• Energy Research

Turbo-roundabouts are one of the most frequently recommended road junction design options when it comes to increasing traffic capacity and traffic safety. This is in particular true of suburban areas, with dominant traffic flow on the main road and moderate traffic flow on the side road. Other intersections handling local traffic and considerably constricting the availability of space are usually located in the vicinity of such intersections. Another factor contributing to the limited availability of land for construction in these locations is the presence of surrounding residential housing. Then, choosing the suitable turbo-roundabout type becomes the main issue. The article presents a case study for the selection of a type of turbo roundabout under the conditions of considerably constricted land availability based on the analysis of the provision of a swept path for the chosen design vehicles. The article considers the standard egg-type turbo-roundabouts, “look-a-like” type turbo-roundabouts, non-standard “flattened” turbo-roundabouts and ellipse-based roundabouts, with non-standard geometries of the truck apron and central island. For each of the analysed roundabout types, setting-out methods were described in detail, allowing the designer to quickly select a type of roundabout suitable for the specific constrained site conditions. This article analyses the applicability of non-standard turbo roundabouts for three area types: LUDA low urbanisation degree area, BA built-up area and CDA highly commercially developed area along the side road, wherever standard roundabouts are not practicable due to constraints imposed by existing buildings, canals or any other obstacles found at the project site.

Contemporary street space upgrade or regeneration projects tend to include setting up home zones that are located in large city suburbs, smaller towns or spas. These home zones feature one-way streets, merging of a pavement and carriageway into one level surface and various traffic calming measures (TCM), including speed tables and traffic circles (TC). Concrete paving blocks are the preferred surfacing material. As part of this study, traffic surveys were carried out in a small seaside spa in Poland to determine the accelerations and decelerations of vehicles passing through four traffic circles that have different central island heights and different streetscape characteristics. A visual assessment of the pavement condition was also carried out. The pavement deformation changes were analysed using 3D models derived on the basis of the terrestrial laser scanning data obtained with the Trimble SX10 scanning total station. The existing pavement structure was analysed as part of this study. Next, the areas that require strengthening were identified based on subsidence and horizontal forces analyses, with the latter calculated from the observed decelerations and accelerations of the passing vehicles. Finally, design guidelines are given for concrete block surfacing in high traffic impact locations.

Quite a number of new metered parking systems have been introduced in recent years by the local authorities of various spa towns in Poland in connection with home zone conversion projects. The traffic signs posted in these locations were limited to the beginning and end of the demarcated parking area. Traffic circle (TC) is an example of traffic calming measures (TCM) used in home zones to slow down the traffic (case study – home zone in a small spa village). This article presents the results of a study investigating the speed reductions obtained with a home zone and traffic circle used as traffic calming measures. The indispensable speed surveys were carried out in relation to this study in two periods: in summer when the streets are crowded with tourists and in September with little pedestrian traffic. Two research hypotheses were formulated as part of the speed data analysis to verify the slowing effect of traffic circle and the relevance of traffic circles design parameters and location, road function and the surrounding streetscape. For each hypothesis statistical analyses were carried out using two nonparametric tests: two-sample Kolmogorov–Smirnov test and median test. The third research hypothesis formulated in this study was related to sustainable development factors related to fuel consumption and traffic-related air pollution including carbon dioxide, carbon monoxide, nitrogen oxide and hydrocarbons. This hypothesis was verified by estimating the amount of air pollution in the home zone under analysis in three different situations (scenarios): in summer with the travel speed reduced by pedestrian traffic to ca. 8–10 km/h and in September with a small number of pedestrians and 20–25 km/h resulting speed between traffic circles, reduced at traffic circle, and in a theoretical 30 km/h zone with 25–30 km/h assumed speed between traffic circles, dropping at traffic circle. These analyses confirmed the appropriateness of traffic circle as a home zone traffic calming measure, as long as its design is based on a detailed analysis of the relevant factors, including location, road function and the surrounding streetscape.

The ever-increasing use of motor vehicles causes a number of traffic safety and community issues, which are particularly severe in cities, accompanied by a scarcity of parking spaces and challenges encountered in road layout alteration projects. The commonly applied solutions include the designation of through streets, the implementation of on-street parking on residential streets, and retrofitted traffic calming measures (TCMs). This article presents the results of the study conducted on a two-way street where the Metered Parking System (MPS) was implemented together with diagonal and parallel parking spaces, refuge islands, horizontal deflection, and lane narrowing by a single-sided chicane. The aim of this study was to identify those TCMs that effectively helped to reduce the island approach speed. The heuristic method was applied to assess the effect of the respective TCMs on reducing the island approach speed, and the key speed reduction determinants were defined using a cause-and-effect diagram and a Pareto chart. The determinants were evaluated with the binary system and tautological inference principles, whereby a determinant was rated as true when it was found in the field, with a simultaneous speed reduction determined in the survey. Determinants that were not confirmed in the field were rated untrue. Comparative analyses were carried out to rate the respective TCMs as effective, moderately effective, or ineffective. In this way, the following three determinants were rated as the most important for speed reduction at refuge islands: free view, visibility of a pedestrian on the right-hand side of the island, and the refuge island surroundings. Although the study was limited to a single street in Poland, the findings may hold true in other countries where similar TCMs are used.