. Kavşak geometrilerinin iyileştirilmesinin yanı sıra, optimum devre süresinin doğru tespiti ve sinyal sürelerinin düzenlenmesi ile de bu sorunların minimuma indirilebilmesi mümkün olmaktadır. Bu çalışmada Çiçek Tozlaşma Algoritması (ÇTA) kullanılarak optimum devre süresi modelleri geliştirilmiştir. Ayrıca en düşük gecikmeye sahip olan devre sürelerinin belirlenmesinde Diferansiyel Gelişim Algoritmasından (DGA) yararlanılmıştır. Kalibre edilen Webster modeline ilave olarak sabit eklenmiş Webster model formu ve üstel formda devre süresi modelleri geliştirilmiştir. VISSIM simülasyon programı ile elde edilen gecikme değerlerine göre geliştirilen bütün modeller Webster modeli ve VISTRO optimizasyon programı ile karşılaştırılmış ve önerilen modellerin istatistiksel olarak daha iyi performansa sahip olduğu görülmüştür. Bu modellerin özellikle yüksek trafik hacmine sahip trafik durumlarında yetersiz kalan Webster modelindeki eksiklikleri kapatarak alternatif bir devre süresi tahmin modeli olarak kullanılabileceği ön görülmektedir.Recently, the growth in population and economy has increased the use of vehicles on highways and accordingly the capacity of the intersections is insufficient. Delay, fuel consumption and emissions are increased due to the inefficient operation of intersections, and driver behavior is adversely affected. In addition to improving intersection geometry, by correct determination of optimum cycle length and arrangement of signal times, it is possible to minimize these problems. In this study, optimum cycle length models have been developed by using Flower Pollination Algorithm (FPA). Additionally, Differential Evolution Algorithm has been used to determine the cycle length which has the minimum delay value for each traffic situation. In addition to the calibrated Webster model, Webster model with constant form and exponential form have been developed as cycle length models. All models developed according to the delay values obtained with the VISSIM simulation program were compared with the Webster model and the VISTRO optimization program and the proposed models were found to have statistically better performance. It has been seen that these models can be used as an alternative cycle length estimation model by defeating the deficiencies in Webster model which is insufficient especially in traffic situations with high traffic volume

Mathematical modeling of delay estimation at signalized intersections I: A new time-dependent delay model for various analysis time periods

Gecikme, trafik sinyal zamanlarının optimizasyonunda ve bir sinyalize kavşağın hizmet seviyesinin belirlenmesinde kullanılan önemli bir faktördür. Bu makalede, sinyalize kavşaklarda gecikmeyi tahmin etmek için farklı bir yöntem kullanılarak zamana bağlı bir gecikme modeli geliştirilmiştir. Bu modelin en önemli özelliği gecikme değişkeni k'nm literatürde yaygın olarak bilinen diğer modellerde olduğu gibi sabit bir sayı olmayıp, çözümleme süresinin bir fonksiyonu olarak ifade edilmesidir. Böylece sinyalize kavşaklarda gecikmenin değişen çözümleme süreleri için daha doğru tahmin edilmesi mümkün olacaktır. Geliştirilen model ile mevcut olan modellerin gecikme tahminleri karşılaştırıldığında, geliştirilen modelin değişen zaman koşullarını da göz önüne aldığından mevcut gecikme modellerine göre daha güvenilir olduğu görülmektedir.Delay is an important factor in the optimization of traffic signals and the determination of the level of service of a signalized intersection. In this paper, using a different methodology a new time-dependent delay model was developed to estimate delay at signalized intersections. The most important feature of the proposed model is that it utilizes the delay parameter k as a function of analysis period instead of a fixed value used by the existing delay models. Therefore, the new model can produce more reasonable delay estimations at signalized intersections for variable time periods. A comparison of the delay estimations by the new model and the existing four different models indicated the delay estimations by the new model appear to be generally better than those by the other models

Mathematical modeling of delay estimation at signalized intersections II: The analysis of proposed delay model dependent on variable demand and time conditions

