The Evaluation of a Selected Part of the Road Network in Zilina Region

Žilinským krajom prechádzajú dva medzinárodné cestné koridory Va a VI, ale hustota cestnej siete kraja patrí medzi najmenšie na Slovensku. Cestná sieť je nadmerne zaťažená a hlavné cestné ťahy kraja patria medzi úseky s najvyššou nehodovosťou. Model komunikačnej obsluhy kraja riešený v uplynulých rokoch sa venoval v rámci integrácie dopravných systémov aj cestnej sieti kraja. Príspevok uvádza základné charakteristiky siete, údaje o súčasnej doprave a princípy modelovania dopravy. Základné východiská pre zlepšenie dopravnej situácie sú uvedené v závere na základe hodnotenia súčasného a predpokladaného stavu zaťaženosti siete.

Two international corridors "Va" and "VI" pass through Žilina region, but yet the road network density of the region belongs to the lowest in Slovakia. The road network is loaded excessively and main arteries come under a section with a maximum accident rate. The model of the communication attendance of the region that has been solved recently deals with the road network in the region in the terms of the transportation system integration. The paper presents basic characteristics of the network, information on the present state of the traffic, as well as principles of a traffic modelling process. The main resources for improving the traffic situation based on the evaluation of present situation and forecast for network loading are presented in the conclusion.

The roads network of Žilina region
Transport plays an important, strategic, and decisive role in the economic development of society. The most important objective of building transport infrastructure is creation of a road network with optimum costs and capacity while respecting principles of safety and ecology and social priorities.
Although two international corridors "Va" and "VI" pass through Žilina region, the road network density of the region belongs to the lowest in Slovakia. The slow rate of the motorway network building in the region was caused above all by high financial demands inducing an excessive loading of the present road network. The main arterials come under the section with a maximum accident rate. The geographical character of the country doesn't allow the development of road network at the level corresponding with demographic conditions. Therefore, it is necessary to create a method for enhancing the traffic service on the basis of integration of all transportation systems, not only within the frame of economic rules, but also from a serviceability point of view.
The territory of Žilina region consists of 11 counties with 313 urban agglomerations. The total number of the inhabitants is 692 582. The situation of the region from a national point of view is shown in Tables 1-3 [1]. Detailed information on the road network in the region is presented there, too. Žilina region in a national comparison (to 31 December, 2000) Table 1 The road network in counties of Žilina region (length in km)

Accident rate
An accident rate is one of the most important components of the road network quality evaluation. For a few years Žilina region has belonged to the most questionable territories in Slovakia from a point of view of traffic accidents. In 1999 and 2000 Žilina region was the biggest contributor to the accident rate in Slovakia on the roads of 1 st Ku kritickým cestným ťahom celoštátneho významu ďalej patria úseky ciest I/61, I/64, I/11, II/487, II/517, II/507, II/583 a II/584 (obr. 1). Na území kraja sa nachádza jeden kritický cestný ťah krajského významu a tiež jeden kritický cestný ťah okresného významu [2].
Nr. I/18 belongs to the critical trunk roads of Slovakia from the point of view of accident rate. The sections of the roads Nr.I/61, I/64, I/11, II/487, II/507, II/583 and II/584 belong to the critical trunk roads in Slovakia, too (Fig. 1). One critical trunk road of the regional importance also exists in the area [2].
The critical accident localities (CAL) participate, above all, in the road safety decrease. (CAL are the sections, in which the accident number is higher than the critical number determined by Poisson probability distribution on the basis of the traffic flow and boundary conditions analysis.) More than 30 CALs occur on the observed 1 st and 2 nd class roads, where nearly 19000 traffic accidents and nearly 400 fatal accidents happened during the last 5 years (Table 4).
Overall five RCAL occur in the region and two belonged to the list of RCAL during the last few years. The localities are situated on the roads Nr. I/18, I/61 and II/487. Detailed data with the results of quantification are described in Table 5 The repeated critical accident localities on the 1 st and 2 nd class roads Table 5 Year  Cestná sieť bola modelovaná z ciest I. triedy a niektorých vybraných úsekov ciest II. triedy. Poloha uzlov a ťažísk jednotlivých okrskov zodpovedala postupu modelovania medzioblastných vzťahov [3]. Vlastný proces modelovania zahrňoval nasledovné kroky:

