Forecasting the future levels of air pollution provides valuable information that holds importance for the general public, vulnerable populations, and policymakers. High-quality data are essential for precise and reliable forecasts and investigations of air pollution. Missing observations arise when the sensors utilized for assessing air quality parameters experience malfunctions, which result in erroneous measurements or gaps in the dataset and hinder the data quality. This research paper presents a novel approach for imputing missing values in air quality data in a univariate approach. The algorithm employs the random forest (RF) algorithm to impute missing observations in a bi-directional (forward and reverse in time) manner for air quality (particulate matter less than 2.5 μm (PM_2.5)) data from the Republic of Serbia. The algorithm was evaluated against simple methods, such as the mean and median imputation methods, for missing observations over durations of 24, 48, and 72 h. The results indicate that our algorithm yielded comparable error rates to the median imputation method for all periods when imputing the PM_2.5 data. Ultimately, the algorithm’s higher computational complexity proved itself as not justified considering the minimal error decrease it achieved compared with the simpler methods. However, for future improvement, additional research is needed, such as utilizing low-code machine learning libraries and time-series forecasting techniques.

Cycling is a sustainable and healthy form of transportation that is gradually becoming the primary means of transportation over shorter distances in many countries. This paper describes the dataset used to determine the cycling characteristics of seniors in the USA and Canada. For these purposes, a specially created questionnaire was used in a survey conducted from August 2021 to July 2022. The questionnaire contained sections related to the general socio-demographic characteristics of the respondents, general characteristics of cycling (type of bicycle, cycle time, mileage, etc.), and specific characteristics of cycling (riding in night conditions, termination of cycling, motivating and demotivating factors for cycling, etc.). The total sample consisted of 5096 respondents (50+ years old). This database is particularly significant because it represents the first set of publicly available data related to the cycling characteristics of older adults. The database can be used by various researchers dealing with this topic, but also by the decision-makers who want to design a sustainable and accessible cycling infrastructure, respecting the requirements of this category of users. Finally, this dataset can serve as an adequate basis in the process of determining the specificities and understanding the needs of older cyclists in traffic.

Modern cities and their transportation systems are challenged by new mobility options – micromobility. Electric scooters as the advanced successors of the Segway have flooded the streets of modern cities precisely because of their positive features. They are easy to use, environmentally friendly, faster than traditional public transportation and more compact than a bicycle, allowing users to travel quickly and cheaply and retain complete autonomy of their movement. Regardless of whether they are private vehicles or part of an organized transport service offer, e-scooters are increasingly more important in the daily modal share in urban areas. On the one hand, this seems like a dream come true for the future of mobility, but the reality points to the potential problems that these changes are bringing and which must be addressed appropriately. The street profile has its spatial limitations and usually separates non-motorized and motorized users, and this could be disrupted by new micromobility options. Even in the cases of shared spaces, these vehicles could change the usual mobility pattern. Also, the legislation does not recognize e-scooters and we cannot legally define and protect them, nor we can assign them a place in the street profile. Special attention must be paid to the safety issue for all traffic participants, especially for pedestrians and vulnerable categories. This paper will give a brief overview of the present situation of micromobility in urban areas worldwide and in Serbian cities. Furthermore, it will consider the possibilities and preconditions for its wider use.