Kent içi yollarda bisiklet-motorlu taşıt etkileşiminin yol güvenliği açısından incelenmesi
Analysis of bicycle-motor vehicle interaction on urban roads in terms of road safety
Yazar: EMRE SAK
Danışman: DOÇ. DR. HÜSEYİN ONUR TEZCAN
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Ulaştırma Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2024
Konu: Trafik = Traffic ; Ulaşım = Transportation

Özet:
Bisiklet, düşük çevresel etkileri ve insan sağlığı açısından sağladığı katkılar ile sürdürülebilir ulaşımın temel unsurlarından biridir. Bisiklet kullanımının yaygınlaştırılması, ulaşımın çevresel ve ekonomik etkilerini, kentlerdeki trafik tıkanıklığını, park talebini ve fosil yakıtlara bağımlılığı önemli ölçüde azaltmaya katkı sağlayabilir. Ancak, bisikletin faydalarına karşın, yol güvenliği ile ilgili endişelerin bisiklet kullanımının yaygınlaşmasında önünde önemli bir engel olduğu söylenebilir. 
Birçok kent içi yolda, bisiklet yolu/şeridi ve hız denetimli güvenli geçiş noktaları gibi temel altyapı eksikleri, bisiklet kullanıcılarının motorlu taşıtlar ile aynı yolu paylaşmasına neden olmaktadır. Özellikle böyle yollarda, bisiklet ile motorlu taşıtlar arasındaki etkileşim artmakta ve bu durum, bisikletlilerin güvenliğini olumsuz olarak etkilemektedir. Yol kullanıcıları arasında motorlu taşıtlara göre daha korunmasız ve hassas bir özellik gösteren bisikletliler, bu etkileşimlerde daha yüksek yaralanma veya ölüm riskiyle karşı karşıya kalabilmektedir. Bu yönüyle değerlendirildiğinde, bisiklet-motorlu taşıt etkileşimlerinin incelenmesi, bisiklet kullanıcılarının güvenliğini sağlamak açısından yaşamsal öneme sahiptir. Bu tez çalışmasında, bisiklet-motorlu taşıt etkileşimlerindeki motorlu taşıt, yol ve etkileşim özelliklerinin, bisiklet yol güvenliğine olan etkisini model geliştirilerek belirlenmesi amaçlanmıştır. 
Bu çalışmada, İstanbul'da, uzunluğu 2 km olan Üsküdar-Kuzguncuk sahil yolu kesiminde, bisiklet ile çeşitli gün ve saatlerde, toplam 2 saatlik saha gözlemi ile toplam 13 sürüş gerçekleştirilmiş ve sürüşler kamera ile kayıt altına alınmıştır. Gerçekleştirilen sürüşlerde, 437 motorlu taşıtın bisikletliyi sollama verisi analiz edilip, bisiklet sürücülerinin risk düzeyleri, motorlu taşıtın bisikletliye olan uzaklığına bağlı olarak düşük, orta ve yüksek olmak üzere 3 düzeyde belirlenmiştir. 
Saha gözlemi ile birlikte kamera görüntülerinden yararlanılarak 10 değişken için veri toplanmıştır. Bu değişkenler, motorlu taşıtın bisikletliye yatay uzaklığı başta olmak üzere; güvenlik uzaklığı, park eden taşıt olması, eğim özellikleri, sürekli ızgaranın varlığı, bisiklet ile etkileşime giren taşıt hızı, taşıtın türü, taşıtın korna çalması, taşıt sürücüsünün şerit ihlali yapması ve karşı yönden taşıt geçmesidir. Bisiklet risk düzeyinin bu değişkenler altındaki durumunu değerlendirmede kesikli seçim modellerinden biri olan çok terimli logit model (ÇTL) kullanılmıştır. 