The loading of the road network
The analysis of the carrying capacity was prepared for evaluating the part of the road network in the region. The integrated parts of the 1st class roads were selected and divided into subsections according to the traffic volume. The maximum traffic volume was calculated according to the traffic census from 2000. The volumes were recalculated for the year 2020 for each section with coefficients of the traffic growth. The obtained values are shown in Fig. 2 The data determined on the basis of demographic and socialeconomic analyses obtained from the household interviews in 1999 were also included into the calculation. The road network was modelled from 1 st class and selected 2 nd class roads. The location of nodes and zone centres responds to the modelling system of the inter-zone relations [3]. The process of the modelling included the following steps: Výsledkom modelovania prepravných vzťahov a ich aplikácie na cestnú sieť sú záťažové kartogramy dopravy, spracované pre denné predpokladané intenzity.
q Modelling the road network in the region using the VISUM software. q Calculation of a distance matrix using the nearest road method. q Transformation of the distance matrix to the VISEM software. q Generation of the O-D matrix. q Trip distribution to the road network in VISUM.
The traffic volume diagrams worked out for a daily presumptive volume present the results of the trip distribution model and their application to the road network.

The trip assignment to the road network
The modelled traffic relations were distributed to the road network in the region with a reduced number of urban agglomerations. The outer area was divided into the neighbouring counties, regions, and countries by routing the transport networks. Only the data concerned Žilina region in the form of the origin or destination traffic were used for calculation. The destination traffic from other regions and through traffic from Považská Bystrica and Prievidza were not evaluated because of lack of information. This fact caused a partial under dimensioning of the regional traffic loading. The basic regional roads network is shown in Fig. 3 [4].

Kapacitné posúdenie vybranej časti cestnej siete
Za účelom zhodnotenia skutočného stavu zaťaženia boli ďalej kapacitne posúdené vybraté časti cestnej siete. Teoretické hodnoty prípustnej intenzity v jazdnom pruhu boli porovnané s vypočítanými hodnotami, určenými na základe skutočných intenzít a súčasných stavebných a jazdných podmienok. Porovnanie bolo realizované percentuálnym vyjadrením podielu skutočnej intenzity ku prípustnej hodnote. Hodnotenie úsekov s prekročenou kapacitou je prezentované v tab. 6. Z tabuľky je zrejmé, že z 19 hodnotených úsekov ciest I. triedy v kraji v roku 2000 až 7 úsekov malo prekročenú teoretickú The expected load of the roads network was obtained by an equilibrium procedure of the trip assignment after calculating the O-D matrixes (Fig. 4). The calculated traffic load of the network almost achieves the level observed in 2000 in spite of the through traffic volumes absence. Whence it follows that the deterrence function used in the VISION software does not correspond completely with Slovak conditions. The model values excess also data obtained by a gravity method, namely for the private transport. In case of the public transport the data are comparable. Therefore it is necessary to pay attention to the model calibration for the VISUM software in future analyses.

The capacity analysis of a selected part of the road network
The capacity analysis of the road network in selected parts was realised in order to determine the recent loading state. Theoretical values of an allowable traffic volume in the traffic lane were compared with calculated values determined on the basis of real volumes and recent building and traffic conditions. The comparison was realised by the percent ratio of the real volume to the allowable volume. The evaluation of the sections with overloaded capacity is presented in Table 6.  Obr. 5. Úseky s prekročenou prípustnou intenzitou 6. Odporúčania pre zvýšenie kvality Z uvedenej analýzy vyplýva, že cestná sieť I. triedy na území Žilinského kraja je z hľadiska kapacity v kritickom stave. Rovnaký výsledok vyplýva z analýzy nehodovosti. Preto je nevyhnutné budovanie diaľničnej siete na území kraja v pôvodne stanovených koridoroch, ktoré navyše zodpovedajú medzinárodným koridorom.

Recommendations for quality improvement
From the presented analysis it results that the road network of 1st class in Žilina region is in a critical state from the point of view of capacity. The same result follows from the traffic accident analysis. Therefore it is necessary to build the motorways network in the region namely in the initially determined corridors, which, in addition, correspond to the international corridors.