## 1 Introduction  
Traffic volumes are continuously increasing, as evidenced by data from the US Federal Highway Administration, while sudden climate changes due to global warming exacerbate pavement deterioration. This dual impact of rising traffic loads and extreme weather accelerates pavement distress, reducing service life. Asphalt remains the predominant material used for pavement construction worldwide due to its versatility and performance characteristics. The quality of asphalt binder, which acts as the adhesive material in asphalt mixtures, plays a critical role in pavement performance. Consequently, selecting high-performance materials for asphalt pavements is a growing trend in road engineering. To achieve optimal performance under varying climatic and traffic conditions, researchers have explored incorporating modifiers and fillers into petroleum-based asphalt binders [1, 2]. The natural asphalt Trinidad Lake Asphalt (TLA) differs greatly from petroleum asphalt in terms of composition--soluble asphalt and mineral matter makes all the difference. This composition imparts unique characteristics to TLA, such as rigidity, which limits its use as a standalone binder in asphalt mixtures; low penetration values and high softening points arise from the mineral and asphaltene content by weight of the asphalt component [3]; and TLA been used in asphalt products for over a century. A simple refining process ensures a consistent soluble bitumen content in TLA, and its combination of bitumen and mineral components contributes to its advantageous properties, such as outstanding water resistance, chemical stability, and temperature control [4]. Despite its benefits, the hardness of TLA makes it unsuitable as a sole binder in bitumen mixtures. Instead, it is commonly blended with crude oil distilled asphalt in specific ratios. This combination enables TLA to be included into bitumen mixtures without compromising performance even at high temperatures. TLA-modified binders are prevalent in applications such as bituminous concrete (BC), mastic asphalt (MA) pavements, and modern thin bridge pavement systems [5; 6]. These blends demonstrate enhanced stiffness, adhesion, diminished thermal susceptibility, superior resistance to rutting, and improved oxidative aging characteristics. Nonetheless, the augmented rigidity may adversely affect workability, compaction, and could potentially result in premature failures in the field [7]. Researchers have included polymers into asphalt mixtures to help to offset these difficulties. By lowering temperature sensitivity and increasing resistance to permanent deformation, polymers--including plastometers and thermoplastic elastomers--improve asphalt's performance. Early questions about the hot storage stability of bituminous mixtures modified with polymers were mostly answered by later field tests, notably conducted in Texas during the 1970s with interesting findings [8]. Evaluated for their ability to increase temperature and stress resistance in asphalt mixtures are several polymers; among these, SBS is widely preferred for its consistent performance across a broad temperature range [9; 10; 11; 12; 13; 14]. SBS is a thermoplastic elastomer particularly effective in improving pavement performance due to its molecular structure, which forms a three-dimensional network through physical cross-linking. This structure imparts SBS-modified asphalt with excellent strength, elasticity, and enhanced performance under varying temperature conditions. While star-shaped SBS offers a superior high-temperature performance, linear SBS provides a better performance at medium and low temperatures [15; 16; 17; 18; 19]. Despite extensive research on TLA and SBS individually, studies combining PG 64-22 asphalt binder with higher replacement percentages of TLA and SBS remain limited. There is a need to establish the optimal proportions of TLA and SBS to produce high-performance asphalt with enhanced resistance to plastic deformation under heavy loads (3.2 kPa) for extreme climatic conditions.