Impact of pedestrian flows on traffic delays before roundabouts

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Impact of pedestrian flows on traffic delays before roundabouts

Romana Bura, Roman Rohalskyy, Lviv Polytechnic National University

Вплив пішохідних потоків на затримки транспорту перед саморегульованими перехрестями

У роботі розглянуто саморегульоване перехрестя, розташоване у житловому районі м. Львова. На локації розміщено багато точок притягання, тому інтенсивності транспортних та пішохідних потоків високі. На усіх підходах до перехрестя наявні нерегульовані пішохідні переходи, з яких на трьох відсутні острівці безпеки. Проведено натурні дослідження зі збиранням первинних показників транспортних та пішохідних потоків у пікові та міжпікові періоди. За допомогою програмного забезпечення PTV Vissim визначено затримки транспортних потоків на підходах до саморегульованого перехрестя за реальних умов руху. Запропоновано три варіанти влаштування пішохідних переходів на підходах до саморегульованих перехресть.

Перший варіант передбачав облаштування острівців безпеки на всіх пішохідних переходах. Другим варіантом було облаштування підземних пішохідних переходів. Третій варіант - впровадження адаптивного світлофорного регулювання з пристроєм виклику для пішоходів. Здійснено моделювання руху за усіх трьох запропонованих варіантів із визначенням затримки, яка припадає на один транспортний засіб, значень середньої та максимальної довжини черги транспортних засобів на підходах до саморегульованого перехрестя. Усі три варіанти показали кращі результати зменшення транспортної затримки, ніж за нинішніх умов руху. Проте спостерігалися затримки, спричинені самим транспортним потоком. Ці затримки визначено за результатами моделювання другого варіанта.

Ключові слова: транспортний потік; пішохідний потік; безпека руху; моделювання руху; нерегульований пішохідний перехід.

Introduction

Not enough attention is paid to road users who use alternative means of movement, namely walking, cycling, or electric scooters, to solve the problems caused by the increasing the number of cars in cities. Along with transport infrastructure, pedestrian and bicycle infrastructure in Ukraine is underdeveloped. Very often, there is an unsatisfactory condition of pedestrian paths, lack of bicycle paths, insufficient number of pedestrian crosswalks, or presence of underground or aboveground pedestrian crosswalks with missing ramps or elevators for people with reduced mobility.

At the same time, there is the issue of pedestrian accessibility to points of attraction, especially in residential areas. Cases are often observed when residential areas cross arterial streets of district or citywide significance. At the same time, schools, kindergartens, shopping centers, etc., are located on both sides of the street. At the same time, pedestrian crosswalks are either located in inappropriate places for pedestrians or are absent. Another problem is unsignalized pedestrian crosswalks on such streets. First, they create a danger to vehicles riding at higher speeds and having to slow down when pedestrians start to cross the roadway, and to pedestrians who may misjudge the intervals and start crossing the roadway when cars are close enough to create a dangerous situation. Pedestrians also tend to violate traffic rules, abusing their right of way when crossing unsignalized pedestrian crosswalks, not making sure the maneuver is safe, and suddenly entering the roadway. Secondly, high values of traffic and pedestrian volumes with uncontrolled crossing of the latter can cause significant delays for transport, especially during peak periods.

Roundabouts on arterial streets in residential areas require special attention. It is because at high values of traffic volumes and a significant share of left-turning flow the Sectoral Building Norms of Ukraine recommend designing large roundabouts (with a central island diameter of more than 60 m) [1]. Given the width of the roadway around this central island, the area of such intersections is very large and creates significant problems with pedestrian accessibility. Therefore, pedestrian crosswalks at such roundabouts are usually arranged as close as possible to the beginning of the circular flow to reduce the distances pedestrians should walk, that affects both traffic safety and traffic delays.

Research statement

Nowadays, in many large cities of Ukraine, including the city of Lviv, there are arterial streets in the residential areas with four or more lanes for traffic in one direction where significant volumes and speeds of traffic are presented. Residential areas mean unequivocally high volumes of pedestrian flows, especially during peak periods, when residents go to work, educational institutions, shopping centers, etc. Therefore, the problem of pedestrian accessibility in these areas should be solved first place. Namely, sufficient number of pedestrian crosswalks is needed while ensuring pedestrian safety and minimizing traffic delays. One more problem for pedestrians is the intersection of arterial streets, as their area is usually large, which creates additional inconvenience in getting to the destination. With lacking alternatives, pedestrians are forced to cross at such places. Given the high values of pedestrian volumes and frequent violations of traffic rules by pedestrians, it creates significant inconvenience for traffic flows approaching the intersections.