Bu makalenin amacı, bir önceki makalede geliştirilen gecikme modelinin TRAF-NETSIM benzetim programı yardımı ile değişen, akım ve zaman koşullarına bağlı olarak ve özellikle de aşırı doygun trafik akımlarını da göz önüne alarak güvenirliliğini araştırmak ve modeli geçerli kılmaktır. Bu amacı başarmak ve gecikme modelini test edebilmek için benzetim tekniğine dayanan bir çalışma yapılmış ve değişik trafik ve zaman koşullarını yansıtması için 48 adet farklı senaryo tasarlanmıştır. Benzetim modelinden elde edilen gecikme tahminleri ile geliştirilen modelden elde edilen gecikme tahminleri doğrusal regresyon çözümlemesi kullanılarak istatistiksel olarak karşılaştırılmıştır. Çözümleme sonuçları modelden ve simülasyondan elde edilen gecikme tahminlerinin birbirine yakın olduğunu göstermiştir.The objective of this study is to calibrate and verify the delay model developed in the accompanying paper using TRAF-NETSIM simulation program. The model is time-dependent for signalized intersections suitable for variable demand and time conditions including oversaturated conditions. In the calibration and verification of the model, a simulation study was performed to produce the various traffic and time conditions using 48 different scenarios. The delays obtained from the simulations and the proposed model were statistically compared using linear regression analysis. The results indicated a good agreement between delays generated by the simulations and delays estimated by the proposed model

Estimating Traffic Accidents in Turkey Using Differential Evolution Algorithm

Estimating traffic accidents play a vital role to apply road safety procedures. This study proposes Differential Evolution Algorithm (DEA) models to estimate the number of accidents in Turkey. In the model development, population (P) and the number of vehicles (N) are selected as model parameters. Three model forms, linear, exponential and semi-quadratic models, are developed using DEA with the data covering from 2000 to 2014. Developed models are statistically compared to select the best fit model. The results of the DE models show that the linear model form is suitable to estimate the number of accidents. The statistics of this form is better than other forms in terms of performance criteria which are the Mean Absolute Percentage Errors (MAPE) and the Root Mean Square Errors (RMSE). To investigate the performance of linear DE model for future estimations, a ten-year period from 2015 to 2024 is considered. The results obtained from future estimations reveal the suitability of DE method for road safety applications

Analyisis of transportation systems and transportation policies in Turkey

Sosyo-ekonomik ve sosyo-kültürel yapılaşmanın doğal bir sonucu olarak ortaya çıkan ulaştırma talebi değerlendirilirken, ulaştırma sistemlerinin bir bütün olarak ele alınarak incelenmesi gereklidir. Gerek yolcu, gerekse yük taşımacılığı için seçilecek olan ulaştırma sisteminin hızlı, ekonomik, güvenli, çevreye az zarar veren ve ülke koşullarına uygun bir ulaştırma sisteminin olması arzu edilir. Ancak bir sistemin, sıralanan bu hususların hepsini birden bünyesinde toplaması oldukça zordur. Her sistemin birbirlerine göre üstünlükleri ve sakıncaları vardır. Bu nedenledir ki, büyük yatırımlar ülke genelinde tesis edilirken ileriye yönelik çok kapsamlı planlamalar yapılmalıdır. Ayrıca ülke kaynaklarının ulaştırma sistemleri arasında akılcı bir şekilde nasıl dağıtılması gerektiği araştırılmalı ve ulaştırma sistemleri arasında koordineli çalışmayı sağlayacak bir ulaşım planı hazırlanmalıdır. Bu planın başarısı ise hiç kuşkusuz sistemlerden birine ağırlık vermek yerine kombine taşımacılık ile mümkün olacaktır. Ülkemizin üç yanı denizlerle çevrili iken deniz yolu ile yapılan taşımacılığın % l seviyesinin çok altında olması ve karayolu ile yapılan yük ve yolcu taşımacılığının ise % 95 seviyelerine çıkması Türkiye'deki ulaştırma politikalarının sorgulanması gerektiğini ortaya çıkarmaktadır. Bu bildiride Türkiye'deki ulaştırma sistemlerinin ve ulaşım politikalarının tarihsel süreç içerisinde genel bir değerlendirmesi yapılarak sorunlar ortaya konulmakta ve çözüm önerilen sunulmaktadır.Transportation systems have to be considered and analysed as a whole while transportation demand, becoming as a natural outcome of socioeconomic and socio-cultural structure, is being evaluated. It is desired that transportation system, which will be selected for both passenger and freight transport, should be rapid, economic, safe, causing least harm to environment and appropriate for the conditions of a country. However, it is difficult for a transportation system to have all these properties. Every transportation system has advantages and disadvantages over each other. Therefore, comprehensive plans for future periods have to be prepared and how the sources of the country should be reasonably distributed among transportation systems must be investigated. Also, transportation plans have to be prepared to get coordinated operations among transportation systems while great investments are instituted in the entire country. There is no doubt that it is possible with combined transportation instead of concentration on one transportation system. Transportation policies in Turkey should be questioned since the level of highway transportation usage reaches to 95 % and level of sea transportation usage drops to less than 1 % in spite of being surrounded with sea in three sides of our land. In this paper, transportation systems and transportation policies in Turkey are evaluated in general and problems are analysed. Proposals are presented for the solutions of these problems

