To improve the allocation of funds for the maintenance and risk mitigation of transportation infrastructure, there is a dire need for a simplified, yet sufficiently accurate, methodology to estimate bridge vulnerability to scour. The methodology should make use of existing data and indicate the basic variables needed to assess the vulnerability of bridges located around a future expressway in southeastern Serbia. The first part of the paper discusses the identification of possible modes of bridge failure caused by scouring that depend on soil, structure, and river hydraulic properties. The degradation of soil parameters is assumed to be the main cause of bridge failure. The capacity of a bridge to withstand a certain amount of structural damage governs the direct and indirect costs attributable to bridge failure; the subsequent work zones related to rehabilitation reduce the performance of the whole network. In the second part of the paper, a simulation of the redistribution of traffic flows is described for several possible scenarios; the simulations use state-of-the-art software VISUM, which was developed for computer-aided transportation planning and analysis. The simulated scenarios include the partial and full closure of road links as a result of bridge failures. The simulations confirmed that the most significant contribution to indirect costs stems from the increase in the total travel time of all network users.

New Serbian policies on road design introduce the concept of operating speeds. Decades ago, national policies were based on the constant design speed concept. Among other design parameters, in relation to that constant design speed, minimum radii of horizontal and vertical road geometry were determined. Introduction of the operating speed concept provides for more realistic prediction of speed levels along the road. Unlike the constant design speed, operating speed levels vary along the road, reaching higher levels in curves with larger radii, on straight sections and on reverse curves and dropping down to the design speed level in horizontal curves with the minimum radius. Consequently, besides a constant Stopping Sight Distance (SSD), which is calculated from the constant design speed, the new term, Required Sight Distance (RSD) is introduced. RSD varies along the road, as it is calculated from the operating speed, which also varies along the road. Appropriate RSD analyses are crucial on road rehabilitation projects, since a simple resurfacing that enables higher speed levels, without providing increased RSD, may hamper the safety of a newly resurfaced road. Software tools for predicting operating speed levels and optical analyses of the road are also presented in this paper. Software tools for RSD analyses enable the import of lines of sight into the 3D model of the roadway and their export into the cross sections extracted from the model, thus facilitating the obstacle removal. Also demonstrated are tools for determining Available Sight Distance (ASD), which are based on triangulated 3D models of the roadway as well.

In the past, numerous researchers and pavement proffesionals tried to find an analytical relationship between the road roughness and the vehicle speed which were measured on the same test sections. In HDM-4, special models were developed, in which maximum limiting speeds relative to road roughness condition were calculated. In this paper, a brief review of significant research conducted around the world that analyzed the influence of increasing road roughness, expressed through IRI, on the change of vehicle speed values, was given. The benefits and drawbacks of the results from previous studies were outlined, and the most important equations that define the relationship between the IRI and vehicle speed were presented. It has been found that the effect of pavement roughness on the vehicle speed is very small on the roads with IRI values less than 5m/km, such are usually the roads located in most developed countries.

1 Klinika za Ginekologiju i Akušerstvo KBC Priština sa sedištem u Kosovskoj Mitrovici 2 Klinika za Pedijatriju KBC Priština sa sedištem u Kosovskoj Mitrovici Preterminski porođaj u humanoj populaciji je sindrom koji nastaje zbog više uzroka. Pre 30-te nedelje gestacije, infekcija predstavlja glavni uzrok. U kasnijoj gestaciji, prevremena aktivacija HHA osovine je odgovarna za poremećaj intrauterine sredine (hipoksemija, pothranjenost, čak i infekcija). Treći mehanizam uključuje vaskularne trombotične promene. Ispitivanja na ovcama su pokazala da kod prevremenog rađanja postoji značajna promena koja je povezana sa prevremenim povećanjem adenokortikotropnog hormona (ACTH) i kortizola u fetalnoj cirkulaciji, a koje je takođe praćeno i rastom mRNK, proopiomelanokortina (POMC) i prohormona konvertaze-1 (PC-1) u intermedijalnom delu fe-talne hipofize. Ovi različiti mehanizmi mogu delovati odvojeno, ili se aktivirati u isto vreme sa različitim stepenom delovanja kod istog pacijenta. UVOD Jasno je iz dosadašnjih studija da početak porođaja kod mnogih vrsta iniciran od strane fetusa. Kod ovaca, uticaj fetalnog genoma je izražen kroz dva nezavisna ali i povezana puta, fetalni rast i fetalni endokrini put. Tokom trudnoće , rastući fetus progesteronskim delovanjem vrši neprekidan stimulus za razvoj uterusa. U terminu uticaj progesterona opada i aktivira se paket gena odgovornih za aktivaciju miometrijuma kroz povećanje kontraktil-nosti. Fetalni endokrini put obuhvata maturaciju hipota-lamusno-hipofizarno-adrenalnu osovine (HHA), pove-ćavajući stvaranje fetalnog kortizola koji ne samo da stimuliše sazrevanje onih organskih sistema odgovornih za ekstrauterino preživljavanje, već i stimuliše placentnu steroidogenezu. Promena u koncentraciji progesterona prati povećanje koncentracije maternalnog serumskog esterogena i povećanje stvaranja prostaglandina F2alfa (PGF2alfa). Smatra se da fetalni kortizol povećava aktiv-nost prostaglandin sintetaze (PGHS2) u posteljici. To vodi povećanju koncentracije prostaglandina E2 (PGE2) u fe-talnoj cirkulaciji. PGE2 povećava ekspresiju, u fetalnim trofoblastnim ćelijama, p450C17 liase, što može da ukaže da promene u fetalnom endokrinom sistemu vodi povećanju produkcije placentnih steroida [1]. Opisane sekvence početka porođaja kod ovce mogu imati izvanredne sličnosti sa porođajem kod humane populacije. Ključne razlike su odsustvo smanjenja konce-ntracije progesterona, nedostatak indukcije p450C17 lia-ze u posteljici, i da povećanje kortikotropin-rilizing hor-mona (CRH) u humanoj placenti nije u skladu sa pove-ćanjem PGE2. Preterminski porođaj u humanoj populaciji je sin-drom koji nastaje zbog više uzroka. Pre 30-te nedelje gestacije, infekcija predstavlja glavni uzrok. U kasnijoj gestaciji, prevremena aktivacija HHA osovine je odgovarna za poremećaj intrauterine sredine (hipok-semija, pothranjenost, čak i infekcija). Treći mehanizam uključuje vaskularne trombotične promene. Ovi različiti mehanizmi mogu delovati odvojeno, ili se aktivirati u isto vreme sa različitim stepenom delovanja kod istog...

Exits on multilevel interchange ramps present potentially dangerous spots from the point of traffic safety. Therefore, a range of vehicle restraint systems was developed to reduce the consequences of traffic accidents. Proper installation of adequate crash cushion systems requires sufficient space (length) at the point where the ramp leaves major road. To provide for an installation of such a system, the basic geometry of the exit ramp must be reconsidered, introducing the appropriate ration between the radius and transition curve.