The purpose of this study is to implement a rock fall hazard rating system to the cut slopes along Kizilcahamam-Gerede segment of D750 (Ankara-istanbul) Highway. The rating system developed by the Tennessee Department of Transportation was assessed for thirty six cut slopes which were selected based on a reconnaissance survey along D750 highway, between Kurtbogazi Dam (50 km northwest of Ankara) and AktaS village (15 km to Gerede town of Bolu province). The stages of the investigation consist of project conception, field investigations and application of this system, assessment and presentation of data. The cut slopes were classified by implementing this method which requires a scoring on an exponential scale assigned to various parameters related to the site and roadway geometry and geologic characteristics. The rating process was completed at two stages: Preliminary and Detailed Rating. Based on the Tennessee RHRS, nineteen cutslopes were assessed according to these two stages while the other seventeen cut slopes were able to be classified only with the preliminary rating stage. Different modes of slope failure (planar, wedge, toppling, rock fall with differential weathering, raveling) throughout the selected segments of the highway were investigated and the slope and highway related parameters such as slope height, ditch effectiveness, average vehicle risk, road width, percent desicion site distance and rockfall history were identified for these nineteen cut slopes. After the scoring process was completed all cut slopes were classified based on their hazard ratings from the point of the problems that they may cause in transportation. According to the rules of Tennessee RHRS, a total of thirty five cut slopes were rated. Among these slopes, nineteen of them are rated as A slopes which are considered to be potentially hazardous, while a total of seven are rated as C slopes which pose no danger. In placing a slope into a B category, it is considered that they are not as prone as A slopes to create a danger and a total of nine B slopes are detected. The detailed rating is accomplished for these nineteen A slopes and as a result of the scorings, it has been seen that the final RHRS scores range from 164 to 591. The slopes with scores over 500 can be counted as more hazardous slopes since they get very high scores both from site and roadway geometry and geologic hazard part.

On-the-job injuries that occur even after implementing safety interventions highlight the need for identifying the limitations in them and for making future safety interventions and technological advances more effective. One possible reason for this lower-than-expected-safety returns is the latent side-effect of safety interventions, known as risk compensation. This dissertation aimed to provide empirical evidence and theoretical considerations of risk compensation effect in the construction industry. Accordingly, a multi-sensor immersive mixed-reality environment consists of a virtual projection of the environment and passive haptics of a roof was developed to study risk compensation among residential roofers. Simulating height, environmental factors (wind and sound), passive haptic, and virtual falls stimulated sufficient Sense of Presence to trigger subjects' behavioral changes while installing shingles on a 27-degree sloped roof under three levels of safety interventions (i.e., with no fall-safety intervention, with an injury-reducing fall-safety intervention—i.e., fall-arrest system—and with an injury-preventing fall-safety intervention— i.e., a fall-arrest system and a guardrail). The baseline demographic, psychographic, and cognitive measures combined with real-time tracking and wearable sensors provided an opportunity to track the worker's motions, localize his/her position, obtain real-time musculoskeletal data, and monitor the his/her behavioral and physiological responses. The collected data is then translated into information about the risk perception and risk-taking behavior of the worker. The results yielded unequivocal evidence of risk compensation—the lower perceived risk associated with the situation (lower levels of stress) and the false sense of security among roofers when they were provided with safety interventions apparently encouraged them to be less cautious by leaning over the edge, stepping closer to the roof edge, spending more time exposing themselves to fall risk, over-relying on the safety equipment through different facing directions and choices of posture stability. As a result, they also experienced more near-misses (close calls). This behavioral adaptation was more pronounced when they were provided with an injury-preventing safety intervention (e.g., guardrail). The findings also suggested that the productivity and safety benefits of safety interventions can be negated due to risk compensation, which identifies vital information for the construction-safety community to consider during the design and implementation of more effective safety interventions and technological advances. Roofers with high risk tolerance and sensation seekers were identified as high-risk groups who are more likely to be involved in risk-compensatory behaviors; various behavioral interventions are suggested in this dissertation to counteract excessive risk-taking and to reduce risk compensation. The findings of this study shed light on the question of why injury rates have remained at worrisome levels despite advances in protective measures and interventions. In the long-term, a better understanding of risk compensation will translate into fundamental knowledge about how the construction industry should approach and maintain controls after safety interventions. / Doctor of Philosophy / While researchers have dispensed considerable efforts to reduce the risk of occupational injuries by implementing safety interventions, the large number of safety incidents occurring each year in the construction industry. It is hypothesized that the latent effect of safety interventions, known as risk compensation, might be a possible reason why many of the safety interventions and technological advances have not fully achieved their safety objectives. This dissertation aimed to empirically examine the changes in workers' productivity, risk perception, risk-taking behaviors as a function of different safety interventions in place. To study this within a risk-free setting, an immersive mixed-reality environment simulating roofing task was developed. Then, the reactionary behavioral responses of participants were monitored using real-time tracking sensors and qualitative sources of data while they were completing a roofing task under three counterbalanced levels of safety interventions (i.e., with no fall-safety intervention, with an injury-reducing fall-safety intervention—i.e., fall-arrest system—and with an injury-preventing fall-safety intervention— i.e., a fall-arrest system and a guardrail). The findings indicated that the reduced perceived risk and the desire for increased productivity may skew risk analysis and strongly bias workers toward presuming invulnerability when safety interventions are in place. According to risk compensation theory, workers' risk tolerance and perceptions of risk influence their risk-taking behavior—as the perceived risk associated with the situation decreases, individuals take more risks to achieve a level of risk they can comfortably tolerate. Therefore, the workers might become less cautious by leaning over the edge, stepping closer to the roof edge, spending more time exposing themselves to fall risk, over-relying on the safety equipment through different facing directions and choices of posture stability. This result does not necessarily imply the safety innovations are completely ineffective, but rather demonstrates dangers users face when they misperceive the effectiveness of a safety intervention. Furthermore, roofers with high risk tolerance and a high sensation-seeking disposition were identified as high-risk groups who are more likely to be involved in risk-compensatory behaviors. This research represented a substantive departure from the status quo by proposing novel pathways for proactive incident prevention due to risk compensation in the construction industry. The contribution of this study is especially significant because a better understanding of risk compensation will translate into fundamental knowledge about how the construction industry should approach and maintain controls after safety interventions.