An analysis of type I dilemma zone at signalised intersections

Intersections, for vehicles coming from different directions, are conflict points in road networks. When a driver approaching a signalised intersection encounters the yellow light, he/she is in a dilemma either to safely stop or to pass through the intersection during clearance time. The decision to stop or to pass may change depending on some factors such as duration of yellow light, deceleration and acceleration rate, width of intersection, speed and length of vehicle, etc. This study aims to put forth the effects of some related factors affecting the length of the Type I dilemma zone. To perform this study, five factors including vehicle speed, maximum deceleration rate, perception-reaction time, clearance time, the total intersection width-vehicle length were considered and a total of 648 different traffic cases were investigated. The study results showed that the Type I dilemma zone length increased with the increase of speed, total intersection width-vehicle length and perception-reaction time, but decreased with the increase of clearance time and deceleration rate

Modeling of traffic signals syncronisation effect for vehicle emission reduction

Bu makalede Kırıkkale İli Millet bulvarında yer alan 4 sinyalize kavşak ve 5 cadde dilimi üzerinde; kesikli ve yeşil dalga senaryolarına göre taşıt emisyonlarının değişimi modellenmiştir. Bu amaçla, cadde üzerindeki dilimlerde taşıt sayımları yoluyla trafik hacmi ve seyir hızları bulunmuş, kavşaklarda bekleme süreleri tespit edilmiş ve mevcut kesikli duruma göre taşıt kaynaklı emisyonlar bulunmuştur. Daha sonra yeşil dalga etkisini görmek için 50 km/h sabit hızla seyir halinde ve ışıklı kavşakların birinde bekleme yoluyla emisyonların azalması modellenmiştir. Sonuçta yeşil dalga senaryosunun taşıt emisyonlarını genelde % 77,3 oranında azalttığı görülmüştür. Yeşil dalga senaryosunun; cadde emisyonlarını % 3,0 arttırmasına rağmen, kavşaklardaki; beklemelerde % 80,7 ve kalkışlarda % 77,4 azalma sağlandığı görülmüştür. Yeşil dalga senaryosunun en büyük avantajı, kirleticiler içinde en büyük payı oluşturan CO kirleticisinin % 76,7 oranında düşmesidir.In this study, the change of vehicle emissions in four signalized intersections and along the five streets in Millet Boulevard of Kırıkkale are modeled according to scenarios of interrupted flow and green (flow) wave. For this purpose, volumes and traveling speeds along the streets and waiting times (delay) in intersections are obtained by vehicle counting methods in these locations. Vehicle based emissions for present interrupted conditions are determined. Afterwards, to examine the effect of green wave, reductions in vehicle emissions are modeled for 50 km/h constant speed and stopping in only one signalized intersection case. It was observed that green wave scenario reduced the vehicle emissions by 74.0 % in general. It was also observed that by green wave scenario, emissions in streets were increased by 3.8 % while emissions during stopping and starting in intersections were decreased by 18.2 % and 22.6 %, respectively. The most important advantage of green wave scenario is that CO pollutant, the biggest share among pollutants, were decreased by 76.8 %