In the Frankivskyi district of Lviv city, there are three roundabouts with large areas, and many attraction points near them. In addition, they are located in a residential area. Pedestrian crosswalks are installed at the approaches to all these intersections. Some of them have safety islands, but all of them are unsignalized. During peak periods, there is an almost continuous flow of pedestrians trying to cross the roadway, so vehicles first must stop before the pedestrian crosswalks to let pedestrians through, then again before the circular flow to let through vehicles moving around the central island and finally when exiting the circular flow, to also allow pedestrian flows cross the roadway.

State construction norms of Ukraine [2] determine that on streets with two or more traffic lanes in one direction, it is necessary to arrange safety islands at unsignalized pedestrian crosswalks or to implement traffic light signaling. As for the construction of aboveground or underground pedestrian crosswalks, they can be arranged only on arterial streets with continuous traffic, in compliance with all requirements for people with reduced mobility.

Therefore, the aim of our study is to analyze the impact of pedestrian flows on the delays of traffic flows on the approaches to the roundabout. We considered four options: unsignalized pedestrian crosswalk without safety islands (existing traffic conditions), unsignalized pedestrian crosswalk with existing safety islands, signalized pedestrian crosswalk, and underground pedestrian crosswalk.

It is necessary to complete the following tasks to achieve the aim:

- carry out field studies at the roundabout in peak and off-peak periods to determine the primary indicators of traffic and pedestrian flows and existing traffic conditions at the intersection;

- carry out traffic simulation with the determination of the delay of vehicles on the approaches to the roundabout under existing traffic conditions;

- carry out traffic simulation for three options for arranging pedestrian crosswalks before roundabouts;

- provide recommendations on the expediency of using various options for arranging pedestrian crosswalks before roundabouts.

The analysis of the main literary sources

The interaction of traffic and pedestrian flows has been studied for a long time. The increasing number of cars causes delays for traffic and pedestrians who want to cross the roadway at unsignalized pedestrian crosswalks. Conversely, the significant pedestrian volumes in places of concentration of attraction points can have a negative impact on traffic delays.

The authors [3] draw attention to the impact of pedestrians crossing the roadway in unauthorized places on traffic flow delays. It was found that smaller vehicles, due to their larger maneuverability, had slightly lower delay values than trucks. In general, the violation of traffic rules by pedestrians led to forming the conditions corresponding to the level of service E, which is close to traffic jam conditions. Therefore, the authors concluded that it is necessary to improve the pedestrian infrastructure and increase the number of pedestrian crosswalks in locations with high pedestrian volumes to prevent the formation of such situations.

The authors [4] studied traffic delays before unsignalized pedestrian crosswalks on different types of sections: in the area of the intersection and outside it. It was determined that the highest delays were observed at intersection in secondary directions. It is because here, the vehicles were affected not only by pedestrians crossing the roadway, but also by vehicles moving along the main road.

The authors [5] point out that at unsignalized pedestrian crosswalks, significant traffic delays are created by pedestrians waiting to cross directly on the roadway, forcing drivers to brake urgently. Therefore, the authors recommend strictly regulating the places allowed for pedestrians to wait on the roadway.

Analysis of pedestrian behavior is one of the most difficult issues in studying the interaction of traffic and pedestrian flows. In a study [6], the behavior of pedestrians when crossing unsignalized pedestrian crosswalks was studied. Roundabouts were investigated here. It was determined that pedestrians who crossed the roadway on the main street, where higher traffic volumes were observed, violated traffic rules less. In addition, the authors include older people and those who crossed a wider roadway into this category. As for violations of traffic rules on secondary roads, they mainly occurred because people had a long way to go to the pedestrian crosswalk.

The authors [7] investigated the effectiveness of relocating pedestrian crosswalks from the intersection zone to the street section between two intersections. From the view of transport, this scenario is efficient, but the authors agree that the absence of pedestrian crosswalks at the intersection will encourage pedestrians to cross the roadway in unauthorized places with violation of traffic rules.