Gözlemler sonucunda; 100 etkileşimin (%23) düşük, 208 etkileşimin (%47) orta ve 129 etkileşimin ise (%30) yüksek risk düzeyinde olduğu belirlenmiştir. Model katsayı kesitirim sonuçlarına göre ise; yolun çıkış veya iniş eğimli olmasının, etkileşim sırasında karşı şeritten taşıt geçmesinin ve sürekli ızgara bulunmasının bisiklet risk düzeyini arttırdığı görülürken, güvenlik uzaklığının artmasının, taşıt hızının yüksek olmasının ve taşıtın şerit ihlali yapmasının risk düzeyini azaltarak bisiklet yol güvenliğine olumlu etkisi olduğu görülmüştür. Sollama yapan taşıt türleri incelendiğinde, en riskli grubun otobüs ve minibüsler olduğu, en düşük riskli grubun ise otomobil olduğu belirlenmiştir.
Çalışma kapsamında oluşturulan model kestirim sonuçlarına ek olarak, elde edilen değişkenlerdeki gözlemlerin bazılarında değişiklik olduğu varsayılıp iki farklı senaryo uygulamasının bisiklet güvenliğine etkisi araştırılmıştır. Senaryo-1, model girdilerinden olan sürekli ızgaraların yol boyunca yerleştirilmesinin engellenmesi olarak belirlenmiştir. Senaryo-2'de ise, çalışma bölgesindeki çıkış eğimli yol kesimlerde güvenlik uzaklığının en az 0,90 m yapılması öngörülmüştür. Her iki senaryoda da yüksek risk düzeyinde kısmen azalma olurken, düşük risk düzeyinde bir miktar artış olmuştur. Bu senaryolar sonucunda, her iki senaryonun da risk düzeyini azaltmada olumlu etkisi olduğu görülürken, yol boyunca konumlanan sürekli ızgaraların aralıklı olması veya kaldırım tipi ızgara uygulaması ile yol kaplamasında sürüş sürekliliğini engelleyebilecek yapıların önüne geçilmesi ve çıkış eğimli yol kesimlerindeki güvenlik uzaklığının artırılmasının bisiklet güvenliğini arttırmada etkin bir çözüm olabileceği belirlenmiştir.

Abstract:
Cycling is one of the key elements of sustainable transport with its low environmental impacts and contributions to human health. Bicycle continues to be an important option, especially for urban trips, thanks to its flexibility and economy as well as being environmentally friendly. Many countries in the world are developing various policies to increase the share of cycling among all modes of transport. The widespread use of bicycles can contribute by helping to significantly reduce the environmental and economic impacts of transport, traffic congestion in cities, parking demand and dependence on fossil fuels. However, despite the benefits of cycling, road safety concerns create significant barriers to increase its share. High travelling speeds and heavy traffic can lead to various risks for cyclists.
On many urban roads, the lack of basic infrastructure, such as bike lanes and safe crossing points with speed controls, results in cyclists' sharing the same road with motorised vehicles. Especially on such roads, the interaction between bicycles and motor vehicles increases and this situation negatively affects the safety of cyclists. Cyclist are vulnerable users and they may face a higher risk of injury or death during these interactions. From this point of view, analysing bicycle-motor vehicle interactions is of critical importance to ensure the safety of bicycle users. In this thesis, it is aimed to determine the effect of vehichle, road and overtaking characteristics in bicycle-motor vehicle interactions on bicycle road safety by developing a model.
The study was conducted on the Üsküdar-Kuzguncuk coastal road section, which is 2 km long in Istanbul, with a total of 13 rides and 2 hours of field observations on various days and hours. A camera was placed on the back of the cyclist to obtain the data about road, vehicle and driver characteristics, especially the risk levels during the interaction. Throughout the rides, 437 motor vehicles overtaking cyclists were observed and the risk levels of cyclists were determined at 3 levels as low, medium and high by taking into account the distance to the cyclist of the motor vehicle at the moment of the overtaking. 
In determining the observation road, attention was paid to the fact that the selected section is a road used by bicycle users, there is one lane for each direction of traffic and the road is suitable for overtaking vehicles. In this way, it was aimed that motor vehicle-bicycle interaction would occur more frequently. At the same time, the fact that the road has different characteristics, the distance between the road edge line and the sidewalk varies continuously, there is a continuous grid at some parts of the road, parking spots are present and the slope of the road vary. All of these factors were effective in the route selection. 
