Skid resistance is a critical aspect for traffic safety since it significantly influences vehicle control and minimizes the distance required for emergency braking. The surface characteristics of pavements play a pivotal role in determining skid resistance. To achieve the optimal skid resistance performance, the pavement must sustain a specific level of friction. Thus, it is advantageous to apply surface treatments in areas that require enhanced friction. This study investigate the impact of factors such as the aggregate source, size, morphological properties, and abrasion levels on the skid resistance and frictional characteristics of a high-friction surface treatment (HFST). A complete investigation was conducted on HFST samples by analyzing the aggregate morphology using the Aggregate Image Measurement System and performing Micro-Deval abrasion testing. The skid resistance was evaluated with the British Pendulum Tester (BPT). The findings revealed that different aggregates and sizes exhibited varying behaviors post-polishing. Notably, fine-sized aggregates demonstrated higher British pendulum number (BPN) values, which indicate superior frictional performance. Models that predicted skid numbers based on the average texture and angularity indices initially demonstrated the balanced influences of both morphological properties before polishing. However, after polishing, the surface texture emerged as the primary determinant of the skid resistance, which overshadowed the angularity’s impact.

The frictional attributes of high friction surface treatment (HFST) play a crucial role in ensuring optimal traffic safety, particularly in wet weather conditions. Friction consists of two important components: adhesion and hysteresis. This research focuses on evaluating these essential factors in HFST using two different aggregates and two distinct sizes by considering various abrasion and polishing methods. To isolate these components for assessment, testing was carried out under various slippery conditions, including dry, wet with water, and wet with water + soap. The inclusion of liquid hand soap in the test procedure effectively minimized or even eliminated the adhesion component’s influence, making it possible to primarily focus on the hysteresis component. Consequently, the British Pendulum Number (BPN) measured in this research predominantly reflected the hysteresis-related friction. The analysis of variance results emphasized the substantial impact of different abrasion and polishing methods on the BPN values obtained under various surface conditions. Notably, Micro-Deval Abrasion (MDA) with 105, 180, and 240 min abrasion exhibited the most pronounced influence on BPN variation and the higher F-value for the MDA 105 min indicated that this specific abrasion time exerted a more significant influence on the variation in BPN values than other factors. Furthermore, the utilization of the Aggregate Image Measurement System yielded valuable insights into the micro-texture of the aggregates. It revealed that the calcined bauxite HFST size is anticipated to provide the rougher surface morphology (texture) on a pavement surface compared with other sources in this study, thereby contributing to high pavement surface friction. The findings from this study contribute to a deeper understanding of the frictional characteristics of HFST under different scenarios, providing valuable insights for optimizing HFST applications to enhance road safety and skid resistance.

High Friction Surface Treatments (HFST) are recognized for their effectiveness in enhancing skid resistance and reducing road accidents. While Epoxy-based HFSTs are widely applied, they present limitations such as compatibility issues with existing pavements, high installation and removal costs, and durability concerns tied to substrate quality. As an alternative to traditional Epoxy-based HFSTs, this study investigated the effects of aggregate gradation as designated by agencies on the performance of asphalt-based HFST. Various aggregate types were assessed to evaluate friction performance and the impact of polishing cycles on non-Epoxy HFST. It was found that adjustments in aggregate size and gradation may be necessary when transitioning to asphalt-based HFSTs, given the different nature of asphalt as more temperature susceptible compared to Epoxy. Various asphalt binder grades were considered in this study. A series of tests, including the British Pendulum Test (BPT), Dynamic Friction Tester (DFT), Circular Track Meter (CTM), Micro-Deval (MD), and Aggregate Imaging Measurement System (AIMS), were conducted to measure Coefficient of Friction (COF), Mean Profile Depth (MPD), texture, and angularity before and after polishing cycles. The results showed that the COF in asphalt-based slabs decreased more significantly than in Epoxy-based slabs as polishing cycles increased for HFST and medium gradations. However, in coarse gradation, the COF of slabs using asphalt-based binder matched or even surpassed that of Epoxy after polishing. Notably, the PG88-16 binder for Calcined Bauxite (CB) had the smallest reduction in COF after 140K polishing cycles, with only a 19% decrease compared to a 23% reduction for Epoxy.

High Friction Surface Treatments (HFSTs) are recognized for enhancing friction between tires and road surfaces, with reduced road accidents being a key benefit. Epoxy-based HFSTs, though widely used, come with challenges like compatibility issues with existing pavements, higher installation and removal costs, and reduced durability tied to substrate quality. Recently, state agencies have increasingly focused on developing asphalt-based alternative binders for HFST applications as highlighted in the National Cooperative Highway Research Program (NCHRP) RFP #NCHRP 10-145. This study introduces asphalt-based HFSTs as an alternative to traditional epoxy-based treatments. Various aggregate types were examined for friction performance and the effect of polishing cycles on asphalt-based HFST. Tests such as the British Pendulum Test (BPT), Dynamic Friction Tester (DFT), and Circular Track Meter (CTM) were conducted to assess the Coefficient of Friction (COF) and Mean Profile Depth (MPD) before and after polishing cycles. Additionally, a Life Cycle Cost Analysis (LCCA) was performed to determine the economic advantages of asphalt-based HFSTs over epoxy treatments. The goal was to develop a method to convert diverse project and material data into comparable outputs like net present value (NPV), enabling comparisons between alternatives. Results from the LCCA demonstrated that the use of specific asphalt-based binders combined with optimized aggregate gradation not only achieves performance levels comparable to traditional HFST options but also improves cost efficiency.

High Friction Surface Treatments (HFSTs) are frequently used to increase skid resistance and reduce collisions, particularly in crash-prone zones, including horizontal curves and intersections. Epoxy-based binders traditionally have been the sole option for HFSTs, but their drawbacks, such as high costs and compatibility challenges, have led to the search for substitute binders, including asphalt-based options. This study investigates the comparative performance of highly modified asphalt-based binders, including polymer-modified, mastic, and highly modified emulsions, in HFST applications using two aggregate types, Calcined Bauxite (CB) and Rhyolite with different gradations, with an emphasis on their frictional properties, durability, and resistance to polishing. Laboratory evaluations, including the Pendulum Tester (BPT), Dynamic Friction Testing Equipment (DFT), Surface Texture Measurement Apparatus (CTM), and Binder Bond Strength Test (BBS), were carried out to examine the Coefficient of Friction (COF), Mean Profile Depth (MPD), and aggregate bonding and retention. In terms of durability and friction, this study indicated that highly modified asphalt-based binders performed better than PG binders and conventional emulsions. The highest BPT values, both prior to and following polishing, were consistently observed for CB, with the emulsion containing the highest reactive polymer modifier showing the smallest decrease in BPT value (12.86% for CB and 10.34% for Rhyolite). Epoxy showed a greater COF retention over lengthy polishing cycles; however, highly polymer-modified (PM) binders like PG82-22 (PM) performed better than Epoxy under specific conditions. The macrotexture analysis revealed that Epoxy-based samples retained surface texture for further polishing cycles, while Mastic2 and PG82-22 (PM) also showed strong MPD retention. These findings highlight the importance of optimizing aggregate–binder combinations to ensure durable and effective HFST applications.