Maanteiden tasoliittymien turvallisuus: Onnettomuudet vuosina 2011-2015

The objective was to update the knowledge of safety at road intersections (at-grade junctions), for inclusion in this study and in road planning instructions. No new re-search results were found that substantially change the perception of what influences the safety of intersections. Different ways of defining intersection accidents were al-so examined, as no internationally recognised definition is found in the literature. This study examined all injury accidents, excluding animal-related accidents that oc-curred no more than 100 m from an intersection in urban areas and maximum 200 m in rural areas. Shorter distances have been used when an accident location was specified to a particular section of road or intersection. Traffic volume on roundabout arms was estimated, as this information is not given in the national road databank. The risk of injury accidents and especially fatalities was higher at four-way than at three-way intersections. Accident costs averaged 5.4 cents and 3.0 per arriving ve-hicle at four-way and three-way intersections, respectively. According to previous research and the results of this study, the risk of injury accidents and fatalities is lower at roundabouts than at three-way intersections, and thus even lower compared to four-way intersections. The accident cost for roundabouts was 2.2 cents per arriv-ing vehicle. Roundabouts are commonly used in urban areas, which might explain some of the differences in accident costs. Number of arriving vehicles and intersection type are the variables that most strong-ly affect the number of accidents at intersections. Accident models confirm the earli-er assumption that as the share of vehicles approaching an intersection from a minor road rises, so does the injury accident risk at both three- and four-way intersections, for both vehicle traffic and vulnerable road users (pedestrians, bicyclists and mo-pedists). However, when a rise in the overall daily amount of approaching vehicle traffic is considered, the accident risk falls for the vehicles but not for vulnerable road users. The risk to vulnerable road users is high, especially on the lower-grade traffic network and in urban areas, both at three- and four-way intersections. The study did not reveal any new information on safety justifications for staggered intersections, or how such staggering would be done. The injury accident risk seems to be lower at intersections staggered right-to-left compared with left-to-right, but the opposite is true regarding fatality risk. In addition to random variation, these differ-ences may depend on how and where the staggering is done. Differences in fatality risk at intersections were mainly attributed to intersection type and speed limit. In the accident model, the fatality risk at four-way intersections in areas with a 100 km/h speed limit was found to be three times higher than in other speed limit areas. Even though, a 100 km/h speed limit is usually only allowed on roads with a high safety level.