## 1 Introduction  
Rockfall is a common mountain hazard in which mass of any size falls, bounces, or rolls downward from a cliff or slope. Movement is categorized as rapid to extremely rapid and usually the preceding mass is not displaced from its origin [1, 2, 3]. The fall turns into debris fall when the falling material is detrital fragment of size <20 mm for pebbles, >20-200 mm for cobbles, and >200 mm for boulders [4]. On the other hand, toppling is a failure in natural rock slopes characterized as forward rotation of a slope of soil and rock around a fixed point under the influence of gravity or adjacent cracks and fluids [4, 5]. Fractures with extreme climatic conditions of freeze and thaw serve as the main cause of rockfall [6]. Furthermore, human activity such as undercutting for roads, deforestation, and lack of vegetation in arid climatic conditions increases the process of rockfall and landslides [7]. The occurrence of rockfall and toppling becomes significant when it affects human lives and economically hits elements such as livestock, settlements, infrastructure, and transportation [8]. Rockfall hazard and risk assessment is usually carried out qualitatively or quantitatively, depending upon the nature of the problem and data quality and quantity [1; 9; 10; 11; 12; 13; 14; 15; 16]. The quantitative method is a numerical way of evaluating hazard and risk. Quantitative Risk Assessment (QRA) has been developed to quantify the potential losses by considering fatalities, damaged buildings, and infrastructure. Quantitative approaches are usually difficult to carry out due to economic constraints, data availability issues, and most importantly acceptable and tolerable risk thresholds, which differ from country to country [17]. On the other hand, the qualitative method is most commonly applied for hazard and risk assessment because it is easy to use and apply. This approach descriptively defines hazard and risk by assigning appropriate scores or ratings based on the geologic, topographic, climatic, human, and road specific parameters [11; 18; 19]. For instance, if the cumulative score is lower than 300, the slope will be placed in \"low-urgency treatment\", whereas a score >500 requires \"Immediate stabilization work\" [20; 21; 22]. The first-ever method to address the rockfall hazard for transportation corridors was developed by [PERSON] and [PERSON] [23]. Later on, two famous qualitative models were developed, including one by the Canadian National Railway Corporation [24] along with the Rockfall Hazard Rating System by the USA Federal Highway Administration [1; 19; 25; 26]. Qualitatively, rockfall hazard has been assessed extensively in the last few decades [2; 23; 27; 28; 25]. The authors of [11] presented a comprehensive review of all the modified methods adopted in the last two decades by different countries to assess rockfall hazard and risk assessment. These are summarized as: (1) Rock Slope Rating Procedure (RSRP: New York department of transportation), (2) Italian Modification of RHRS (mRHRS), (3) Missouri Rockfall Hazard Rating System (MORFH RS), (4) Ohio Rockfall Hazard Rating Matrix (ORHRM), (5) Tennessee Rockfall Hazard Rating System (TRHRS), (6) Colorado Rockfall Hazard Rating System (CRHRS), (7) Rockfall Hazard Rating for Ontario (RHRON), (8) Rockfall Risk Rating for Settlements (R3S2), (9) Falling Rock Hazard Index (FRHI), (10) Rockfall Risk Rating System (RRRS). In the recent literature, [21] has provided a comparative assessment of three state-of-the-art technologies for rockfall hazard and risk assessment along roads. The potentials and limitations of the modified Rockfall Hazard Rating System (mRHRS), Rockfall Risk Management (ROMA), and Evolving Rockfall Hazard Assessment (ERHA) are thoroughly discussed in his research. Modifications in RHRS models correspond to different purposes and fields of applications. Assessment of transportation corridors, settlements, excavated and natural rock slopes, and open-pit quarries have remained the major purposes of various models.