1. Introduction
Statistical data indicate a continuous increase in the migration of people from rural areas to cities. In 1950, only 30% of the population was urban dwellers, by 2018 this figure was 55%. According to estimates, by 2050 from 66% to 80% of the population will live in cities [
1]. Now we have the opportunity to observe the next phase of urbanization, which is suburbanization. It is a phenomenon of urbanization in the suburban area. The increase in the level of urbanization and suburbanization indicate great development potential of urban and suburban areas. However, as the number of city dwellers increases, it is becoming increasingly difficult to meet their public service needs and maintain a high level of comfort.
With the increase in the level of urbanization, an increase in the volume of global goods exchange has been observed for decades, which directly translates into an increase in the role of freight terminals and distribution facilities. Supply chains are critical now and their number and complexity continue to increase. Internet access contributed to this, and caused radical changes in the structure of the supply chain [
2]. Additionally, the human factor seems to be more important in the functioning of supply chains. Currently, supply chain stakeholders focus on meeting customer requirements, timely deliveries, and making sustainable decisions in order to survive in a competitive environment. In order to meet consumer expectations, companies have started to invest in projects aimed at sustainable development [
3,
4]. Stakeholder coordination and collaboration becomes essential to increase the efficiency of supply chains [
5]. Cities are important in this as the place where the actors in the supply chain are functioning, and they are often the end point of delivery transport, becoming a place of last mile deliveries. Research in this area shows that the last miles contribute from 13% to 75% of all transport costs. Last mile logistics is often described as the wasteful, most expensive, and polluting air and environmental part of the supply chain [
6]. Increasing the intensity of freight flow is exacerbating the problems of transport congestion, air and noise pollution, Greenhouse Gas (GHG) emissions, and the destruction of transport infrastructure and road accidents [
7].
The high rate of urbanization and the development of its subsequent phases contribute to a continuous increase in demand on the real estate market, which determines the demand for construction services, both in city centers and suburban areas [
8,
9]. The market situation applies to all types of works: Construction of buildings (residential and non-residential), specialized construction works, and construction of civil engineering facilities.
Construction is becoming a key element in urban development. The economic situation in the industry determines the increase in the number of enterprises offering construction services and projects implemented by them [
10]. This fact contributes to the increase in the number of freight transport for procurement purposes and causes an increase in conflicts between road users [
11]. In the conditions of competition, enterprises strive to best meet the needs of customers in response to the growing requirements in terms of timeliness, quality, and individualization of implemented construction projects. All key actors in construction supply chains are increasingly using the concept of “just-in-time” for this purpose [
12]. However, the faster development of the industry and the construction technologies used does not solve the problems associated with the negative impact of the implementation of construction projects on the functioning of cities. The negative effects accompanying the supply processes necessary for the implementation of construction projects are air pollution, exceeding the permissible noise emission standards, the occurrence of transport congestion and the impact on the level of road safety.
The aim of the study is to analyze and answer the question of whether there is a connection between the implementation of construction supplies and the occurrence of road traffic hazards in cities on the example of Szczecin. Due to the specificity of various types of construction works, only construction projects aimed at constructing buildings were qualified for the purposes of the article.
5. The Impact of Construction Supplies on Road Safety
5.1. Research Methodology
In pursuit of the research goal, the data triangulation method was used, which allowed the authors to take a broader look at the subject of the study, both in time and spatial perspective. The choice of the research method was determined by the possibility of collecting complete data for analysis while eliminating subjectivity. By combining different methods, authors in one study avoid the lack of accuracy resulting from the use of one method.
Desk research and statistical data analysis were carried out. In addition, structured observation and structured interview with contractors was used to select study objects. The research covered construction projects implemented since 2016. The selection of the examined objects was based on the following criteria: Location, occurrence of “bottlenecks”, size of the building, number of subcontractors, type of construction, duration of the project.
