## 4 Discussion  
The Qassim Region reported one of the highest traffic crashes in Saudi Arabia with an increase in fatalities of 24.3% in 2022, which is one of the highest increases in the Kingdom [43]. The situation demands all sorts of road safety measures, including improved USLS. Performance evaluation criteria to appraise the performance of USLS were developed from the literature and based on expert judgment. The first criterion (C\({}_{1}\)), \"design functionality\", was assessed by three sub-criteria, including illumination brightness adequacy (SC\({}_{11}\)), spacing appropriateness (SC\({}_{12}\)), and positioning of advertisement boards (SC\({}_{13}\)). Figure 6 shows that the performance of SC\({}_{11}\) was \"medium to high\", with a crisp performance score of 3.67. Past studies have reported good technical functionality of the thermal and electrical design of LED technology [44]. As almost 90% of the roads of Buraydah City have been installed with LED, the performance is expected to improve with complete LED-based street-lighting. Most of the respondents found the spacing between the poles appropriate, which resulted in a \"medium to high\" performance (3.56) of SC\({}_{12}\). The distance between the two poles of light is 2.5 to 3 times the pole's height in Buraydah City, which is a global standard [9]. The minimum score of 3.13 of SC\({}_{13}\) shows some inappropriate positioning in the densely populated areas (also see Figure 2). Both the frequency and duration of fixations were reported higher in the case of electronic billboards, in comparison to other signs installed along the roadside [10; 45]. The overall \"medium to high\" performance of C\({}_{1}\) suggests a need for improvement, particularly regarding the locations of electronic billboards. The visibility of lane marking (SC\({}_{21}\)), visibility of road pavement and signs (SC\({}_{22}\)), and impact of oncoming vehicle lighting (SC\({}_{23}\)) assessed the second criterion (C\({}_{2}\)), \"visibility adequacy\". The performance of SC\({}_{21}\) was found high, with a score of 3.73, almost in the middle of the high-performance zone. These findings show that there is desirable night-time visibility of lane marking in the study area. As per the Federal Highway Administration (U.S. Department of Transportation), highly maintained and visible marking (SC\({}_{22}\)) and efficient street-lighting reduce crash risk by improving the nighttime visibility for drivers and other users [46]. The performance score of 3.19 for SC\({}_{23}\) shows a medium satisfaction level of road users in the study area, which means that under existing visibility conditions, drivers commonly face difficulties associated with oncoming vehicle lighting. Low headlight beams engender insufficient visibility and a high safety risk, while high beams propagate a disturbing glare to the drivers [47]. Although most of the new vehicle lighting system has increased the optimal photometric performance, it is still essential to establish the luminous intensity limits for high-beam headlights. The results also show room for improvement in the design of medians and barriers in the study area. During USLS renovations, optimizing photometric characteristics of pavement surfaces and lighting design, by studying various scenarios, can improve road safety and energy efficiency [48]. The smart LED-based USLS, properly designed for environmental conditions and pedestrian traffic, can also be adopted as an energy conservation practice [44]. A study by [PERSON] [49] reported no impact of lower luminous fluxes (lighting levels) on visibility levels for vehicles driven at a constant speed under the limits. Hence, USLS can be automated for speed limits, traffic volumes, traffic density, and road and environmental conditions to save up to 40% of energy. Driver satisfaction level (C\({}_{3}\)) was assessed using three sub-criteria, including impact on eyes (SC\({}_{31}\)), lighting performance in bad weather (SC\({}_{32}\)), and road lighting ambiance (SC\({}_{33}\)).