# Retrofitting of Bridge Slabs for Safety Railing Refurbishment in Italy: A State-of-the-Art Review
## 1 Introduction  
Road bridge railing failures can have serious consequences on the safety of both motorists and pedestrians [1]. In fact, when these railings fail or are inadequate, various safety issues can arise such as vehicle accidents. The primary purpose of bridge railings is to prevent vehicles from veering off the road and falling from the bridge. When railings fail, it increases the risk of vehicles colliding with the bridge structure, potentially causing severe accidents and injuries. Inadequate bridge railings can lead to fatalities and injuries among occupants of vehicles involved in accidents. The absence of a reliable barrier increases the chances of vehicles plunging off the bridge or striking other vehicles. When bridges are provided with walkways, effects on pedestrians can occur if the bridge railings on these walkways fail. This puts pedestrians at risk of falling from the bridge, which can result in severe injuries or fatalities. In some cases, bridge railings may have design flaws that make them less effective in preventing accidents. Poorly designed railings may not provide adequate containment, allowing vehicles to easily breach them during collisions. Even when design flaws are absent, bridge railings can deteriorate due to factors like weathering, corrosion, and vehicle impacts. Neglected maintenance and poor construction materials can exacerbate this problem. When the railings (or their connection to the bridge) degrade, their ability to withstand vehicle impacts and protect them against accidents diminishes. In order to cover these gaps, both Italian and European authorities issued new codes pertaining to the evaluation and certification of the adequacy of new safety railings. Severalcodes on this topic have been issued in Italy since 1992 [2; 3; 4; 5], and the European code EN1317 was adopted in Italy and other EU countries [6; 7; 8]. This normative framework, which is related to new road infrastructure construction, allows existing infrastructure to adopt old safety railings. Due to this and the above-mentioned technical issues, poor-quality safety railings on older bridges may be a contributing cause to some of the major accidents observed in the last decade in Italy. For example, the recent accident of Mestre (Italy), which caused 21 fatalities and 15 injuries, is one of the most tragic road accidents that recently occurred in Italy. A bus fell from a bridge (the so-called Vampa overpass) equipped with a very old safety rail. Moreover, in the accident zone, the railing was interrupted, and most probably this facilitated the bus to overcome the parapet and fall. This tragedy strongly highlighted the need of railing retrofitting interventions along Italian roads, especially those with high traffic volume. Neglecting the causes of the vehicle skid, which are under investigation, a simple engineering analysis can easily confirm that the presence of an up-to-date barrier could have avoided or mitigated the tragedy. Another accident happened on 28 July 2013, when another bus fell from the Acqualonga bridge along the A16 motorway in southern Italy. A total of 40 people died and 8 were injured. In this case, the bus lost the brakes, and the bridge barriers failed due to the impact [9]. These two tragedies, similar to each other, caused 62 fatalities, more than the complete collapse of 250 long Morandi bridge span [10] responsible for 43 fatalities. Therefore, accidents due to the collapse of safety railings can have a human life cost similar to great natural disasters, such as earthquakes [11; 12], and thus should not be considered minor issues with respect to the global safety of bridges. Despite this fact, the importance of bridge railings is not fully recognized by the Italian technical code [13]. The recent Italian guidelines on risk classification and management of road bridges [14] are devoted to assigning the \"class of attention\" (a kind of risk evaluation) to all road bridges through a multilevel evaluation based on documental analysis and accurate inspections.