The analysis of road accidents in the area of selected construction projects in the city of Szczecin is possible only in terms of the characteristics of their occurrence. A limitation of the study is that participants can become perpetrators of road accidents. The data on road accidents collected in Poland has numerous limitations and shortcomings. One of them are road incidents that have not been notified to the relevant services. Referring to the good practices of other countries, attention should be paid to the detail of road accidents depending on the injuries sustained by the injured, providing information about the vehicle involved in the accident and many other factors [
61].
The article is organized as follows. In addition to the introduction, Chapter 2 is divided into three parts and covers road safety in cities. Chapter 3 is divided into two parts, and discusses construction procurement in terms of its impact on urban traffic. Chapter 4 presents an analysis of road accidents based on the example of the examined city. Chapter 5 presents the study of the impact of construction supplies on road safety. Finally, Chapter 6 presents the conclusion.
5.2. Characteristics of the Research Sample
The research was conducted in the city of Szczecin, which is a city with powiat rights, the capital of the West Pomerania, and the largest city in the region [
62]. Szczecin is a rapidly growing metropolis characterized by economic development, which contributes to the increase in the number of construction projects implemented. Recent years have also been characterized by a growing number of construction companies carrying out all types of construction works in the city. At the end of 2015, their number was 7764. At 1 of September 2019, this number was already 8453 [
10], which means an increase of about 8.9%.
The article takes into account the location of the construction projects carried out in the area of the city center of Szczecin, in the area covering a large part of enterprises, shopping centers, administrative buildings, schools, universities, and other key units. The difficulty in designating the city center in Szczecin resulted from its polycentric structure [
63]. In Szczecin, there are no general restrictions on the possibility and hours of truck entry into the city. These restrictions only apply to certain streets. For research purposes, the qualified construction projects did not have such restrictions.
To standardize the research sample, only construction works related to the erection of buildings and specialized construction works (Polish Classification of Activities (PKD) F41 and F43) were considered in the article. An additional criterion for choosing construction projects was their type. Only residential and non-residential buildings were considered (
Section 1 of the Polish classification of buildings). For research purposes, all facilities were also divided by size (small to 999 m
2, medium from 1000 to 9999 m
2, large from 10,000 m
2). Medium and large construction projects were qualified for the study due to the amount and kind of supplies needed for the supply. Standardization of the research sample also made it possible to determine the type of deliveries carried out during construction. Masonry and plastering, concrete, painting, roofing, welding, and other works were performed on all facilities. Supply for the purposes of their implementation was realized both directly from material producers and construction wholesalers. Depending on the size, deliveries were made both by transport up to 3.5 tons and by high-tonnage transport. Due to the uniformity of the sample, the types of building materials supplied were not included in the study.
Construction projects were also analyzed in terms of the number of subcontractors. Construction carried out by 0–9 subcontractors was considered to be carried out with a small number of subcontractors, from 10 to 19 as implemented by the average number of subcontractors, 20 and more as carried out by a large number of subcontractors. The number of subcontractors may affect the number of deliveries carried out. For qualified construction projects, areas adjacent to the construction site have been determined, which may be affected by the implementation of transport for supply purposes. Adjacent streets and intersections were taken as such areas.
5.3. Results of Study on the Impact of Construction Supply on Road Safety
The construction projects selected for the study are presented in
Figure 1. According to the adopted criterion, they are located in the city center, close to the so-called bottlenecks. All objects met the assumed research criteria.
Table 5 presents the detailed characteristics of selected construction investments.
Particularly noteworthy is the fact that the implementation of the Hanza Tower began in 2011, but it was only in 2012 that the first works began. In Spring 2013, at the preparatory stage, construction was suspended. It was not until 2017 that the work was resumed [
64].
To determine the changes in the level of safety in areas adjacent to construction sites, the number of accidents in the year preceding the year of construction beginning was examined, as well as the average number of accidents per year during the construction investment. For research purposes, in the case of Hanza Tower, 2016 was adopted as the year preceding the start of construction (the year before work resumed).
Table 6 shows the number of road accidents before construction projects are started and the average number of road accidents during construction and their characteristics.
