Resumen
Roadside trees are one of Poland's most serious road safety issues. Since 2009 more than 2800 people have been killed as a result of tree collisions; this represents about 15% of all of Poland's accident fatalities between 2009 and 2013. In some of the country's regions striking a tree caused more than 30% of all road accident fatalities. With no proper regulations, guidelines or examples of good practice, roadside environments are posing a serious danger to safety. Trees pose a particular hazard. The paper analyses and evaluates the following factors which cause safety risks on roadsides with trees: strategic level (historic factors ? tree alleys, high vehicle speeds, lack of road safety standards), tactical level (region, road class, length of road sections with trees, type of section, time), operational level (road narrowing forcing drivers to use the oncoming traffic lane, limited visibility at junctions and exits). The paper will present ways to eliminate risks caused by roadside trees and how effective they are in reference to the three levels: strategic level (ensuring that road layouts are clear and homogenous, vehicles remain in their lane, building safe roadside environments, securing hazardous objects), tactical level (building a new road, cutting down trees, putting in safety barriers, speed management, hazard notification), operational level (improving visibility using special marking or cutting down trees where they affect visibility at junctions, using the ?2-1? layout, speed reduction, special marking). Understanding the effects of roads or roadsides on safety requires a detailed study. Sections of national and regional roads were used as a basis for building models to describe the effects of selected road and traffic factors on road safety measures.