Data collection was conducted by observations to identify road and environmental characteristics. In addition, the road edge line was followed primarily during the ride to provide that the motor vehicle interaction was independent of the position of the bicycle on the road. Furthermore, with the help of the on-road computer, the speed of the bicycle was kept at approximately 15 km/h, taking into account the average cyclist behaviour, except for small decelerations and accelerations on ramps and descents. By this way, it is aimed that the bicycle speed does not affect the overtaking process in motor vehicle-bicycle interactions. In additional, the beginning of the bicycle-motor vehicle interaction is determined as the situation when the vehicle following the cyclist approaches 15 metres to the bicycle.
Data were collected for 10 variables by utilising camera footages together with field observations. These variables are sidewalk safety distance, presence of parked vehicles, slope characteristics, presence of continuous grating, speed and proximity of the vehicle interacting with the bicycle, type of vehicle, honking by the vehicle, lane violation of the vehicle and vehicles passing from the opposite direction. 
In this study, the discrete choice model was used to evaluate the bicycle risk level in motor vehicle-bicycle interactions by utilizing selected variables. In this framework, model inputs were created according to vehicle types, road and interactions characteristics. Since the dependent variable consists of three options corresponding to different risk levels, the multinomial logit model (MNL), which is one of the discrete choice models that deals with the choice of a set of options based on random utility theory, was used. With the dummy variables, 11 variables were generated to provide input to the model. 
As a result of the observations, it was determined that 100 interactions (23%) were low risk, 208 interactions (47%) were medium risk and 129 interactions (30%) were high risk. According to the coefficient estimates, it was observed that the uphill and downhill slope of the road, passing vehicles from the opposite lane during the interaction and the presence of a continuous grating increased the bicycle risk level, while the lane violation of the motor vehicle, the increase in the sidewalk safety distance and vehicle speed had a positive effect on bicycle road safety by decreasing the risk level. Considering the overtaking vehicle types, it was found that the most risky group in terms of bicycle safety was buses and minibuses, while the lowest risk group was cars.
In addition to the model estimation results, the effect of two different scenarios on cycling safety was investigated by assuming that some of the variables were manipulated and modified. Scenarios were determined in such a manner that the changes considered are measures to reduce the level of cycling risk and have a practical aspect that can be applied in the real world. Accordingly, in scenario-1, it has been determined that some measures can be taken such as preventing the continuous gratings, which are one of the model inputs, from being positioned along the road. In Scenario-2, in order to provide a safe space between the bicycle and the sidewalk, it is considered that the safety distance between the road edge line and the sidewalk is at least 0.90 m on the uphill slope sections. Due to the fact that the 0.90 m safety distance may be difficult to be applied in the field along the entire road and this may also cause narrowing of the sidewalk width, it was considered that this application can only be applied on the uphill slope road sections. Thus, 2 different scenarios were determined as removing the continuous gratings in the safety distance and making the safety distance at least 0.90 m on the uphill slope sections on the study route.  
According to the estimation results, in two scenarios, there was a partial decrease in the high risk level and a slight increase in the low risk level. As a result of these scenarios, it is seen that both scenarios have a positive effect on reducing the risk level. In Scenario-1, it was concluded that bicycle safety can be increased by continuous gratings prevented from being located along the road with increasing spacing between the gratings or vertically set in the kerbs. In Scenario-2, due to the partial increase in the speed difference between bicycles and motor vehicles on uphill sloping road sections, motor vehicles tend to pass close to cyclists, negatively affecting bicycle safety, whereas providing a safe distance between the roadside line and the pavement increases bicycle safety by providing manoeuvring space for the cyclist during close interaction.  
In this thesis, the factors affecting road safety in bicycle-motor vehicle interactions were identified and scenarios for improvement applications were developed. In order to examine these factors, the video footages were analysed. The limitation of the study is these footages were analysed by a single user and the dependent variable used to determine the risk level was only the distance between the bicycle and the motor vehicle. In further studies, the more cyclist camera footages can be analysed from more cyclist to find an average risk perception level for each interaction by a group of cyclist. In addition, methods that can utilise more numerical data can be developed by reducing dummy variables during data collection.