In the case of Hanza Tower and Black Pearl, the average number of accidents during construction was higher than in the year preceding the start of the project. Research results regarding Nautica III indicate that the number of accidents was similar. During the implementation of Nautica IV, the number of accidents has significantly decreased. The number of road accidents in areas adjacent to the reconstruction square of the Hurt market was 0, and one road incident was noted in the year preceding the reconstruction. These results may be related to the location characteristics of the implemented construction project. The close occurrence of only a roundabout and a two-lane two-way road without the possibility of turning may reflect the above result. The most common road accidents were side/rear/frontal collisions. Equally frequent were car-to-pedestrian accidents.
6. Conclusions
The implementation of construction projects in cities is a serious challenge for contractors both due to the specificity of the works and organizational difficulties, especially in the field of construction supply. An additional problem is safety, which must be ensured not only on the construction site, but also in the adjacent areas. Due to the frequent need for changes related to temporary and permanent land use, all road users may be additionally exposed to road hazards. For this reason, the aim of the article was to analyze and answer the question whether there is a connection between the implementation of construction supplies and the occurrence of road traffic hazards in cities on the example of Szczecin. In addition, the article aims to find solutions to reduce the number of road accidents and increase road safety. The conducted research also revealed the weak points of the system of collecting and analyzing data on road accidents. The research covered selected areas in the center of Szczecin, where construction projects have been implemented since 2016 and road accidents occurred. The reference year is the year preceding the start of construction.
Five selected construction projects were qualified for the study, meeting specific criteria, which included: Location, type of building, size, type of performed works, number of subcontractors. Depending on the size, deliveries were made both by transport up to 3.5 tons and by high-tonnage transport. The study on five selected construction projects meeting the criteria has shown that their implementation may have an impact on the level of safety in the areas adjacent to the construction site. The most common road accidents were side/rear/frontal collisions. Equally frequent were car-to-pedestrian accidents. However, the unequivocal statement of relationship between implementation of construction projects and level of safety must be supported by extended research, covering a greater number of projects, additional consideration of the number of deliveries for supply purposes and the characteristics of vehicles involved in road incidents, as well as their detailed description. An important aspect in the analysis of the relationship between the implementation of construction projects in cities and the accident rate is the length of construction investments and stages of construction.
In order to increase road safety in the context of ongoing delivery transport for construction supply purposes, it seems reasonable to expand the infrastructure surrounding the construction site with particular emphasis on unloading places, optimize the supply system, and implement solutions in the field of transport telematics, both in infrastructure elements and means of transport. In addition, the results of the Australian study on implementing high productivity freight vehicles in urban areas [
65] show the need for consolidation of supplies to reduce the number of accidents.
As part of the research, it turned out that there is a serious problem related to the process of collecting and analyzing data related to the level of road safety. The available data is scattered, incomplete and, above all, does not take into account vehicle classification. It seems justified to extend the scope of collecting various data by competent authorities. It is helpful to locate road accidents on the map with the description of the accident occurrence characteristics, date, and time. However, it seems reasonable to extend them with information about the perpetrator of the accident, such as gender and age, as well as describing road conditions and visibility [
60,
61]. It seems reasonable to follow the experience of collecting data in other cities, e.g., in Abu Dhabi where descriptive statistics of data collected by the police contains a breakdown of road accidents according to the variable such as: Gender, age category, seat belts, seat damage, road classification, speed limit, lanes, and type of accidents [
66].
The practice of other countries shows that the larger data sets we have, the more efficiently and effectively we can select and implement various types of solutions. The implementation of activities aimed at sustainable development, such as reducing noise and greenhouse gas emissions, requires access to up-to-date data. They can significantly support local authorities in taking action in the context of urban logistics. The more that the subject of data collection and processing is common, and setting goals to reduce the negative effects of the urban transport system has become a priority for city, state, and EU managers.
The research carried out for the purpose of this article indicated the need to continue and deepen the research on the impact of the implementation of construction supplies on the level of road safety in order to unequivocally establish the dependencies. In addition, the need to transfer the detected defects in the collection and analysis of accident data to appropriate authorities for the purpose of improvement and improvement was indicated.