In general, the issue of pedestrian accessibility is quite relevant, especially in the case of roundabouts, since they occupy large areas of the road network. In addition, pedestrians create obstacles in the movement of traffic since the latter must stop before the pedestrian crosswalks for priority passage of pedestrians through the roadway. Such situations create delays in the movement of cars and reduce the capacity of the roundabout. Thus, the authors [8, 9] indicate that the presence of unsignalized pedestrian crosswalks immediately before the roundabout, especially when there is only one traffic lane, significantly reduces the capacity of these lanes when exiting the intersection. In addition, vehicles that exit the intersection and are forced to stop before the pedestrian crosswalk block traffic on nearby approaches to the intersection. The solution is to move the pedestrian crosswalks outside the roundabout, which, according to the authors, increases the capacity of the traffic lane when exiting the roundabout by 10 % [8].

The authors [10-12] also studied the capacity, but on the approach to roundabouts, taking into account the movement of pedestrians at unsignalized pedestrian crosswalks. The authors [10] studied the conditions under which pedestrians are allowed to move through the territory of a roundabout. The results showed a negative impact of increasing the pedestrian volume on the capacity of approaches to a roundabout. For example, data are provided that with the same traffic volume of 500 p.c.u./h, the capacity in the absence of pedestrians and with their volume of 350 ped./h is reduced by more than half.

The authors [13-15] concluded that safety islands at unsignalized pedestrian crosswalks before roundabouts makes the crosswalk safer and more predictable for pedestrians. In addition, the authors [13] point out that with a dividing line, pedestrians can cross the roadway outside the pedestrian crosswalk. If there is no safety island, pedestrians cross the roadway more carefully and in compliance with traffic rules. Therefore, the authors advise, along with the installation of safety islands, the installation of pedestrian fences to limit the access of pedestrians to the roadway outside the designated space. The authors of [16] generally point to the positive effect of applying various solutions, such as a flashing yellow signal, safety islands, and the introduction of traffic light signaling, on increasing pedestrian safety at roundabouts.

As for the implementation of traffic light control at roundabouts, the results of studies of the effectiveness of installing traffic lights at pedestrian crosswalks before roundabouts using a cellular automaton model are given in [17]. Two options were considered: a traffic light with a call button for pedestrians and a conventional traffic light with fixed-time control. It has been determined that with high volumes of traffic and pedestrians, it is more appropriate to install a traffic light with a call button since, in such a case, lower values of delays for transport are observed. Implementing traffic signals is generally ineffective solution at low traffic and pedestrian volumes. The authors also point out that pedestrians create obstacles for cars when exiting a roundabout, even at low pedestrian volumes. The authors [18] propose the arrangement of an adjustable stepped pedestrian crosswalk to reduce traffic delays at roundabouts. Its essence is that at the entrance to the intersection, the pedestrian crossing is located closer to the central island than at the exit from the roundabout. The authors also suggest implementing traffic light control with priority given to pedestrians if their volume is low and to vehicles if pedestrian volume increases.

Research results

The intersection of Kulparkivska - Vyhovskoho - Volodymyra Velykoho Str. was chosen to study the influence of pedestrian flows on vehicle delays before roundabouts. PTV VISSIM software was used to simulate traffic and pedestrian flows. All the streets on the approaches to the intersection are arterial streets with two lanes in each direction.

There are several points of attraction nearby - office premises and a shopping center. Therefore, high values of traffic and pedestrian volumes are observed. There is an unsignalized pedestrian crosswalk without safety islands at each approach to the intersection. The only existing safety island is present at the approach to the roundabout from the side of Kulparkivska Street in the direction of the city center. The intersection is large in area - the radius of the central island is 34.1 m, which makes it possible to classify the roundabout as large, according to the classification of roundabouts [1]. The scheme of the roundabout, drawn in the PTV VISSIM software, with located road signs, is shown in Fig. 1.

Fig. 1. Scheme of researched roundabout

At the intersection, field studies of traffic and pedestrian volumes during the peak (morning peak period - from 9:00 to 10:00, lunch peak period - from 13:00 to 14:00 and evening peak period - from 18:00 to 19:00) and off-peak (from 11:00 to 12:00) periods were carried out. Summary values of traffic volumes for each peak and off-peak period are given in Table 1, the pedestrian volumes - in Table 2.

Table 1. Results of the study of traffic volumes at researched roundabout